fix no_std building

* Avoid temporary allocation when push locals during function invocation.

* Extend value stack for all locals at once.

.cargo/config

@@ -0,0 +1,2 @@
+[target.armv7-unknown-linux-gnueabihf]
+linker = "arm-linux-gnueabihf-gcc"

.editorconfig

@@ -1,11 +1,9 @@
 root = true
 [*]
-indent_style=tab
-indent_size=tab
-tab_width=4
+indent_style=space
+indent_size = 4
 end_of_line=lf
 charset=utf-8
 trim_trailing_whitespace=true
 max_line_length=120
 insert_final_newline=true
-

.gitignore

@@ -3,3 +3,4 @@
 **/*.rs.bk
 Cargo.lock
 spec/target
+.idea

.travis.yml

@@ -1,32 +1,36 @@
-dist: trusty
-sudo: required
+dist: xenial
+
 language:
 - rust
 - cpp
-rust:
-  - nightly
-  - stable
-addons:
-  apt:
-    sources:
-    - ubuntu-toolchain-r-test
-    packages:
-    - gcc-6
-    - g++-6
-    - cmake
-env:
-- CC=/usr/bin/gcc-6 CXX=/usr/bin/g++-6
+
+matrix:
+  fast_finish: true
+  include:
+  - rust: nightly
+  - rust: stable
+  - rust: stable
+    env: TARGET=armv7-unknown-linux-gnueabihf
 
 install:
-# Install `cargo-deadlinks` unless it is currently installed.
-- command -v cargo-deadlinks &> /dev/null || cargo install cargo-deadlinks
 - if [ "$TRAVIS_RUST_VERSION" == "nightly" ]; then rustup target add wasm32-unknown-unknown; fi
+- if [ -n "$TARGET" ]; then rustup target add "$TARGET" && sudo apt-get install --yes qemu-user-static; fi
+- if [ "$TARGET" == "armv7-unknown-linux-gnueabihf" ]; then sudo apt-get install --yes crossbuild-essential-armhf && export QEMU_LD_PREFIX=/usr/arm-linux-gnueabihf; fi
+- rustup component add rustfmt
+- sudo apt-get install --yes cmake
+
 script:
+- cargo fmt --all -- --check
 # Make sure nightly targets are not broken.
 - if [ "$TRAVIS_RUST_VERSION" == "nightly" ]; then cargo check --tests --manifest-path=fuzz/Cargo.toml; fi
 - if [ "$TRAVIS_RUST_VERSION" == "nightly" ]; then cargo check --benches --manifest-path=benches/Cargo.toml; fi
-- ./test.sh
+# Make sure `no_std` version checks.
+- if [ "$TRAVIS_RUST_VERSION" == "nightly" ]; then cargo +nightly check --no-default-features --features core; fi
+# Check that `vec_memory` feature works.
+- cargo check --features vec_memory
+- travis_wait 60 ./test.sh
 - ./doc.sh
+
 after_success: |
   # Build documentation and deploy it to github pages.
   [ $TRAVIS_BRANCH = master ] &&
@@ -35,7 +39,18 @@ after_success: |
   sudo pip install ghp-import &&
   ghp-import -n target/doc &&
   git push -fq https://${GH_TOKEN}@github.com/${TRAVIS_REPO_SLUG}.git gh-pages
-cache: cargo
+
+cache:
+  # Don't use `cache: cargo` since it adds the `target` directory and that can be huge.
+  # Saving and loading this directory dwarfes actual compilation and test times. But what is more
+  # important, is that travis timeouts the build since the job doesn't produce any output for more
+  # than 10 minutes.
+  #
+  # So we just cache ~/.cargo directory
+  directories:
+    - /home/travis/.cargo
 before_cache:
   # Travis can't cache files that are not readable by "others"
   - chmod -R a+r $HOME/.cargo
+  # According to the Travis CI docs for building Rust project this is done by,
+  - rm -rf /home/travis/.cargo/registry

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "wasmi"
-version = "0.2.0"
+version = "0.5.1"
 authors = ["Nikolay Volf <nikvolf@gmail.com>", "Svyatoslav Nikolsky <svyatonik@yandex.ru>", "Sergey Pepyakin <s.pepyakin@gmail.com>"]
 license = "MIT/Apache-2.0"
 readme = "README.md"
@@ -11,11 +11,42 @@ keywords = ["wasm", "webassembly", "bytecode", "interpreter"]
 exclude = [ "/res/*", "/tests/*", "/fuzz/*", "/benches/*" ]
 
 [dependencies]
-parity-wasm = "0.27"
-byteorder = "1.0"
+wasmi-validation = { version = "0.2", path = "validation", default-features = false }
+parity-wasm = { version = "0.40.1", default-features = false }
 memory_units = "0.3.0"
-nan-preserving-float = "0.1.0"
+libm = { version = "0.1.2", optional = true }
+num-rational = { version = "0.2.2", default-features = false }
+num-traits = { version = "0.2.8", default-features = false }
 
 [dev-dependencies]
 assert_matches = "1.1"
-wabt = "0.3"
+rand = "0.4.2"
+wabt = "0.9"
+
+[features]
+default = ["std"]
+# Disable for no_std support
+std = [
+    "parity-wasm/std",
+    "wasmi-validation/std",
+    "num-rational/std",
+    "num-rational/bigint-std",
+    "num-traits/std"
+]
+# Enable for no_std support
+core = [
+    # `core` doesn't support vec_memory
+    "vec_memory",
+    "wasmi-validation/core",
+    "libm"
+]
+# Enforce using the linear memory implementation based on `Vec` instead of
+# mmap on unix systems.
+#
+# Useful for tests and if you need to minimize unsafe usage at the cost of performance on some
+# workloads.
+vec_memory = []
+
+[workspace]
+members = ["validation"]
+exclude = ["benches"]

README.md

@@ -3,11 +3,41 @@
 
 # `wasmi`
 
-WASM interpreter (previously lived in [parity-wasm](https://github.com/paritytech/parity-wasm))
+`wasmi` - a Wasm interpreter.
 
-Primary purpose of `wasmi` is to be used with [parity](https://github.com/paritytech/parity) (ethereum-like contracts in wasm) and with [Polkadot](https://github.com/paritytech/polkadot). However, `wasmi` is designed to be as flexible as possible and might be suited well for other purposes.
+`wasmi` was conceived as a component of [parity-ethereum](https://github.com/paritytech/parity-ethereum) (ethereum-like contracts in wasm) and [substrate](https://github.com/paritytech/substrate). These projects are related to blockchain and require a high degree of correctness, even if that might be over conservative. This specifically means that we are not trying to be involved in any implementation of any of work-in-progress Wasm proposals. We are also trying to be as close as possible to the spec, which means we are trying to avoid features that is not directly supported by the spec. This means that it is flexible on the one hand and on the other hand there shouldn't be a problem migrating to another spec compliant execution engine.
 
-At the moment, the API is rather low-level (especially, in the part related to host functions). But some high-level API is on the roadmap.
+With all that said, `wasmi` should be a good option for initial prototyping.
+
+# Build & Test
+
+As `wasmi` contains a git submodule, you need to use `--recursive` for cloning or to checkout the submodule explicitly, otherwise the testing would fail.
+
+```
+git clone https://github.com/paritytech/wasmi.git --recursive
+cd wasmi
+cargo build
+cargo test
+```
+
+# `no_std` support
+
+This crate supports `no_std` environments.
+Enable the `core` feature and disable default features:
+```toml
+[dependencies]
+wasmi = {
+	version = "*",
+	default-features = false,
+	features = "core"
+}
+```
+
+The `core` feature requires the `core` and `alloc` libraries and a nightly compiler.
+Also, code related to `std::error` is disabled.
+
+Floating point operations in `no_std` use [`libm`](https://crates.io/crates/libm), which sometimes panics in debug mode (https://github.com/japaric/libm/issues/4).
+So make sure to either use release builds or avoid WASM with floating point operations, for example by using [`deny_floating_point`](https://docs.rs/wasmi/0.4.0/wasmi/struct.Module.html#method.deny_floating_point).
 
 # License
 

benches/.gitignore

@@ -1 +1,3 @@
 /target
+*.trace
+

benches/Cargo.toml

@@ -6,4 +6,7 @@ authors = ["Sergey Pepyakin <s.pepyakin@gmail.com>"]
 [dependencies]
 wasmi = { path = ".." }
 assert_matches = "1.2"
-wabt = "0.3"
+wabt = "0.9"
+
+[profile.bench]
+debug = true

benches/build.rs

@@ -1,32 +1,31 @@
 use std::env;
 use std::process;
 
-
 fn main() {
-	println!("cargo:rerun-if-changed=./wasm-kernel/");
+    println!("cargo:rerun-if-changed=./wasm-kernel/");
 
-	// The CARGO environment variable provides a path to the executable that
-	// runs this build process.
-	let cargo_bin = env::var("CARGO").expect("CARGO env variable should be defined");
+    // The CARGO environment variable provides a path to the executable that
+    // runs this build process.
+    let cargo_bin = env::var("CARGO").expect("CARGO env variable should be defined");
 
-	// Build a release version of wasm-kernel. The code in the output wasm binary
-	// will be used in benchmarks.
-	let output = process::Command::new(cargo_bin)
-		.arg("build")
-		.arg("--target=wasm32-unknown-unknown")
-		.arg("--release")
-		.arg("--manifest-path=./wasm-kernel/Cargo.toml")
-		.arg("--verbose")
-		.output()
-		.expect("failed to execute `cargo`");
+    // Build a release version of wasm-kernel. The code in the output wasm binary
+    // will be used in benchmarks.
+    let output = process::Command::new(cargo_bin)
+        .arg("build")
+        .arg("--target=wasm32-unknown-unknown")
+        .arg("--release")
+        .arg("--manifest-path=./wasm-kernel/Cargo.toml")
+        .arg("--verbose")
+        .output()
+        .expect("failed to execute `cargo`");
 
-	if !output.status.success() {
-		let msg = format!(
-			"status: {status}\nstdout: {stdout}\nstderr: {stderr}\n",
-			status=output.status,
-			stdout=String::from_utf8_lossy(&output.stdout),
-			stderr=String::from_utf8_lossy(&output.stderr),
-		);
-		panic!("{}", msg);
-	}
+    if !output.status.success() {
+        let msg = format!(
+            "status: {status}\nstdout: {stdout}\nstderr: {stderr}\n",
+            status = output.status,
+            stdout = String::from_utf8_lossy(&output.stdout),
+            stderr = String::from_utf8_lossy(&output.stderr),
+        );
+        panic!("{}", msg);
+    }
 }

benches/src/lib.rs

@@ -13,7 +13,7 @@ use wasmi::{ImportsBuilder, Module, ModuleInstance, NopExternals, RuntimeValue};
 use test::Bencher;
 
 // Load a module from a file.
-fn load_from_file(filename: &str) -> Result<Module, Box<error::Error>> {
+fn load_from_file(filename: &str) -> Result<Module, Box<dyn error::Error>> {
 	use std::io::prelude::*;
 	let mut file = File::open(filename)?;
 	let mut buf = Vec::new();

benches/wasm-kernel/src/lib.rs

@@ -33,7 +33,7 @@ pub extern "C" fn prepare_tiny_keccak() -> *const TinyKeccakTestData {
 }
 
 #[no_mangle]
-pub extern "C" fn bench_tiny_keccak(test_data: *const TinyKeccakTestData) {
+pub extern "C" fn bench_tiny_keccak(test_data: *mut TinyKeccakTestData) {
 	unsafe {
 		let mut keccak = Keccak::new_keccak256();
 		keccak.update((*test_data).data);

examples/interpret.rs

@@ -4,14 +4,14 @@ extern crate wasmi;
 
 use std::env::args;
 use std::fs::File;
-use wasmi::{ModuleInstance, NopExternals, RuntimeValue, ImportsBuilder, Module};
+use wasmi::{ImportsBuilder, Module, ModuleInstance, NopExternals, RuntimeValue};
 
 fn load_from_file(filename: &str) -> Module {
-	use std::io::prelude::*;
-	let mut file = File::open(filename).unwrap();
-	let mut buf = Vec::new();
-	file.read_to_end(&mut buf).unwrap();
-	Module::from_buffer(buf).unwrap()
+    use std::io::prelude::*;
+    let mut file = File::open(filename).unwrap();
+    let mut buf = Vec::new();
+    file.read_to_end(&mut buf).unwrap();
+    Module::from_buffer(buf).unwrap()
 }
 
 fn main() {
@@ -27,10 +27,10 @@ fn main() {
     let module = load_from_file(&args[1]);
 
     // Intialize deserialized module. It adds module into It expects 3 parameters:
-     // - a name for the module
-     // - a module declaration
-     // - "main" module doesn't import native module(s) this is why we don't need to provide external native modules here
-     // This test shows how to implement native module https://github.com/NikVolf/parity-wasm/blob/master/src/interpreter/tests/basics.rs#L197
+    // - a name for the module
+    // - a module declaration
+    // - "main" module doesn't import native module(s) this is why we don't need to provide external native modules here
+    // This test shows how to implement native module https://github.com/NikVolf/parity-wasm/blob/master/src/interpreter/tests/basics.rs#L197
     let main = ModuleInstance::new(&module, &ImportsBuilder::default())
         .expect("Failed to instantiate module")
         .run_start(&mut NopExternals)
@@ -40,5 +40,8 @@ fn main() {
     let argument: i32 = args[2].parse().expect("Integer argument required");
 
     // "_call" export of function to be executed with an i32 argument and prints the result of execution
-    println!("Result: {:?}", main.invoke_export("_call", &[RuntimeValue::I32(argument)], &mut NopExternals));
+    println!(
+        "Result: {:?}",
+        main.invoke_export("_call", &[RuntimeValue::I32(argument)], &mut NopExternals)
+    );
 }

examples/invoke.rs

@@ -3,9 +3,8 @@ extern crate wasmi;
 
 use std::env::args;
 
-use parity_wasm::elements::{Internal, External, Type, FunctionType, ValueType};
-use wasmi::{RuntimeValue, ModuleInstance, NopExternals, ImportsBuilder};
-
+use parity_wasm::elements::{External, FunctionType, Internal, Type, ValueType};
+use wasmi::{ImportsBuilder, ModuleInstance, NopExternals, RuntimeValue};
 
 fn main() {
     let args: Vec<_> = args().collect();
@@ -23,14 +22,19 @@ fn main() {
         // Export section has an entry with a func_name with an index inside a module
         let export_section = module.export_section().expect("No export section found");
         // It's a section with function declarations (which are references to the type section entries)
-        let function_section = module.function_section().expect("No function section found");
+        let function_section = module
+            .function_section()
+            .expect("No function section found");
         // Type section stores function types which are referenced by function_section entries
         let type_section = module.type_section().expect("No type section found");
 
         // Given function name used to find export section entry which contains
         // an `internal` field which points to the index in the function index space
-        let found_entry = export_section.entries().iter()
-            .find(|entry| func_name == entry.field()).expect(&format!("No export with name {} found", func_name));
+        let found_entry = export_section
+            .entries()
+            .iter()
+            .find(|entry| func_name == entry.field())
+            .expect(&format!("No export with name {} found", func_name));
 
         // Function index in the function index space (internally-defined + imported)
         let function_index: usize = match found_entry.internal() {
@@ -41,11 +45,14 @@ fn main() {
         // We need to count import section entries (functions only!) to subtract it from function_index
         // and obtain the index within the function section
         let import_section_len: usize = match module.import_section() {
-            Some(import) =>
-                import.entries().iter().filter(|entry| match entry.external() {
+            Some(import) => import
+                .entries()
+                .iter()
+                .filter(|entry| match entry.external() {
                     &External::Function(_) => true,
                     _ => false,
-                    }).count(),
+                })
+                .count(),
             None => 0,
         };
 
@@ -53,7 +60,8 @@ fn main() {
         let function_index_in_section = function_index - import_section_len;
 
         // Getting a type reference from a function section entry
-        let func_type_ref: usize = function_section.entries()[function_index_in_section].type_ref() as usize;
+        let func_type_ref: usize =
+            function_section.entries()[function_index_in_section].type_ref() as usize;
 
         // Use the reference to get an actual function type
         let function_type: &FunctionType = match &type_section.types()[func_type_ref] {
@@ -61,12 +69,35 @@ fn main() {
         };
 
         // Parses arguments and constructs runtime values in correspondence of their types
-        function_type.params().iter().enumerate().map(|(i, value)| match value {
-            &ValueType::I32 => RuntimeValue::I32(program_args[i].parse::<i32>().expect(&format!("Can't parse arg #{} as i32", program_args[i]))),
-            &ValueType::I64 => RuntimeValue::I64(program_args[i].parse::<i64>().expect(&format!("Can't parse arg #{} as i64", program_args[i]))),
-            &ValueType::F32 => RuntimeValue::F32(program_args[i].parse::<f32>().expect(&format!("Can't parse arg #{} as f32", program_args[i])).into()),
-            &ValueType::F64 => RuntimeValue::F64(program_args[i].parse::<f64>().expect(&format!("Can't parse arg #{} as f64", program_args[i])).into()),
-        }).collect::<Vec<RuntimeValue>>()
+        function_type
+            .params()
+            .iter()
+            .enumerate()
+            .map(|(i, value)| match value {
+                &ValueType::I32 => RuntimeValue::I32(
+                    program_args[i]
+                        .parse::<i32>()
+                        .expect(&format!("Can't parse arg #{} as i32", program_args[i])),
+                ),
+                &ValueType::I64 => RuntimeValue::I64(
+                    program_args[i]
+                        .parse::<i64>()
+                        .expect(&format!("Can't parse arg #{} as i64", program_args[i])),
+                ),
+                &ValueType::F32 => RuntimeValue::F32(
+                    program_args[i]
+                        .parse::<f32>()
+                        .expect(&format!("Can't parse arg #{} as f32", program_args[i]))
+                        .into(),
+                ),
+                &ValueType::F64 => RuntimeValue::F64(
+                    program_args[i]
+                        .parse::<f64>()
+                        .expect(&format!("Can't parse arg #{} as f64", program_args[i]))
+                        .into(),
+                ),
+            })
+            .collect::<Vec<RuntimeValue>>()
     };
 
     let loaded_module = wasmi::Module::from_parity_wasm_module(module).expect("Module to be valid");
@@ -81,5 +112,9 @@ fn main() {
         .run_start(&mut NopExternals)
         .expect("Failed to run start function in module");
 
-    println!("Result: {:?}", main.invoke_export(func_name, &args, &mut NopExternals).expect(""));
+    println!(
+        "Result: {:?}",
+        main.invoke_export(func_name, &args, &mut NopExternals)
+            .expect("")
+    );
 }

examples/tictactoe.rs

@@ -1,256 +1,255 @@
-extern crate wasmi;
 extern crate parity_wasm;
+extern crate wasmi;
 
 use std::env;
 use std::fmt;
 use std::fs::File;
 use wasmi::{
-	Error as InterpreterError, ModuleInstance, ModuleRef,
-	Externals, RuntimeValue, FuncRef, ModuleImportResolver,
-	FuncInstance, HostError, ImportsBuilder, Signature, ValueType,
-	RuntimeArgs, Trap,
+    Error as InterpreterError, Externals, FuncInstance, FuncRef, HostError, ImportsBuilder,
+    ModuleImportResolver, ModuleInstance, ModuleRef, RuntimeArgs, RuntimeValue, Signature, Trap,
+    ValueType,
 };
 
 #[derive(Debug)]
 pub enum Error {
-	OutOfRange,
-	AlreadyOccupied,
-	Interpreter(InterpreterError),
+    OutOfRange,
+    AlreadyOccupied,
+    Interpreter(InterpreterError),
 }
 
 impl fmt::Display for Error {
-	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-		write!(f, "{:?}", self)
-	}
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{:?}", self)
+    }
 }
 
 impl From<InterpreterError> for Error {
-	fn from(e: InterpreterError) -> Self {
-		Error::Interpreter(e)
-	}
+    fn from(e: InterpreterError) -> Self {
+        Error::Interpreter(e)
+    }
 }
 
 impl HostError for Error {}
 
 mod tictactoe {
-	use super::Error;
+    use super::Error;
 
-	#[derive(Copy, Clone, Debug, PartialEq, Eq)]
-	pub enum Player {
-		X,
-		O,
-	}
+    #[derive(Copy, Clone, Debug, PartialEq, Eq)]
+    pub enum Player {
+        X,
+        O,
+    }
 
-	#[derive(Copy, Clone, Debug, PartialEq, Eq)]
-	pub enum GameResult {
-		Draw,
-		Won(Player),
-	}
+    #[derive(Copy, Clone, Debug, PartialEq, Eq)]
+    pub enum GameResult {
+        Draw,
+        Won(Player),
+    }
 
-	impl Player {
-		pub fn into_i32(maybe_player: Option<Player>) -> i32 {
-			match maybe_player {
-				None => 0,
-				Some(Player::X) => 1,
-				Some(Player::O) => 2,
-			}
-		}
-	}
+    impl Player {
+        pub fn into_i32(maybe_player: Option<Player>) -> i32 {
+            match maybe_player {
+                None => 0,
+                Some(Player::X) => 1,
+                Some(Player::O) => 2,
+            }
+        }
+    }
 
-	#[derive(Debug)]
-	pub struct Game {
-		board: [Option<Player>; 9],
-	}
+    #[derive(Debug)]
+    pub struct Game {
+        board: [Option<Player>; 9],
+    }
 
-	impl Game {
-		pub fn new() -> Game {
-			Game {
-				board: [None; 9],
-			}
-		}
+    impl Game {
+        pub fn new() -> Game {
+            Game { board: [None; 9] }
+        }
 
-		pub fn set(&mut self, idx: i32, player: Player) -> Result<(), Error> {
-			if idx < 0 || idx > 9 {
-				return Err(Error::OutOfRange);
-			}
-			if self.board[idx as usize] != None {
-				return Err(Error::AlreadyOccupied);
-			}
-			self.board[idx as usize] = Some(player);
-			Ok(())
-		}
+        pub fn set(&mut self, idx: i32, player: Player) -> Result<(), Error> {
+            if idx < 0 || idx > 9 {
+                return Err(Error::OutOfRange);
+            }
+            if self.board[idx as usize] != None {
+                return Err(Error::AlreadyOccupied);
+            }
+            self.board[idx as usize] = Some(player);
+            Ok(())
+        }
 
-		pub fn get(&self, idx: i32) -> Result<Option<Player>, Error> {
-			if idx < 0 || idx > 9 {
-				return Err(Error::OutOfRange);
-			}
-			Ok(self.board[idx as usize])
-		}
+        pub fn get(&self, idx: i32) -> Result<Option<Player>, Error> {
+            if idx < 0 || idx > 9 {
+                return Err(Error::OutOfRange);
+            }
+            Ok(self.board[idx as usize])
+        }
 
-		pub fn game_result(&self) -> Option<GameResult> {
-			// 0, 1, 2
-			// 3, 4, 5
-			// 6, 7, 8
-			let patterns = &[
-				// Rows
-				(0, 1, 2),
-				(3, 4, 5),
-				(6, 7, 8),
+        pub fn game_result(&self) -> Option<GameResult> {
+            // 0, 1, 2
+            // 3, 4, 5
+            // 6, 7, 8
+            let patterns = &[
+                // Rows
+                (0, 1, 2),
+                (3, 4, 5),
+                (6, 7, 8),
+                // Columns
+                (0, 3, 6),
+                (1, 4, 7),
+                (2, 5, 8),
+                // Diagonals
+                (0, 4, 8),
+                (2, 4, 6),
+            ];
 
-				// Columns
-				(0, 3, 6),
-				(1, 4, 7),
-				(2, 5, 8),
+            // Returns Some(player) if all cells contain same Player.
+            let all_same = |i1: usize, i2: usize, i3: usize| -> Option<Player> {
+                if self.board[i1].is_none() {
+                    return None;
+                }
+                if self.board[i1] == self.board[i2] && self.board[i2] == self.board[i3] {
+                    return self.board[i1];
+                }
+                None
+            };
 
-				// Diagonals
-				(0, 4, 8),
-				(2, 4, 6),
-			];
+            for &(i1, i2, i3) in patterns {
+                if let Some(player) = all_same(i1, i2, i3) {
+                    return Some(GameResult::Won(player));
+                }
+            }
 
-			// Returns Some(player) if all cells contain same Player.
-			let all_same = |i1: usize, i2: usize, i3: usize| -> Option<Player> {
-				if self.board[i1].is_none() {
-					return None;
-				}
-				if self.board[i1] == self.board[i2] && self.board[i2] == self.board[i3] {
-					return self.board[i1];
-				}
-				None
-			};
-
-			for &(i1, i2, i3) in patterns {
-				if let Some(player) = all_same(i1, i2, i3) {
-					return Some(GameResult::Won(player));
-				}
-			}
-
-			// Ok, there is no winner. Check if it's draw.
-			let all_occupied = self.board.iter().all(|&cell| cell.is_some());
-			if all_occupied {
-				Some(GameResult::Draw)
-			} else {
-				// Nah, there are still empty cells left.
-				None
-			}
-		}
-	}
+            // Ok, there is no winner. Check if it's draw.
+            let all_occupied = self.board.iter().all(|&cell| cell.is_some());
+            if all_occupied {
+                Some(GameResult::Draw)
+            } else {
+                // Nah, there are still empty cells left.
+                None
+            }
+        }
+    }
 }
 
 struct Runtime<'a> {
-	player: tictactoe::Player,
-	game: &'a mut tictactoe::Game,
+    player: tictactoe::Player,
+    game: &'a mut tictactoe::Game,
 }
 
 const SET_FUNC_INDEX: usize = 0;
 const GET_FUNC_INDEX: usize = 1;
 
 impl<'a> Externals for Runtime<'a> {
-	fn invoke_index(
-		&mut self,
-		index: usize,
-		args: RuntimeArgs,
-	) -> Result<Option<RuntimeValue>, Trap> {
-		match index {
-			SET_FUNC_INDEX => {
-				let idx: i32 = args.nth(0);
-				self.game.set(idx, self.player)?;
-				Ok(None)
-			}
-			GET_FUNC_INDEX => {
-				let idx: i32 = args.nth(0);
-				let val: i32 = tictactoe::Player::into_i32(self.game.get(idx)?);
-				Ok(Some(val.into()))
-			}
-			_ => panic!("unknown function index")
-		}
-	}
+    fn invoke_index(
+        &mut self,
+        index: usize,
+        args: RuntimeArgs,
+    ) -> Result<Option<RuntimeValue>, Trap> {
+        match index {
+            SET_FUNC_INDEX => {
+                let idx: i32 = args.nth(0);
+                self.game.set(idx, self.player)?;
+                Ok(None)
+            }
+            GET_FUNC_INDEX => {
+                let idx: i32 = args.nth(0);
+                let val: i32 = tictactoe::Player::into_i32(self.game.get(idx)?);
+                Ok(Some(val.into()))
+            }
+            _ => panic!("unknown function index"),
+        }
+    }
 }
 
 struct RuntimeModuleImportResolver;
 
 impl<'a> ModuleImportResolver for RuntimeModuleImportResolver {
-	fn resolve_func(
-		&self,
-		field_name: &str,
-		_signature: &Signature,
-	) -> Result<FuncRef, InterpreterError> {
-		let func_ref = match field_name {
-			"set" => {
-				FuncInstance::alloc_host(Signature::new(&[ValueType::I32][..], None), SET_FUNC_INDEX)
-			},
-			"get" => FuncInstance::alloc_host(Signature::new(&[ValueType::I32][..], Some(ValueType::I32)), GET_FUNC_INDEX),
-			_ => return Err(
-				InterpreterError::Function(
-					format!("host module doesn't export function with name {}", field_name)
-				)
-			)
-		};
-		Ok(func_ref)
-	}
+    fn resolve_func(
+        &self,
+        field_name: &str,
+        _signature: &Signature,
+    ) -> Result<FuncRef, InterpreterError> {
+        let func_ref = match field_name {
+            "set" => FuncInstance::alloc_host(
+                Signature::new(&[ValueType::I32][..], None),
+                SET_FUNC_INDEX,
+            ),
+            "get" => FuncInstance::alloc_host(
+                Signature::new(&[ValueType::I32][..], Some(ValueType::I32)),
+                GET_FUNC_INDEX,
+            ),
+            _ => {
+                return Err(InterpreterError::Function(format!(
+                    "host module doesn't export function with name {}",
+                    field_name
+                )));
+            }
+        };
+        Ok(func_ref)
+    }
 }
 
 fn instantiate(path: &str) -> Result<ModuleRef, Error> {
-	let module = {
-		use std::io::prelude::*;
-		let mut file = File::open(path).unwrap();
-		let mut wasm_buf = Vec::new();
-		file.read_to_end(&mut wasm_buf).unwrap();
-		wasmi::Module::from_buffer(&wasm_buf)?
-	};
+    let module = {
+        use std::io::prelude::*;
+        let mut file = File::open(path).unwrap();
+        let mut wasm_buf = Vec::new();
+        file.read_to_end(&mut wasm_buf).unwrap();
+        wasmi::Module::from_buffer(&wasm_buf)?
+    };
 
-	let mut imports = ImportsBuilder::new();
-	imports.push_resolver("env", &RuntimeModuleImportResolver);
+    let mut imports = ImportsBuilder::new();
+    imports.push_resolver("env", &RuntimeModuleImportResolver);
 
-	let instance = ModuleInstance::new(&module, &imports)?
-		.assert_no_start();
+    let instance = ModuleInstance::new(&module, &imports)?.assert_no_start();
 
-	Ok(instance)
+    Ok(instance)
 }
 
 fn play(
-	x_instance: ModuleRef,
-	o_instance: ModuleRef,
-	game: &mut tictactoe::Game,
+    x_instance: ModuleRef,
+    o_instance: ModuleRef,
+    game: &mut tictactoe::Game,
 ) -> Result<tictactoe::GameResult, Error> {
-	let mut turn_of = tictactoe::Player::X;
-	let game_result = loop {
-		let (instance, next_turn_of) = match turn_of {
-			tictactoe::Player::X => (&x_instance, tictactoe::Player::O),
-			tictactoe::Player::O => (&o_instance, tictactoe::Player::X),
-		};
+    let mut turn_of = tictactoe::Player::X;
+    let game_result = loop {
+        let (instance, next_turn_of) = match turn_of {
+            tictactoe::Player::X => (&x_instance, tictactoe::Player::O),
+            tictactoe::Player::O => (&o_instance, tictactoe::Player::X),
+        };
 
-		{
-			let mut runtime = Runtime {
-				player: turn_of,
-				game: game,
-			};
-			let _ = instance.invoke_export("mk_turn", &[], &mut runtime)?;
-		}
+        {
+            let mut runtime = Runtime {
+                player: turn_of,
+                game: game,
+            };
+            let _ = instance.invoke_export("mk_turn", &[], &mut runtime)?;
+        }
 
-		match game.game_result() {
-			Some(game_result) => break game_result,
-			None => {}
-		}
+        match game.game_result() {
+            Some(game_result) => break game_result,
+            None => {}
+        }
 
-		turn_of = next_turn_of;
-	};
+        turn_of = next_turn_of;
+    };
 
-	Ok(game_result)
+    Ok(game_result)
 }
 
 fn main() {
-	let mut game = tictactoe::Game::new();
+    let mut game = tictactoe::Game::new();
 
-	let args: Vec<_> = env::args().collect();
-	if args.len() < 3 {
-		println!("Usage: {} <x player module> <y player module>", args[0]);
-		return;
-	}
+    let args: Vec<_> = env::args().collect();
+    if args.len() < 3 {
+        println!("Usage: {} <x player module> <y player module>", args[0]);
+        return;
+    }
 
-	// Instantiate modules of X and O players.
-	let x_instance = instantiate(&args[1]).expect("X player module to load");
-	let o_instance = instantiate(&args[2]).expect("Y player module to load");
+    // Instantiate modules of X and O players.
+    let x_instance = instantiate(&args[1]).expect("X player module to load");
+    let o_instance = instantiate(&args[2]).expect("Y player module to load");
 
-	let result = play(x_instance, o_instance, &mut game);
-	println!("result = {:?}, game = {:#?}", result, game);
+    let result = play(x_instance, o_instance, &mut game);
+    println!("result = {:?}, game = {:#?}", result, game);
 }

fuzz/Cargo.toml

@@ -10,11 +10,13 @@ cargo-fuzz = true
 
 [dependencies]
 wasmi = { path = ".." }
-wabt = "0.2.0"
+wabt = "0.9"
 wasmparser = "0.14.1"
+tempdir = "0.3.6"
 
 [dependencies.libfuzzer-sys]
 git = "https://github.com/rust-fuzz/libfuzzer-sys.git"
+rev = "737524f7de1e85342b8b6cd1c01edc71018183ba"
 
 # Prevent this from interfering with workspaces
 [workspace]
@@ -31,3 +33,7 @@ path = "fuzz_targets/load_wabt.rs"
 [[bin]]
 name = "load_wasmparser"
 path = "fuzz_targets/load_wasmparser.rs"
+
+[[bin]]
+name = "load_spec"
+path = "fuzz_targets/load_spec.rs"

fuzz/fuzz_targets/load_spec.rs

@@ -0,0 +1,53 @@
+#![no_main]
+#[macro_use]
+extern crate libfuzzer_sys;
+extern crate wabt;
+extern crate wasmi;
+extern crate tempdir;
+
+use std::fs::File;
+use std::io::Write;
+use std::process::{Command, Stdio};
+
+fn run_spec(data: &[u8]) -> Result<(), ()> {
+	let temp_dir = tempdir::TempDir::new("spec").unwrap();
+	let mut seed_path = temp_dir.path().to_path_buf();
+	seed_path.push("test.wasm");
+
+	{
+		let mut seedfile =
+			File::create(&seed_path).expect("open temporary file for writing to store fuzzer input");
+		seedfile.write_all(data).expect(
+			"write fuzzer input to temporary file",
+		);
+		seedfile.flush().expect(
+			"flush fuzzer input to temporary file before starting wasm-opt",
+		);
+	}
+
+	let exit_status = Command::new("wasm")
+		.arg("-d")
+		.arg(&seed_path)
+		.stdout(Stdio::null())
+		.stderr(Stdio::null())
+		.status()
+		.expect("failed to execute `wasm`");
+
+	if exit_status.success() {
+		Ok(())
+	} else {
+		Err(())
+	}
+}
+
+fn run_wasmi(data: &[u8]) -> Result<(), ()> {
+	let _ = wasmi::Module::from_buffer(data).map_err(|_| ())?;
+	Ok(())
+}
+
+fuzz_target!(|data: &[u8]| {
+	let wasmi_result = run_wasmi(data);
+	let wasm_result = run_spec(data);
+
+	assert_eq!(wasmi_result.is_ok(), wasm_result.is_ok());
+});

hfuzz/.gitignore

@@ -0,0 +1,2 @@
+hfuzz_workspace/
+hfuzz_target/

hfuzz/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "hfuzz"
+version = "0.1.0"
+authors = ["Sergey Pepyakin <s.pepyakin@gmail.com>"]
+
+[dependencies]
+honggfuzz = "=0.5.9" # Strict equal since hfuzz requires dep and cmd versions to match.
+wasmi = { path = ".." }
+tempdir = "0.3.6"
+wabt = "0.9"

hfuzz/src/main.rs

@@ -0,0 +1,70 @@
+#[macro_use] extern crate honggfuzz;
+
+extern crate wabt;
+extern crate wasmi;
+extern crate tempdir;
+
+use std::fs::File;
+use std::io::Write;
+use std::process::{Command, Stdio};
+
+fn dump_all_into_buf(src: &[u8], buf: &mut [u8; 64]) {
+	let common_len = usize::min(src.len(), buf.len());
+	buf[0..common_len].copy_from_slice(&src[0..common_len]);
+}
+
+fn run_spec(data: &[u8], stdout_msg_buf: &mut [u8; 64], stderr_msg_buf: &mut [u8; 64]) -> Result<(), ()> {
+	let temp_dir = tempdir::TempDir::new("spec").unwrap();
+	let mut seed_path = temp_dir.path().to_path_buf();
+	seed_path.push("test.wasm");
+
+	{
+		let mut seedfile =
+			File::create(&seed_path).expect("open temporary file for writing to store fuzzer input");
+		seedfile.write_all(data).expect(
+			"write fuzzer input to temporary file",
+		);
+		seedfile.flush().expect(
+			"flush fuzzer input to temporary file before starting wasm-opt",
+		);
+	}
+
+	let output = Command::new("wasm")
+		.arg("-d")
+		.arg(&seed_path)
+		.stdout(Stdio::null())
+		.stderr(Stdio::null())
+		.output()
+		.expect("failed to execute `wasm`");
+
+	if output.status.success() {
+		Ok(())
+	} else {
+		dump_all_into_buf(&output.stdout, stdout_msg_buf);
+		dump_all_into_buf(&output.stderr, stderr_msg_buf);
+		Err(())
+	}
+}
+
+fn run_wasmi(data: &[u8]) -> Result<(), ()> {
+	let _ = wasmi::Module::from_buffer(data).map_err(|_| ())?;
+	Ok(())
+}
+
+fn main() {
+	loop {
+		fuzz!(|data: &[u8]| {
+			// Keep messages on stack. This should lead to a different stack hashes for
+			// different error messages.
+			let mut stdout_msg_buf: [u8; 64] = [0; 64];
+			let mut stderr_msg_buf: [u8; 64] = [0; 64];
+
+			let wasmi_result = run_wasmi(data);
+			let wasm_result = run_spec(data, &mut stdout_msg_buf, &mut stderr_msg_buf);
+
+			if wasmi_result.is_ok() != wasm_result.is_ok() {
+				panic!("stdout: {:?}, stderr: {:?}", &stdout_msg_buf[..], &stderr_msg_buf as &[u8]);
+			}
+		});
+	}
+}

hfuzz/test.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+
+export HFUZZ_RUN_ARGS="--max_file_size 2048"
+
+die() { echo "$*"; exit 1; }
+
+command -v wasm || die "spec interpreter 'wasm' is not on PATH";
+
+rustup run nightly cargo hfuzz run hfuzz

src/bin/instantiate.rs

@@ -5,77 +5,79 @@ extern crate wasmi;
 
 use std::env::args;
 use std::fs::File;
-use wasmi::{
-	Error, FuncInstance, FuncRef, GlobalDescriptor, GlobalInstance, GlobalRef,
-	ImportsBuilder, MemoryDescriptor, MemoryInstance, MemoryRef, Module,
-	ModuleImportResolver, ModuleInstance, NopExternals, RuntimeValue, Signature,
-	TableDescriptor, TableInstance, TableRef};
 use wasmi::memory_units::*;
+use wasmi::{
+    Error, FuncInstance, FuncRef, GlobalDescriptor, GlobalInstance, GlobalRef, ImportsBuilder,
+    MemoryDescriptor, MemoryInstance, MemoryRef, Module, ModuleImportResolver, ModuleInstance,
+    NopExternals, RuntimeValue, Signature, TableDescriptor, TableInstance, TableRef,
+};
 
 fn load_from_file(filename: &str) -> Module {
-	use std::io::prelude::*;
-	let mut file = File::open(filename).unwrap();
-	let mut buf = Vec::new();
-	file.read_to_end(&mut buf).unwrap();
-	Module::from_buffer(buf).unwrap()
+    use std::io::prelude::*;
+    let mut file = File::open(filename).unwrap();
+    let mut buf = Vec::new();
+    file.read_to_end(&mut buf).unwrap();
+    Module::from_buffer(buf).unwrap()
 }
 
 struct ResolveAll;
 
 impl ModuleImportResolver for ResolveAll {
-	fn resolve_func(&self, _field_name: &str, signature: &Signature) -> Result<FuncRef, Error> {
-		Ok(FuncInstance::alloc_host(signature.clone(), 0))
-	}
+    fn resolve_func(&self, _field_name: &str, signature: &Signature) -> Result<FuncRef, Error> {
+        Ok(FuncInstance::alloc_host(signature.clone(), 0))
+    }
 
-	fn resolve_global(
-		&self,
-		_field_name: &str,
-		global_type: &GlobalDescriptor,
-	) -> Result<GlobalRef, Error> {
-		Ok(GlobalInstance::alloc(
-			RuntimeValue::default(global_type.value_type()),
-			global_type.is_mutable(),
-		))
-	}
+    fn resolve_global(
+        &self,
+        _field_name: &str,
+        global_type: &GlobalDescriptor,
+    ) -> Result<GlobalRef, Error> {
+        Ok(GlobalInstance::alloc(
+            RuntimeValue::default(global_type.value_type()),
+            global_type.is_mutable(),
+        ))
+    }
 
-	fn resolve_memory(
-		&self,
-		_field_name: &str,
-		memory_type: &MemoryDescriptor,
-	) -> Result<MemoryRef, Error> {
-		Ok(MemoryInstance::alloc(
-			Pages(memory_type.initial() as usize),
-			memory_type.maximum().map(|m| Pages(m as usize)),
-		).unwrap())
-	}
+    fn resolve_memory(
+        &self,
+        _field_name: &str,
+        memory_type: &MemoryDescriptor,
+    ) -> Result<MemoryRef, Error> {
+        Ok(MemoryInstance::alloc(
+            Pages(memory_type.initial() as usize),
+            memory_type.maximum().map(|m| Pages(m as usize)),
+        )
+        .unwrap())
+    }
 
-	fn resolve_table(
-		&self,
-		_field_name: &str,
-		table_type: &TableDescriptor,
-	) -> Result<TableRef, Error> {
-		Ok(TableInstance::alloc(table_type.initial(), table_type.maximum()).unwrap())
-	}
+    fn resolve_table(
+        &self,
+        _field_name: &str,
+        table_type: &TableDescriptor,
+    ) -> Result<TableRef, Error> {
+        Ok(TableInstance::alloc(table_type.initial(), table_type.maximum()).unwrap())
+    }
 }
 
 fn main() {
-	let args: Vec<_> = args().collect();
-	if args.len() != 2 {
-		println!("Usage: {} <wasm file>", args[0]);
-		return;
-	}
-	let module = load_from_file(&args[1]);
-	let _ = ModuleInstance::new(
-		&module,
-		&ImportsBuilder::default()
-			// Well known imports.
-			.with_resolver("env", &ResolveAll)
-			.with_resolver("global", &ResolveAll)
-			.with_resolver("foo", &ResolveAll)
-			.with_resolver("global.Math", &ResolveAll)
-			.with_resolver("asm2wasm", &ResolveAll)
-			.with_resolver("spectest", &ResolveAll),
-	).expect("Failed to instantiate module")
-		.run_start(&mut NopExternals)
-		.expect("Failed to run start function in module");
+    let args: Vec<_> = args().collect();
+    if args.len() != 2 {
+        println!("Usage: {} <wasm file>", args[0]);
+        return;
+    }
+    let module = load_from_file(&args[1]);
+    let _ = ModuleInstance::new(
+        &module,
+        &ImportsBuilder::default()
+            // Well known imports.
+            .with_resolver("env", &ResolveAll)
+            .with_resolver("global", &ResolveAll)
+            .with_resolver("foo", &ResolveAll)
+            .with_resolver("global.Math", &ResolveAll)
+            .with_resolver("asm2wasm", &ResolveAll)
+            .with_resolver("spectest", &ResolveAll),
+    )
+    .expect("Failed to instantiate module")
+    .run_start(&mut NopExternals)
+    .expect("Failed to run start function in module");
 }

src/common/mod.rs

@@ -1,44 +0,0 @@
-use parity_wasm::elements::BlockType;
-
-pub mod stack;
-
-/// Index of default linear memory.
-pub const DEFAULT_MEMORY_INDEX: u32 = 0;
-/// Index of default table.
-pub const DEFAULT_TABLE_INDEX: u32 = 0;
-
-/// Control stack frame.
-#[derive(Debug, Clone)]
-pub struct BlockFrame {
-	/// Frame type.
-	pub frame_type: BlockFrameType,
-	/// A signature, which is a block signature type indicating the number and types of result values of the region.
-	pub block_type: BlockType,
-	/// A label for reference to block instruction.
-	pub begin_position: usize,
-	/// A label for reference from branch instructions.
-	pub branch_position: usize,
-	/// A label for reference from end instructions.
-	pub end_position: usize,
-	/// A limit integer value, which is an index into the value stack indicating where to reset it to on a branch to that label.
-	pub value_stack_len: usize,
-	/// Boolean which signals whether value stack became polymorphic. Value stack starts in non-polymorphic state and
-	/// becomes polymorphic only after an instruction that never passes control further is executed,
-	/// i.e. `unreachable`, `br` (but not `br_if`!), etc.
-	pub polymorphic_stack: bool,
-}
-
-/// Type of block frame.
-#[derive(Debug, Clone, Copy, PartialEq)]
-pub enum BlockFrameType {
-	/// Function frame.
-	Function,
-	/// Usual block frame.
-	Block,
-	/// Loop frame (branching to the beginning of block).
-	Loop,
-	/// True-subblock of if expression.
-	IfTrue,
-	/// False-subblock of if expression.
-	IfFalse,
-}

src/common/stack.rs

@@ -1,89 +0,0 @@
-
-use std::collections::VecDeque;
-use std::error;
-use std::fmt;
-
-#[derive(Debug)]
-pub struct Error(String);
-
-impl fmt::Display for Error {
-	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-		write!(f, "{}", self.0)
-	}
-}
-
-impl error::Error for Error {
-	fn description(&self) -> &str {
-		&self.0
-	}
-}
-
-/// Stack with limit.
-#[derive(Debug)]
-pub struct StackWithLimit<T> where T: Clone {
-	/// Stack values.
-	values: VecDeque<T>,
-	/// Stack limit (maximal stack len).
-	limit: usize,
-}
-
-impl<T> StackWithLimit<T> where T: Clone {
-	pub fn with_limit(limit: usize) -> Self {
-		StackWithLimit {
-			values: VecDeque::new(),
-			limit: limit
-		}
-	}
-
-	pub fn is_empty(&self) -> bool {
-		self.values.is_empty()
-	}
-
-	pub fn len(&self) -> usize {
-		self.values.len()
-	}
-
-	pub fn limit(&self) -> usize {
-		self.limit
-	}
-
-	pub fn top(&self) -> Result<&T, Error> {
-		self.values
-			.back()
-			.ok_or_else(|| Error("non-empty stack expected".into()))
-	}
-
-	pub fn top_mut(&mut self) -> Result<&mut T, Error> {
-		self.values
-			.back_mut()
-			.ok_or_else(|| Error("non-empty stack expected".into()))
-	}
-
-	pub fn get(&self, index: usize) -> Result<&T, Error> {
-		if index >= self.values.len() {
-			return Err(Error(format!("trying to get value at position {} on stack of size {}", index, self.values.len())));
-		}
-
-		Ok(self.values.get(self.values.len() - 1 - index).expect("checked couple of lines above"))
-	}
-
-	pub fn push(&mut self, value: T) -> Result<(), Error> {
-		if self.values.len() >= self.limit {
-			return Err(Error(format!("exceeded stack limit {}", self.limit)));
-		}
-
-		self.values.push_back(value);
-		Ok(())
-	}
-
-	pub fn pop(&mut self) -> Result<T, Error> {
-		self.values
-			.pop_back()
-			.ok_or_else(|| Error("non-empty stack expected".into()))
-	}
-
-	pub fn resize(&mut self, new_size: usize, dummy: T) {
-		debug_assert!(new_size <= self.values.len());
-		self.values.resize(new_size, dummy);
-	}
-}

src/func.rs

@@ -1,12 +1,17 @@
-use std::rc::{Rc, Weak};
-use std::fmt;
-use std::collections::HashMap;
-use parity_wasm::elements::{Local, Opcodes};
-use {Trap, TrapKind, Signature};
+use alloc::{
+    borrow::Cow,
+    rc::{Rc, Weak},
+    vec::Vec,
+};
+use core::fmt;
 use host::Externals;
-use runner::{check_function_args, Interpreter};
-use value::RuntimeValue;
+use isa;
 use module::ModuleInstance;
+use parity_wasm::elements::Local;
+use runner::{check_function_args, Interpreter, InterpreterState, StackRecycler};
+use types::ValueType;
+use value::RuntimeValue;
+use {Signature, Trap};
 
 /// Reference to a function (See [`FuncInstance`] for details).
 ///
@@ -16,16 +21,16 @@ use module::ModuleInstance;
 #[derive(Clone, Debug)]
 pub struct FuncRef(Rc<FuncInstance>);
 
-impl ::std::ops::Deref for FuncRef {
-	type Target = FuncInstance;
-	fn deref(&self) -> &FuncInstance {
-		&self.0
-	}
+impl ::core::ops::Deref for FuncRef {
+    type Target = FuncInstance;
+    fn deref(&self) -> &FuncInstance {
+        &self.0
+    }
 }
 
 /// Runtime representation of a function.
 ///
-/// Functions are the unit of orgianization of code in WebAssembly. Each function takes a sequence of values
+/// Functions are the unit of organization of code in WebAssembly. Each function takes a sequence of values
 /// as parameters and either optionally return a value or trap.
 /// Functions can call other function including itself (i.e recursive calls are allowed) and imported functions
 /// (i.e functions defined in another module or by the host environment).
@@ -41,123 +46,307 @@ pub struct FuncInstance(FuncInstanceInternal);
 
 #[derive(Clone)]
 pub(crate) enum FuncInstanceInternal {
-	Internal {
-		signature: Rc<Signature>,
-		module: Weak<ModuleInstance>,
-		body: Rc<FuncBody>,
-	},
-	Host {
-		signature: Signature,
-		host_func_index: usize,
-	},
+    Internal {
+        signature: Rc<Signature>,
+        module: Weak<ModuleInstance>,
+        body: Rc<FuncBody>,
+    },
+    Host {
+        signature: Signature,
+        host_func_index: usize,
+    },
 }
 
 impl fmt::Debug for FuncInstance {
-	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-		match self.as_internal() {
-			&FuncInstanceInternal::Internal {
-				ref signature,
-				..
-			} => {
-				// We can't write description of self.module here, because it generate
-				// debug string for function instances and this will lead to infinite loop.
-				write!(
-					f,
-					"Internal {{ signature={:?} }}",
-					signature,
-				)
-			}
-			&FuncInstanceInternal::Host { ref signature, .. } => {
-				write!(f, "Host {{ signature={:?} }}", signature)
-			}
-		}
-	}
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self.as_internal() {
+            &FuncInstanceInternal::Internal { ref signature, .. } => {
+                // We can't write description of self.module here, because it generate
+                // debug string for function instances and this will lead to infinite loop.
+                write!(f, "Internal {{ signature={:?} }}", signature,)
+            }
+            &FuncInstanceInternal::Host { ref signature, .. } => {
+                write!(f, "Host {{ signature={:?} }}", signature)
+            }
+        }
+    }
 }
 
 impl FuncInstance {
-	/// Allocate a function instance for a host function.
-	///
-	/// When this function instance will be called by the wasm code,
-	/// the instance of [`Externals`] will be invoked by calling `invoke_index`
-	/// with specified `host_func_index` here.
-	/// This call will be made with the `signature` provided here.
-	///
-	/// [`Externals`]: trait.Externals.html
-	pub fn alloc_host(signature: Signature, host_func_index: usize) -> FuncRef {
-		let func = FuncInstanceInternal::Host {
-			signature,
-			host_func_index,
-		};
-		FuncRef(Rc::new(FuncInstance(func)))
-	}
+    /// Allocate a function instance for a host function.
+    ///
+    /// When this function instance will be called by the wasm code,
+    /// the instance of [`Externals`] will be invoked by calling `invoke_index`
+    /// with specified `host_func_index` here.
+    /// This call will be made with the `signature` provided here.
+    ///
+    /// [`Externals`]: trait.Externals.html
+    pub fn alloc_host(signature: Signature, host_func_index: usize) -> FuncRef {
+        let func = FuncInstanceInternal::Host {
+            signature,
+            host_func_index,
+        };
+        FuncRef(Rc::new(FuncInstance(func)))
+    }
 
-	/// Returns [signature] of this function instance.
-	///
-	/// This function instance can only be called with matching signatures.
-	///
-	/// [signature]: struct.Signature.html
-	pub fn signature(&self) -> &Signature {
-		match *self.as_internal() {
-			FuncInstanceInternal::Internal { ref signature, .. } => signature,
-			FuncInstanceInternal::Host { ref signature, .. } => signature,
-		}
-	}
+    /// Returns [signature] of this function instance.
+    ///
+    /// This function instance can only be called with matching signatures.
+    ///
+    /// [signature]: struct.Signature.html
+    pub fn signature(&self) -> &Signature {
+        match *self.as_internal() {
+            FuncInstanceInternal::Internal { ref signature, .. } => signature,
+            FuncInstanceInternal::Host { ref signature, .. } => signature,
+        }
+    }
 
-	pub(crate) fn as_internal(&self) -> &FuncInstanceInternal {
-		&self.0
-	}
+    pub(crate) fn as_internal(&self) -> &FuncInstanceInternal {
+        &self.0
+    }
 
-	pub(crate) fn alloc_internal(
-		module: Weak<ModuleInstance>,
-		signature: Rc<Signature>,
-		body: FuncBody,
-	) -> FuncRef {
-		let func = FuncInstanceInternal::Internal {
-			signature,
-			module: module,
-			body: Rc::new(body),
-		};
-		FuncRef(Rc::new(FuncInstance(func)))
-	}
+    pub(crate) fn alloc_internal(
+        module: Weak<ModuleInstance>,
+        signature: Rc<Signature>,
+        body: FuncBody,
+    ) -> FuncRef {
+        let func = FuncInstanceInternal::Internal {
+            signature,
+            module: module,
+            body: Rc::new(body),
+        };
+        FuncRef(Rc::new(FuncInstance(func)))
+    }
 
-	pub(crate) fn body(&self) -> Option<Rc<FuncBody>> {
-		match *self.as_internal() {
-			FuncInstanceInternal::Internal { ref body, .. } => Some(Rc::clone(body)),
-			FuncInstanceInternal::Host { .. } => None,
-		}
-	}
+    pub(crate) fn body(&self) -> Option<Rc<FuncBody>> {
+        match *self.as_internal() {
+            FuncInstanceInternal::Internal { ref body, .. } => Some(Rc::clone(body)),
+            FuncInstanceInternal::Host { .. } => None,
+        }
+    }
 
-	/// Invoke this function.
-	///
-	/// # Errors
-	///
-	/// Returns `Err` if `args` types is not match function [`signature`] or
-	/// if [`Trap`] at execution time occured.
-	///
-	/// [`signature`]: #method.signature
-	/// [`Trap`]: #enum.Trap.html
-	pub fn invoke<E: Externals>(
-		func: &FuncRef,
-		args: &[RuntimeValue],
-		externals: &mut E,
-	) -> Result<Option<RuntimeValue>, Trap> {
-		check_function_args(func.signature(), &args).map_err(|_| TrapKind::UnexpectedSignature)?;
-		match *func.as_internal() {
-			FuncInstanceInternal::Internal { .. } => {
-				let mut interpreter = Interpreter::new(externals);
-				interpreter.start_execution(func, args)
-			}
-			FuncInstanceInternal::Host {
-				ref host_func_index,
-				..
-			} => externals.invoke_index(*host_func_index, args.into()),
-		}
-	}
+    /// Invoke this function.
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if `args` types is not match function [`signature`] or
+    /// if [`Trap`] at execution time occured.
+    ///
+    /// [`signature`]: #method.signature
+    /// [`Trap`]: #enum.Trap.html
+    pub fn invoke<E: Externals>(
+        func: &FuncRef,
+        args: &[RuntimeValue],
+        externals: &mut E,
+    ) -> Result<Option<RuntimeValue>, Trap> {
+        check_function_args(func.signature(), &args)?;
+        match *func.as_internal() {
+            FuncInstanceInternal::Internal { .. } => {
+                let mut interpreter = Interpreter::new(func, args, None)?;
+                interpreter.start_execution(externals)
+            }
+            FuncInstanceInternal::Host {
+                ref host_func_index,
+                ..
+            } => externals.invoke_index(*host_func_index, args.into()),
+        }
+    }
+
+    /// Invoke this function using recycled stacks.
+    ///
+    /// # Errors
+    ///
+    /// Same as [`invoke`].
+    ///
+    /// [`invoke`]: #method.invoke
+    pub fn invoke_with_stack<E: Externals>(
+        func: &FuncRef,
+        args: &[RuntimeValue],
+        externals: &mut E,
+        stack_recycler: &mut StackRecycler,
+    ) -> Result<Option<RuntimeValue>, Trap> {
+        check_function_args(func.signature(), &args)?;
+        match *func.as_internal() {
+            FuncInstanceInternal::Internal { .. } => {
+                let mut interpreter = Interpreter::new(func, args, Some(stack_recycler))?;
+                let return_value = interpreter.start_execution(externals);
+                stack_recycler.recycle(interpreter);
+                return_value
+            }
+            FuncInstanceInternal::Host {
+                ref host_func_index,
+                ..
+            } => externals.invoke_index(*host_func_index, args.into()),
+        }
+    }
+
+    /// Invoke the function, get a resumable handle. This handle can then be used to [`start_execution`]. If a
+    /// Host trap happens, caller can use [`resume_execution`] to feed the expected return value back in, and then
+    /// continue the execution.
+    ///
+    /// This is an experimental API, and this functionality may not be available in other WebAssembly engines.
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if `args` types is not match function [`signature`].
+    ///
+    /// [`signature`]: #method.signature
+    /// [`Trap`]: #enum.Trap.html
+    /// [`start_execution`]: struct.FuncInvocation.html#method.start_execution
+    /// [`resume_execution`]: struct.FuncInvocation.html#method.resume_execution
+    pub fn invoke_resumable<'args>(
+        func: &FuncRef,
+        args: impl Into<Cow<'args, [RuntimeValue]>>,
+    ) -> Result<FuncInvocation<'args>, Trap> {
+        let args = args.into();
+        check_function_args(func.signature(), &args)?;
+        match *func.as_internal() {
+            FuncInstanceInternal::Internal { .. } => {
+                let interpreter = Interpreter::new(func, &*args, None)?;
+                Ok(FuncInvocation {
+                    kind: FuncInvocationKind::Internal(interpreter),
+                })
+            }
+            FuncInstanceInternal::Host {
+                ref host_func_index,
+                ..
+            } => Ok(FuncInvocation {
+                kind: FuncInvocationKind::Host {
+                    args,
+                    host_func_index: *host_func_index,
+                    finished: false,
+                },
+            }),
+        }
+    }
+}
+
+/// A resumable invocation error.
+#[derive(Debug)]
+pub enum ResumableError {
+    /// Trap happened.
+    Trap(Trap),
+    /// The invocation is not resumable.
+    ///
+    /// Invocations are only resumable if a host function is called, and the host function returns a trap of `Host` kind. For other cases, this error will be returned. This includes:
+    /// - The invocation is directly a host function.
+    /// - The invocation has not been started.
+    /// - The invocation returns normally or returns any trap other than `Host` kind.
+    ///
+    /// This error is returned by [`resume_execution`].
+    ///
+    /// [`resume_execution`]: struct.FuncInvocation.html#method.resume_execution
+    NotResumable,
+    /// The invocation has already been started.
+    ///
+    /// This error is returned by [`start_execution`].
+    ///
+    /// [`start_execution`]: struct.FuncInvocation.html#method.start_execution
+    AlreadyStarted,
+}
+
+impl From<Trap> for ResumableError {
+    fn from(trap: Trap) -> Self {
+        ResumableError::Trap(trap)
+    }
+}
+
+/// A resumable invocation handle. This struct is returned by `FuncInstance::invoke_resumable`.
+pub struct FuncInvocation<'args> {
+    kind: FuncInvocationKind<'args>,
+}
+
+enum FuncInvocationKind<'args> {
+    Internal(Interpreter),
+    Host {
+        args: Cow<'args, [RuntimeValue]>,
+        host_func_index: usize,
+        finished: bool,
+    },
+}
+
+impl<'args> FuncInvocation<'args> {
+    /// Whether this invocation is currently resumable.
+    pub fn is_resumable(&self) -> bool {
+        match &self.kind {
+            &FuncInvocationKind::Internal(ref interpreter) => interpreter.state().is_resumable(),
+            &FuncInvocationKind::Host { .. } => false,
+        }
+    }
+
+    /// If the invocation is resumable, the expected return value type to be feed back in.
+    pub fn resumable_value_type(&self) -> Option<ValueType> {
+        match &self.kind {
+            &FuncInvocationKind::Internal(ref interpreter) => match interpreter.state() {
+                &InterpreterState::Resumable(ref value_type) => value_type.clone(),
+                _ => None,
+            },
+            &FuncInvocationKind::Host { .. } => None,
+        }
+    }
+
+    /// Start the invocation execution.
+    pub fn start_execution<'externals, E: Externals + 'externals>(
+        &mut self,
+        externals: &'externals mut E,
+    ) -> Result<Option<RuntimeValue>, ResumableError> {
+        match self.kind {
+            FuncInvocationKind::Internal(ref mut interpreter) => {
+                if interpreter.state() != &InterpreterState::Initialized {
+                    return Err(ResumableError::AlreadyStarted);
+                }
+                Ok(interpreter.start_execution(externals)?)
+            }
+            FuncInvocationKind::Host {
+                ref args,
+                ref mut finished,
+                ref host_func_index,
+            } => {
+                if *finished {
+                    return Err(ResumableError::AlreadyStarted);
+                }
+                *finished = true;
+                Ok(externals.invoke_index(*host_func_index, args.as_ref().into())?)
+            }
+        }
+    }
+
+    /// Resume an execution if a previous trap of Host kind happened.
+    ///
+    /// `return_val` must be of the value type [`resumable_value_type`], defined by the host function import. Otherwise,
+    /// `UnexpectedSignature` trap will be returned. The current invocation must also be resumable
+    /// [`is_resumable`]. Otherwise, a `NotResumable` error will be returned.
+    ///
+    /// [`resumable_value_type`]: #method.resumable_value_type
+    /// [`is_resumable`]: #method.is_resumable
+    pub fn resume_execution<'externals, E: Externals + 'externals>(
+        &mut self,
+        return_val: Option<RuntimeValue>,
+        externals: &'externals mut E,
+    ) -> Result<Option<RuntimeValue>, ResumableError> {
+        use crate::TrapKind;
+
+        if return_val.map(|v| v.value_type()) != self.resumable_value_type() {
+            return Err(ResumableError::Trap(Trap::new(
+                TrapKind::UnexpectedSignature,
+            )));
+        }
+
+        match &mut self.kind {
+            FuncInvocationKind::Internal(interpreter) => {
+                if interpreter.state().is_resumable() {
+                    Ok(interpreter.resume_execution(return_val, externals)?)
+                } else {
+                    Err(ResumableError::AlreadyStarted)
+                }
+            }
+            FuncInvocationKind::Host { .. } => Err(ResumableError::NotResumable),
+        }
+    }
 }
 
 #[derive(Clone, Debug)]
 pub struct FuncBody {
-	pub locals: Vec<Local>,
-	pub opcodes: Opcodes,
-	pub labels: HashMap<usize, usize>,
+    pub locals: Vec<Local>,
+    pub code: isa::Instructions,
 }

src/global.rs

@@ -1,9 +1,9 @@
-use std::rc::Rc;
-use std::cell::Cell;
+use alloc::rc::Rc;
+use core::cell::Cell;
+use parity_wasm::elements::ValueType as EValueType;
+use types::ValueType;
 use value::RuntimeValue;
 use Error;
-use types::ValueType;
-use parity_wasm::elements::{ValueType as EValueType};
 
 /// Reference to a global variable (See [`GlobalInstance`] for details).
 ///
@@ -13,11 +13,11 @@ use parity_wasm::elements::{ValueType as EValueType};
 #[derive(Clone, Debug)]
 pub struct GlobalRef(Rc<GlobalInstance>);
 
-impl ::std::ops::Deref for GlobalRef {
-	type Target = GlobalInstance;
-	fn deref(&self) -> &GlobalInstance {
-		&self.0
-	}
+impl ::core::ops::Deref for GlobalRef {
+    type Target = GlobalInstance;
+    fn deref(&self) -> &GlobalInstance {
+        &self.0
+    }
 }
 
 /// Runtime representation of a global variable (or `global` for short).
@@ -33,57 +33,59 @@ impl ::std::ops::Deref for GlobalRef {
 /// [`I64`]: enum.RuntimeValue.html#variant.I64
 #[derive(Debug)]
 pub struct GlobalInstance {
-	val: Cell<RuntimeValue>,
-	mutable: bool,
+    val: Cell<RuntimeValue>,
+    mutable: bool,
 }
 
 impl GlobalInstance {
-	/// Allocate a global variable instance.
-	///
-	/// Since it is possible to export only immutable globals,
-	/// users likely want to set `mutable` to `false`.
-	pub fn alloc(val: RuntimeValue, mutable: bool) -> GlobalRef {
-		GlobalRef(Rc::new(GlobalInstance {
-			val: Cell::new(val),
-			mutable,
-		}))
-	}
+    /// Allocate a global variable instance.
+    ///
+    /// Since it is possible to export only immutable globals,
+    /// users likely want to set `mutable` to `false`.
+    pub fn alloc(val: RuntimeValue, mutable: bool) -> GlobalRef {
+        GlobalRef(Rc::new(GlobalInstance {
+            val: Cell::new(val),
+            mutable,
+        }))
+    }
 
-	/// Change the value of this global variable.
-	///
-	/// # Errors
-	///
-	/// Returns `Err` if this global isn't mutable or if
-	/// type of `val` doesn't match global's type.
-	pub fn set(&self, val: RuntimeValue) -> Result<(), Error> {
-		if !self.mutable {
-			return Err(Error::Global("Attempt to change an immutable variable".into()));
-		}
-		if self.value_type() != val.value_type() {
-			return Err(Error::Global("Attempt to change variable type".into()));
-		}
-		self.val.set(val);
-		Ok(())
-	}
+    /// Change the value of this global variable.
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if this global isn't mutable or if
+    /// type of `val` doesn't match global's type.
+    pub fn set(&self, val: RuntimeValue) -> Result<(), Error> {
+        if !self.mutable {
+            return Err(Error::Global(
+                "Attempt to change an immutable variable".into(),
+            ));
+        }
+        if self.value_type() != val.value_type() {
+            return Err(Error::Global("Attempt to change variable type".into()));
+        }
+        self.val.set(val);
+        Ok(())
+    }
 
-	/// Get the value of this global variable.
-	pub fn get(&self) -> RuntimeValue {
-		self.val.get()
-	}
+    /// Get the value of this global variable.
+    pub fn get(&self) -> RuntimeValue {
+        self.val.get()
+    }
 
-	/// Returns if this global variable is mutable.
-	///
-	/// Note: Imported and/or exported globals are always immutable.
-	pub fn is_mutable(&self) -> bool {
-		self.mutable
-	}
+    /// Returns if this global variable is mutable.
+    ///
+    /// Note: Imported and/or exported globals are always immutable.
+    pub fn is_mutable(&self) -> bool {
+        self.mutable
+    }
 
-	/// Returns value type of this global variable.
-	pub fn value_type(&self) -> ValueType {
-		self.val.get().value_type()
-	}
+    /// Returns value type of this global variable.
+    pub fn value_type(&self) -> ValueType {
+        self.val.get().value_type()
+    }
 
-	pub(crate) fn elements_value_type(&self) -> EValueType {
-		self.value_type().into_elements()
-	}
+    pub(crate) fn elements_value_type(&self) -> EValueType {
+        self.value_type().into_elements()
+    }
 }

src/host.rs

@@ -1,6 +1,6 @@
-use std::any::TypeId;
-use value::{RuntimeValue, FromRuntimeValue};
-use {TrapKind, Trap};
+use core::any::TypeId;
+use value::{FromRuntimeValue, RuntimeValue};
+use {Trap, TrapKind};
 
 /// Wrapper around slice of [`RuntimeValue`] for using it
 /// as an argument list conveniently.
@@ -10,55 +10,64 @@ use {TrapKind, Trap};
 pub struct RuntimeArgs<'a>(&'a [RuntimeValue]);
 
 impl<'a> From<&'a [RuntimeValue]> for RuntimeArgs<'a> {
-	fn from(inner: &'a [RuntimeValue]) -> Self {
-		RuntimeArgs(inner)
-	}
+    fn from(inner: &'a [RuntimeValue]) -> Self {
+        RuntimeArgs(inner)
+    }
 }
 
 impl<'a> AsRef<[RuntimeValue]> for RuntimeArgs<'a> {
-	fn as_ref(&self) -> &[RuntimeValue] {
-		self.0
-	}
+    fn as_ref(&self) -> &[RuntimeValue] {
+        self.0
+    }
 }
 
 impl<'a> RuntimeArgs<'a> {
-	/// Extract argument by index `idx`.
-	///
-	/// # Errors
-	///
-	/// Returns `Err` if cast is invalid or not enough arguments.
-	pub fn nth_checked<T>(&self, idx: usize) -> Result<T, Trap> where T: FromRuntimeValue {
-		Ok(self.nth_value_checked(idx)?.try_into().ok_or_else(|| TrapKind::UnexpectedSignature)?)
-	}
+    /// Extract argument by index `idx`.
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if cast is invalid or not enough arguments.
+    pub fn nth_checked<T>(&self, idx: usize) -> Result<T, Trap>
+    where
+        T: FromRuntimeValue,
+    {
+        Ok(self
+            .nth_value_checked(idx)?
+            .try_into()
+            .ok_or_else(|| TrapKind::UnexpectedSignature)?)
+    }
 
-	/// Extract argument as a [`RuntimeValue`] by index `idx`.
-	///
-	/// # Errors
-	///
-	/// Returns `Err` if this list has not enough arguments.
-	///
-	/// [`RuntimeValue`]: enum.RuntimeValue.html
-	pub fn nth_value_checked(&self, idx: usize) -> Result<RuntimeValue, Trap> {
-		if self.0.len() <= idx {
-			return Err(TrapKind::UnexpectedSignature.into());
-		}
-		Ok(self.0[idx])
-	}
+    /// Extract argument as a [`RuntimeValue`] by index `idx`.
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if this list has not enough arguments.
+    ///
+    /// [`RuntimeValue`]: enum.RuntimeValue.html
+    pub fn nth_value_checked(&self, idx: usize) -> Result<RuntimeValue, Trap> {
+        if self.0.len() <= idx {
+            return Err(TrapKind::UnexpectedSignature.into());
+        }
+        Ok(self.0[idx])
+    }
 
-	/// Extract argument by index `idx`.
-	///
-	/// # Panics
-	///
-	/// Panics if cast is invalid or not enough arguments.
-	pub fn nth<T>(&self, idx: usize) -> T where T: FromRuntimeValue {
-		let value = self.nth_value_checked(idx).expect("Invalid argument index");
-		value.try_into().expect("Unexpected argument type")
-	}
+    /// Extract argument by index `idx`.
+    ///
+    /// # Panics
+    ///
+    /// Panics if cast is invalid or not enough arguments.
+    pub fn nth<T>(&self, idx: usize) -> T
+    where
+        T: FromRuntimeValue,
+    {
+        let value = self.nth_value_checked(idx).expect("Invalid argument index");
+        value.try_into().expect("Unexpected argument type")
+    }
 
-	/// Total number of arguments
-	pub fn len(&self) -> usize {
-		self.0.len()
-	}
+    /// Total number of arguments
+    pub fn len(&self) -> usize {
+        self.0.len()
+    }
 }
 
 /// Trait that allows the host to return custom error.
@@ -98,32 +107,32 @@ impl<'a> RuntimeArgs<'a> {
 ///     _ => panic!(),
 /// }
 /// ```
-pub trait HostError: 'static + ::std::fmt::Display + ::std::fmt::Debug + Send + Sync {
-	#[doc(hidden)]
-	fn __private_get_type_id__(&self) -> TypeId {
-		TypeId::of::<Self>()
-	}
+pub trait HostError: 'static + ::core::fmt::Display + ::core::fmt::Debug + Send + Sync {
+    #[doc(hidden)]
+    fn __private_get_type_id__(&self) -> TypeId {
+        TypeId::of::<Self>()
+    }
 }
 
-impl HostError {
-	/// Attempt to downcast this `HostError` to a concrete type by reference.
-	pub fn downcast_ref<T: HostError>(&self) -> Option<&T> {
-		if self.__private_get_type_id__() == TypeId::of::<T>() {
-			unsafe { Some(&*(self as *const HostError as *const T)) }
-		} else {
-			None
-		}
-	}
+impl dyn HostError {
+    /// Attempt to downcast this `HostError` to a concrete type by reference.
+    pub fn downcast_ref<T: HostError>(&self) -> Option<&T> {
+        if self.__private_get_type_id__() == TypeId::of::<T>() {
+            unsafe { Some(&*(self as *const dyn HostError as *const T)) }
+        } else {
+            None
+        }
+    }
 
-	/// Attempt to downcast this `HostError` to a concrete type by mutable
-	/// reference.
-	pub fn downcast_mut<T: HostError>(&mut self) -> Option<&mut T> {
-		if self.__private_get_type_id__() == TypeId::of::<T>() {
-			unsafe { Some(&mut *(self as *mut HostError as *mut T)) }
-		} else {
-			None
-		}
-	}
+    /// Attempt to downcast this `HostError` to a concrete type by mutable
+    /// reference.
+    pub fn downcast_mut<T: HostError>(&mut self) -> Option<&mut T> {
+        if self.__private_get_type_id__() == TypeId::of::<T>() {
+            unsafe { Some(&mut *(self as *mut dyn HostError as *mut T)) }
+        } else {
+            None
+        }
+    }
 }
 
 /// Trait that allows to implement host functions.
@@ -190,20 +199,26 @@ impl HostError {
 ///             }
 ///         };
 ///
+///         if !self.check_signature(index, signature) {
+///             return Err(Error::Instantiation(
+///                 format!("Export {} has a bad signature", field_name)
+///             ));
+///         }
+///
 ///         Ok(FuncInstance::alloc_host(
 ///             Signature::new(&[ValueType::I32, ValueType::I32][..], Some(ValueType::I32)),
-///             ADD_FUNC_INDEX,
+///             index,
 ///         ))
 ///     }
 /// }
 /// ```
 pub trait Externals {
-	/// Perform invoke of a host function by specified `index`.
-	fn invoke_index(
-		&mut self,
-		index: usize,
-		args: RuntimeArgs,
-	) -> Result<Option<RuntimeValue>, Trap>;
+    /// Perform invoke of a host function by specified `index`.
+    fn invoke_index(
+        &mut self,
+        index: usize,
+        args: RuntimeArgs,
+    ) -> Result<Option<RuntimeValue>, Trap>;
 }
 
 /// Implementation of [`Externals`] that just traps on [`invoke_index`].
@@ -213,35 +228,34 @@ pub trait Externals {
 pub struct NopExternals;
 
 impl Externals for NopExternals {
-	fn invoke_index(
-		&mut self,
-		_index: usize,
-		_args: RuntimeArgs,
-	) -> Result<Option<RuntimeValue>, Trap> {
-		Err(TrapKind::Unreachable.into())
-	}
+    fn invoke_index(
+        &mut self,
+        _index: usize,
+        _args: RuntimeArgs,
+    ) -> Result<Option<RuntimeValue>, Trap> {
+        Err(TrapKind::Unreachable.into())
+    }
 }
 
 #[cfg(test)]
 mod tests {
 
-	use value::RuntimeValue;
-	use super::{RuntimeArgs, HostError};
+    use super::{HostError, RuntimeArgs};
+    use value::RuntimeValue;
 
-	#[test]
-	fn i32_runtime_args() {
-		let args: RuntimeArgs = (&[RuntimeValue::I32(0)][..]).into();
-		let val: i32 = args.nth_checked(0).unwrap();
-		assert_eq!(val, 0);
-	}
+    #[test]
+    fn i32_runtime_args() {
+        let args: RuntimeArgs = (&[RuntimeValue::I32(0)][..]).into();
+        let val: i32 = args.nth_checked(0).unwrap();
+        assert_eq!(val, 0);
+    }
 
-	#[test]
-	fn i64_invalid_arg_cast() {
-		let args: RuntimeArgs = (&[RuntimeValue::I64(90534534545322)][..]).into();
-		assert!(args.nth_checked::<i32>(0).is_err());
-	}
+    #[test]
+    fn i64_invalid_arg_cast() {
+        let args: RuntimeArgs = (&[RuntimeValue::I64(90534534545322)][..]).into();
+        assert!(args.nth_checked::<i32>(0).is_err());
+    }
 
-	// Tests that `HostError` trait is object safe.
-	fn _host_error_is_object_safe(_: &HostError) {
-	}
+    // Tests that `HostError` trait is object safe.
+    fn _host_error_is_object_safe(_: &dyn HostError) {}
 }

src/imports.rs

@@ -1,13 +1,13 @@
-use std::collections::HashMap;
+use alloc::{collections::BTreeMap, string::String};
+
+use func::FuncRef;
 use global::GlobalRef;
 use memory::MemoryRef;
-use func::FuncRef;
-use table::TableRef;
 use module::ModuleRef;
-use types::{GlobalDescriptor, TableDescriptor, MemoryDescriptor};
+use table::TableRef;
+use types::{GlobalDescriptor, MemoryDescriptor, TableDescriptor};
 use {Error, Signature};
 
-
 /// Resolver of a module's dependencies.
 ///
 /// A module have dependencies in a form of a list of imports (i.e.
@@ -20,56 +20,55 @@ use {Error, Signature};
 ///
 /// [`ImportsBuilder`]: struct.ImportsBuilder.html
 pub trait ImportResolver {
+    /// Resolve a function.
+    ///
+    /// Returned function should match given `signature`, i.e. all parameter types and return value should have exact match.
+    /// Otherwise, link-time error will occur.
+    fn resolve_func(
+        &self,
+        _module_name: &str,
+        field_name: &str,
+        _signature: &Signature,
+    ) -> Result<FuncRef, Error>;
 
-	/// Resolve a function.
-	///
-	/// Returned function should match given `signature`, i.e. all parameter types and return value should have exact match.
-	/// Otherwise, link-time error will occur.
-	fn resolve_func(
-		&self,
-		_module_name: &str,
-		field_name: &str,
-		_signature: &Signature,
-	) -> Result<FuncRef, Error>;
+    /// Resolve a global variable.
+    ///
+    /// Returned global should match given `descriptor`, i.e. type and mutability
+    /// should match. Otherwise, link-time error will occur.
+    fn resolve_global(
+        &self,
+        module_name: &str,
+        field_name: &str,
+        descriptor: &GlobalDescriptor,
+    ) -> Result<GlobalRef, Error>;
 
-	/// Resolve a global variable.
-	///
-	/// Returned global should match given `descriptor`, i.e. type and mutability
-	/// should match. Otherwise, link-time error will occur.
-	fn resolve_global(
-		&self,
-		module_name: &str,
-		field_name: &str,
-		descriptor: &GlobalDescriptor,
-	) -> Result<GlobalRef, Error>;
+    /// Resolve a memory.
+    ///
+    /// Returned memory should match requested memory (described by the `descriptor`),
+    /// i.e. initial size of a returned memory should be equal or larger than requested memory.
+    /// Furthermore, if requested memory have maximum size, returned memory either should have
+    /// equal or larger maximum size or have no maximum size at all.
+    /// If returned memory doesn't match the requested then link-time error will occur.
+    fn resolve_memory(
+        &self,
+        module_name: &str,
+        field_name: &str,
+        descriptor: &MemoryDescriptor,
+    ) -> Result<MemoryRef, Error>;
 
-	/// Resolve a memory.
-	///
-	/// Returned memory should match requested memory (described by the `descriptor`),
-	/// i.e. initial size of a returned memory should be equal or larger than requested memory.
-	/// Furthermore, if requested memory have maximum size, returned memory either should have
-	/// equal or larger maximum size or have no maximum size at all.
-	/// If returned memory doesn't match the requested then link-time error will occur.
-	fn resolve_memory(
-		&self,
-		module_name: &str,
-		field_name: &str,
-		descriptor: &MemoryDescriptor,
-	) -> Result<MemoryRef, Error>;
-
-	/// Resolve a table.
-	///
-	/// Returned table should match requested table (described by the `descriptor`),
-	/// i.e. initial size of a returned table should be equal or larger than requested table.
-	/// Furthermore, if requested memory have maximum size, returned memory either should have
-	/// equal or larger maximum size or have no maximum size at all.
-	/// If returned table doesn't match the requested then link-time error will occur.
-	fn resolve_table(
-		&self,
-		module_name: &str,
-		field_name: &str,
-		descriptor: &TableDescriptor,
-	) -> Result<TableRef, Error>;
+    /// Resolve a table.
+    ///
+    /// Returned table should match requested table (described by the `descriptor`),
+    /// i.e. initial size of a returned table should be equal or larger than requested table.
+    /// Furthermore, if requested memory have maximum size, returned memory either should have
+    /// equal or larger maximum size or have no maximum size at all.
+    /// If returned table doesn't match the requested then link-time error will occur.
+    fn resolve_table(
+        &self,
+        module_name: &str,
+        field_name: &str,
+        descriptor: &TableDescriptor,
+    ) -> Result<TableRef, Error>;
 }
 
 /// Convenience builder of [`ImportResolver`].
@@ -101,216 +100,212 @@ pub trait ImportResolver {
 /// [`ImportResolver`]: trait.ImportResolver.html
 /// [`ModuleImportResolver`]: trait.ModuleImportResolver.html
 pub struct ImportsBuilder<'a> {
-	modules: HashMap<String, &'a ModuleImportResolver>,
+    modules: BTreeMap<String, &'a dyn ModuleImportResolver>,
 }
 
 impl<'a> Default for ImportsBuilder<'a> {
-	fn default() -> Self {
-		Self::new()
-	}
+    fn default() -> Self {
+        Self::new()
+    }
 }
 
 impl<'a> ImportsBuilder<'a> {
-	/// Create an empty `ImportsBuilder`.
-	pub fn new() -> ImportsBuilder<'a> {
-		ImportsBuilder { modules: HashMap::new() }
-	}
+    /// Create an empty `ImportsBuilder`.
+    pub fn new() -> ImportsBuilder<'a> {
+        ImportsBuilder {
+            modules: BTreeMap::new(),
+        }
+    }
 
-	/// Register an resolver by a name.
-	pub fn with_resolver<N: Into<String>>(
-		mut self,
-		name: N,
-		resolver: &'a ModuleImportResolver,
-	) -> Self {
-		self.modules.insert(name.into(), resolver);
-		self
-	}
+    /// Register an resolver by a name.
+    pub fn with_resolver<N: Into<String>>(
+        mut self,
+        name: N,
+        resolver: &'a dyn ModuleImportResolver,
+    ) -> Self {
+        self.modules.insert(name.into(), resolver);
+        self
+    }
 
-	/// Register an resolver by a name.
-	///
-	/// Mutable borrowed version.
-	pub fn push_resolver<N: Into<String>>(&mut self, name: N, resolver: &'a ModuleImportResolver) {
-		self.modules.insert(name.into(), resolver);
-	}
+    /// Register an resolver by a name.
+    ///
+    /// Mutable borrowed version.
+    pub fn push_resolver<N: Into<String>>(
+        &mut self,
+        name: N,
+        resolver: &'a dyn ModuleImportResolver,
+    ) {
+        self.modules.insert(name.into(), resolver);
+    }
 
-	fn resolver(&self, name: &str) -> Option<&ModuleImportResolver> {
-		self.modules.get(name).cloned()
-	}
+    fn resolver(&self, name: &str) -> Option<&dyn ModuleImportResolver> {
+        self.modules.get(name).cloned()
+    }
 }
 
 impl<'a> ImportResolver for ImportsBuilder<'a> {
-	fn resolve_func(
-		&self,
-		module_name: &str,
-		field_name: &str,
-		signature: &Signature,
-	) -> Result<FuncRef, Error> {
-		self.resolver(module_name).ok_or_else(||
-			Error::Instantiation(format!("Module {} not found", module_name))
-		)?.resolve_func(field_name, signature)
-	}
+    fn resolve_func(
+        &self,
+        module_name: &str,
+        field_name: &str,
+        signature: &Signature,
+    ) -> Result<FuncRef, Error> {
+        self.resolver(module_name)
+            .ok_or_else(|| Error::Instantiation(format!("Module {} not found", module_name)))?
+            .resolve_func(field_name, signature)
+    }
 
-	fn resolve_global(
-		&self,
-		module_name: &str,
-		field_name: &str,
-		global_type: &GlobalDescriptor,
-	) -> Result<GlobalRef, Error> {
-		self.resolver(module_name).ok_or_else(||
-			Error::Instantiation(format!("Module {} not found", module_name))
-		)?.resolve_global(field_name, global_type)
-	}
+    fn resolve_global(
+        &self,
+        module_name: &str,
+        field_name: &str,
+        global_type: &GlobalDescriptor,
+    ) -> Result<GlobalRef, Error> {
+        self.resolver(module_name)
+            .ok_or_else(|| Error::Instantiation(format!("Module {} not found", module_name)))?
+            .resolve_global(field_name, global_type)
+    }
 
-	fn resolve_memory(
-		&self,
-		module_name: &str,
-		field_name: &str,
-		memory_type: &MemoryDescriptor,
-	) -> Result<MemoryRef, Error> {
-		self.resolver(module_name).ok_or_else(||
-			Error::Instantiation(format!("Module {} not found", module_name))
-		)?.resolve_memory(field_name, memory_type)
-	}
+    fn resolve_memory(
+        &self,
+        module_name: &str,
+        field_name: &str,
+        memory_type: &MemoryDescriptor,
+    ) -> Result<MemoryRef, Error> {
+        self.resolver(module_name)
+            .ok_or_else(|| Error::Instantiation(format!("Module {} not found", module_name)))?
+            .resolve_memory(field_name, memory_type)
+    }
 
-	fn resolve_table(
-		&self,
-		module_name: &str,
-		field_name: &str,
-		table_type: &TableDescriptor,
-	) -> Result<TableRef, Error> {
-		self.resolver(module_name).ok_or_else(||
-			Error::Instantiation(format!("Module {} not found", module_name))
-		)?.resolve_table(field_name, table_type)
-	}
+    fn resolve_table(
+        &self,
+        module_name: &str,
+        field_name: &str,
+        table_type: &TableDescriptor,
+    ) -> Result<TableRef, Error> {
+        self.resolver(module_name)
+            .ok_or_else(|| Error::Instantiation(format!("Module {} not found", module_name)))?
+            .resolve_table(field_name, table_type)
+    }
 }
 
 /// Version of [`ImportResolver`] specialized for a single module.
 ///
 /// [`ImportResolver`]: trait.ImportResolver.html
 pub trait ModuleImportResolver {
-	/// Resolve a function.
-	///
-	/// See [`ImportResolver::resolve_func`] for details.
-	///
-	/// [`ImportResolver::resolve_func`]: trait.ImportResolver.html#tymethod.resolve_func
-	fn resolve_func(
-		&self,
-		field_name: &str,
-		_signature: &Signature,
-	) -> Result<FuncRef, Error> {
-		Err(Error::Instantiation(
-			format!("Export {} not found", field_name),
-		))
-	}
+    /// Resolve a function.
+    ///
+    /// See [`ImportResolver::resolve_func`] for details.
+    ///
+    /// [`ImportResolver::resolve_func`]: trait.ImportResolver.html#tymethod.resolve_func
+    fn resolve_func(&self, field_name: &str, _signature: &Signature) -> Result<FuncRef, Error> {
+        Err(Error::Instantiation(format!(
+            "Export {} not found",
+            field_name
+        )))
+    }
 
-	/// Resolve a global variable.
-	///
-	/// See [`ImportResolver::resolve_global`] for details.
-	///
-	/// [`ImportResolver::resolve_global`]: trait.ImportResolver.html#tymethod.resolve_global
-	fn resolve_global(
-		&self,
-		field_name: &str,
-		_global_type: &GlobalDescriptor,
-	) -> Result<GlobalRef, Error> {
-		Err(Error::Instantiation(
-			format!("Export {} not found", field_name),
-		))
-	}
+    /// Resolve a global variable.
+    ///
+    /// See [`ImportResolver::resolve_global`] for details.
+    ///
+    /// [`ImportResolver::resolve_global`]: trait.ImportResolver.html#tymethod.resolve_global
+    fn resolve_global(
+        &self,
+        field_name: &str,
+        _global_type: &GlobalDescriptor,
+    ) -> Result<GlobalRef, Error> {
+        Err(Error::Instantiation(format!(
+            "Export {} not found",
+            field_name
+        )))
+    }
 
-	/// Resolve a memory.
-	///
-	/// See [`ImportResolver::resolve_memory`] for details.
-	///
-	/// [`ImportResolver::resolve_memory`]: trait.ImportResolver.html#tymethod.resolve_memory
-	fn resolve_memory(
-		&self,
-		field_name: &str,
-		_memory_type: &MemoryDescriptor,
-	) -> Result<MemoryRef, Error> {
-		Err(Error::Instantiation(
-			format!("Export {} not found", field_name),
-		))
-	}
+    /// Resolve a memory.
+    ///
+    /// See [`ImportResolver::resolve_memory`] for details.
+    ///
+    /// [`ImportResolver::resolve_memory`]: trait.ImportResolver.html#tymethod.resolve_memory
+    fn resolve_memory(
+        &self,
+        field_name: &str,
+        _memory_type: &MemoryDescriptor,
+    ) -> Result<MemoryRef, Error> {
+        Err(Error::Instantiation(format!(
+            "Export {} not found",
+            field_name
+        )))
+    }
 
-	/// Resolve a table.
-	///
-	/// See [`ImportResolver::resolve_table`] for details.
-	///
-	/// [`ImportResolver::resolve_table`]: trait.ImportResolver.html#tymethod.resolve_table
-	fn resolve_table(
-		&self,
-		field_name: &str,
-		_table_type: &TableDescriptor,
-	) -> Result<TableRef, Error> {
-		Err(Error::Instantiation(
-			format!("Export {} not found", field_name),
-		))
-	}
+    /// Resolve a table.
+    ///
+    /// See [`ImportResolver::resolve_table`] for details.
+    ///
+    /// [`ImportResolver::resolve_table`]: trait.ImportResolver.html#tymethod.resolve_table
+    fn resolve_table(
+        &self,
+        field_name: &str,
+        _table_type: &TableDescriptor,
+    ) -> Result<TableRef, Error> {
+        Err(Error::Instantiation(format!(
+            "Export {} not found",
+            field_name
+        )))
+    }
 }
 
 impl ModuleImportResolver for ModuleRef {
-	fn resolve_func(
-		&self,
-		field_name: &str,
-		_signature: &Signature,
-	) -> Result<FuncRef, Error> {
-		Ok(self.export_by_name(field_name)
-			.ok_or_else(|| {
-				Error::Instantiation(format!("Export {} not found", field_name))
-			})?
-			.as_func()
-			.cloned()
-			.ok_or_else(|| {
-				Error::Instantiation(format!("Export {} is not a function", field_name))
-			})?)
-	}
+    fn resolve_func(&self, field_name: &str, _signature: &Signature) -> Result<FuncRef, Error> {
+        Ok(self
+            .export_by_name(field_name)
+            .ok_or_else(|| Error::Instantiation(format!("Export {} not found", field_name)))?
+            .as_func()
+            .cloned()
+            .ok_or_else(|| {
+                Error::Instantiation(format!("Export {} is not a function", field_name))
+            })?)
+    }
 
-	fn resolve_global(
-		&self,
-		field_name: &str,
-		_global_type: &GlobalDescriptor,
-	) -> Result<GlobalRef, Error> {
-		Ok(self.export_by_name(field_name)
-			.ok_or_else(|| {
-				Error::Instantiation(format!("Export {} not found", field_name))
-			})?
-			.as_global()
-			.cloned()
-			.ok_or_else(|| {
-				Error::Instantiation(format!("Export {} is not a global", field_name))
-			})?)
-	}
+    fn resolve_global(
+        &self,
+        field_name: &str,
+        _global_type: &GlobalDescriptor,
+    ) -> Result<GlobalRef, Error> {
+        Ok(self
+            .export_by_name(field_name)
+            .ok_or_else(|| Error::Instantiation(format!("Export {} not found", field_name)))?
+            .as_global()
+            .cloned()
+            .ok_or_else(|| {
+                Error::Instantiation(format!("Export {} is not a global", field_name))
+            })?)
+    }
 
-	fn resolve_memory(
-		&self,
-		field_name: &str,
-		_memory_type: &MemoryDescriptor,
-	) -> Result<MemoryRef, Error> {
-		Ok(self.export_by_name(field_name)
-			.ok_or_else(|| {
-				Error::Instantiation(format!("Export {} not found", field_name))
-			})?
-			.as_memory()
-			.cloned()
-			.ok_or_else(|| {
-				Error::Instantiation(format!("Export {} is not a memory", field_name))
-			})?)
-	}
+    fn resolve_memory(
+        &self,
+        field_name: &str,
+        _memory_type: &MemoryDescriptor,
+    ) -> Result<MemoryRef, Error> {
+        Ok(self
+            .export_by_name(field_name)
+            .ok_or_else(|| Error::Instantiation(format!("Export {} not found", field_name)))?
+            .as_memory()
+            .cloned()
+            .ok_or_else(|| {
+                Error::Instantiation(format!("Export {} is not a memory", field_name))
+            })?)
+    }
 
-	fn resolve_table(
-		&self,
-		field_name: &str,
-		_table_type: &TableDescriptor,
-	) -> Result<TableRef, Error> {
-		Ok(self.export_by_name(field_name)
-			.ok_or_else(|| {
-				Error::Instantiation(format!("Export {} not found", field_name))
-			})?
-			.as_table()
-			.cloned()
-			.ok_or_else(|| {
-				Error::Instantiation(format!("Export {} is not a table", field_name))
-			})?)
-	}
+    fn resolve_table(
+        &self,
+        field_name: &str,
+        _table_type: &TableDescriptor,
+    ) -> Result<TableRef, Error> {
+        Ok(self
+            .export_by_name(field_name)
+            .ok_or_else(|| Error::Instantiation(format!("Export {} not found", field_name)))?
+            .as_table()
+            .cloned()
+            .ok_or_else(|| Error::Instantiation(format!("Export {} is not a table", field_name)))?)
+    }
 }

src/isa.rs

@@ -0,0 +1,802 @@
+//! An instruction set used by wasmi.
+//!
+//! The instruction set is mostly derived from Wasm. However,
+//! there is a substantial difference.
+//!
+//! # Structured Stack Machine vs Plain One
+//!
+//! Wasm is a structured stack machine. Wasm encodes control flow in structures
+//! similar to that commonly found in a programming languages
+//! such as if, while. That contrasts to a plain stack machine which
+//!  encodes all control flow with goto-like instructions.
+//!
+//! Structured stack machine code aligns well with goals of Wasm,
+//! namely providing fast validation of Wasm code and compilation to native code.
+//!
+//! Unfortunately, the downside of structured stack machine code is
+//! that it is less convenient to interpret. For example, let's look at
+//! the following example in hypothetical structured stack machine:
+//!
+//! ```plain
+//! loop
+//!   ...
+//!   if_true_jump_to_end
+//!   ...
+//! end
+//! ```
+//!
+//! To execute `if_true_jump_to_end` , the interpreter needs to skip all instructions
+//! until it reaches the *matching* `end`. That's quite inefficient compared
+//! to a plain goto to the specific position.
+//!
+//! Because of this, the translation from the Wasm structured stack machine into a
+//! plain one is taking place.
+//!
+//! # Locals
+//!
+//! In a plain stack machine local variables and arguments live on the stack. Instead of
+//! accessing predefined locals slots in a plain stack machine locals are addressed relative
+//! to the current stack pointer. Because of this instead of taking an index of a local
+//! in {get,set,tee}_local operations, they take a relative depth as immediate. This works
+//! because at each instruction we always know the current stack height.
+//!
+//! Roughly, the stack layout looks like this
+//!
+//! | caller arguments |
+//! |  - arg 1         |
+//! |  - arg 2         |
+//! +------------------+
+//! | callee locals    |
+//! |  - var 1         |
+//! |  - var 2         |
+//! +------------------+
+//! | operands         |
+//! |  - op 1          |
+//! |  - op 2          |
+//! |                  |  <-- current stack pointer
+//! +------------------+
+//!
+//! # Differences from Wasm
+//!
+//! - There is no `nop` instruction.
+//! - All control flow structures are flattened to plain gotos.
+//! - Implicit returns via reaching function scope `End` are replaced with an explicit `return` instruction.
+//! - Locals live on the value stack now.
+//! - Load/store instructions doesn't take `align` parameter.
+//! - *.const store value in straight encoding.
+//! - Reserved immediates are ignored for `call_indirect`, `current_memory`, `grow_memory`.
+//!
+
+use alloc::vec::Vec;
+
+/// Should we keep a value before "discarding" a stack frame?
+///
+/// Note that this is a `enum` since Wasm doesn't support multiple return
+/// values at the moment.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum Keep {
+    None,
+    /// Pop one value from the yet-to-be-discarded stack frame to the
+    /// current stack frame.
+    Single,
+}
+
+impl Keep {
+    /// Reutrns a number of items that should be kept on the stack.
+    pub fn count(&self) -> u32 {
+        match *self {
+            Keep::None => 0,
+            Keep::Single => 1,
+        }
+    }
+}
+
+/// Specifies how many values we should keep and how many we should drop.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub struct DropKeep {
+    pub drop: u32,
+    pub keep: Keep,
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub struct Target {
+    pub dst_pc: u32,
+    pub drop_keep: DropKeep,
+}
+
+/// A relocation entry that specifies.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum Reloc {
+    /// Patch the destination of the branch instruction (br, br_eqz, br_nez)
+    /// at the specified pc.
+    Br { pc: u32 },
+    /// Patch the specified destination index inside of br_table instruction at
+    /// the specified pc.
+    BrTable { pc: u32, idx: usize },
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub struct BrTargets<'a> {
+    stream: &'a [InstructionInternal],
+}
+
+impl<'a> BrTargets<'a> {
+    pub(crate) fn from_internal(targets: &'a [InstructionInternal]) -> Self {
+        BrTargets { stream: targets }
+    }
+
+    #[inline]
+    pub fn get(&self, index: u32) -> Target {
+        match self.stream[index.min(self.stream.len() as u32 - 1) as usize] {
+            InstructionInternal::BrTableTarget(target) => target,
+            _ => panic!("BrTable has incorrect target count"),
+        }
+    }
+}
+
+/// The main interpreted instruction type. This is what is returned by `InstructionIter`, but
+/// it is not what is stored internally. For that, see `InstructionInternal`.
+#[derive(Debug, Clone, PartialEq)]
+pub enum Instruction<'a> {
+    /// Push a local variable or an argument from the specified depth.
+    GetLocal(u32),
+
+    /// Pop a value and put it in at the specified depth.
+    SetLocal(u32),
+
+    /// Copy a value to the specified depth.
+    TeeLocal(u32),
+
+    /// Similar to the Wasm ones, but instead of a label depth
+    /// they specify direct PC.
+    Br(Target),
+    BrIfEqz(Target),
+    BrIfNez(Target),
+
+    /// br_table [t1 t2 t3 .. tn] tdefault
+    ///
+    /// Pops the value from the stack. Then this value is used as an index
+    /// to the branch table.
+    ///
+    /// However, the last target represents the default target. So if the index
+    /// is greater than length of the branch table, then the last index will be used.
+    ///
+    /// Validation ensures that there should be at least one target.
+    BrTable(BrTargets<'a>),
+
+    Unreachable,
+    Return(DropKeep),
+
+    Call(u32),
+    CallIndirect(u32),
+
+    Drop,
+    Select,
+
+    GetGlobal(u32),
+    SetGlobal(u32),
+
+    I32Load(u32),
+    I64Load(u32),
+    F32Load(u32),
+    F64Load(u32),
+    I32Load8S(u32),
+    I32Load8U(u32),
+    I32Load16S(u32),
+    I32Load16U(u32),
+    I64Load8S(u32),
+    I64Load8U(u32),
+    I64Load16S(u32),
+    I64Load16U(u32),
+    I64Load32S(u32),
+    I64Load32U(u32),
+    I32Store(u32),
+    I64Store(u32),
+    F32Store(u32),
+    F64Store(u32),
+    I32Store8(u32),
+    I32Store16(u32),
+    I64Store8(u32),
+    I64Store16(u32),
+    I64Store32(u32),
+
+    CurrentMemory,
+    GrowMemory,
+
+    I32Const(i32),
+    I64Const(i64),
+    F32Const(u32),
+    F64Const(u64),
+
+    I32Eqz,
+    I32Eq,
+    I32Ne,
+    I32LtS,
+    I32LtU,
+    I32GtS,
+    I32GtU,
+    I32LeS,
+    I32LeU,
+    I32GeS,
+    I32GeU,
+
+    I64Eqz,
+    I64Eq,
+    I64Ne,
+    I64LtS,
+    I64LtU,
+    I64GtS,
+    I64GtU,
+    I64LeS,
+    I64LeU,
+    I64GeS,
+    I64GeU,
+
+    F32Eq,
+    F32Ne,
+    F32Lt,
+    F32Gt,
+    F32Le,
+    F32Ge,
+
+    F64Eq,
+    F64Ne,
+    F64Lt,
+    F64Gt,
+    F64Le,
+    F64Ge,
+
+    I32Clz,
+    I32Ctz,
+    I32Popcnt,
+    I32Add,
+    I32Sub,
+    I32Mul,
+    I32DivS,
+    I32DivU,
+    I32RemS,
+    I32RemU,
+    I32And,
+    I32Or,
+    I32Xor,
+    I32Shl,
+    I32ShrS,
+    I32ShrU,
+    I32Rotl,
+    I32Rotr,
+
+    I64Clz,
+    I64Ctz,
+    I64Popcnt,
+    I64Add,
+    I64Sub,
+    I64Mul,
+    I64DivS,
+    I64DivU,
+    I64RemS,
+    I64RemU,
+    I64And,
+    I64Or,
+    I64Xor,
+    I64Shl,
+    I64ShrS,
+    I64ShrU,
+    I64Rotl,
+    I64Rotr,
+    F32Abs,
+    F32Neg,
+    F32Ceil,
+    F32Floor,
+    F32Trunc,
+    F32Nearest,
+    F32Sqrt,
+    F32Add,
+    F32Sub,
+    F32Mul,
+    F32Div,
+    F32Min,
+    F32Max,
+    F32Copysign,
+    F64Abs,
+    F64Neg,
+    F64Ceil,
+    F64Floor,
+    F64Trunc,
+    F64Nearest,
+    F64Sqrt,
+    F64Add,
+    F64Sub,
+    F64Mul,
+    F64Div,
+    F64Min,
+    F64Max,
+    F64Copysign,
+
+    I32WrapI64,
+    I32TruncSF32,
+    I32TruncUF32,
+    I32TruncSF64,
+    I32TruncUF64,
+    I64ExtendSI32,
+    I64ExtendUI32,
+    I64TruncSF32,
+    I64TruncUF32,
+    I64TruncSF64,
+    I64TruncUF64,
+    F32ConvertSI32,
+    F32ConvertUI32,
+    F32ConvertSI64,
+    F32ConvertUI64,
+    F32DemoteF64,
+    F64ConvertSI32,
+    F64ConvertUI32,
+    F64ConvertSI64,
+    F64ConvertUI64,
+    F64PromoteF32,
+
+    I32ReinterpretF32,
+    I64ReinterpretF64,
+    F32ReinterpretI32,
+    F64ReinterpretI64,
+}
+
+/// The internally-stored instruction type. This differs from `Instruction` in that the `BrTable`
+/// target list is "unrolled" into seperate instructions in order to be able to A) improve cache
+/// usage and B) allow this struct to be `Copy` and therefore allow `Instructions::clone` to be
+/// a `memcpy`. It also means that `Instructions::drop` is trivial. The overall speedup on some
+/// benchmarks is as high as 13%.
+///
+/// When returning instructions we convert to `Instruction`, whose `BrTable` variant internally
+/// borrows the list of instructions and returns targets by reading it.
+#[derive(Copy, Debug, Clone, PartialEq, Eq)]
+pub(crate) enum InstructionInternal {
+    GetLocal(u32),
+    SetLocal(u32),
+    TeeLocal(u32),
+    Br(Target),
+    BrIfEqz(Target),
+    BrIfNez(Target),
+    BrTable { count: u32 },
+    BrTableTarget(Target),
+
+    Unreachable,
+    Return(DropKeep),
+
+    Call(u32),
+    CallIndirect(u32),
+
+    Drop,
+    Select,
+
+    GetGlobal(u32),
+    SetGlobal(u32),
+
+    I32Load(u32),
+    I64Load(u32),
+    F32Load(u32),
+    F64Load(u32),
+    I32Load8S(u32),
+    I32Load8U(u32),
+    I32Load16S(u32),
+    I32Load16U(u32),
+    I64Load8S(u32),
+    I64Load8U(u32),
+    I64Load16S(u32),
+    I64Load16U(u32),
+    I64Load32S(u32),
+    I64Load32U(u32),
+    I32Store(u32),
+    I64Store(u32),
+    F32Store(u32),
+    F64Store(u32),
+    I32Store8(u32),
+    I32Store16(u32),
+    I64Store8(u32),
+    I64Store16(u32),
+    I64Store32(u32),
+
+    CurrentMemory,
+    GrowMemory,
+
+    I32Const(i32),
+    I64Const(i64),
+    F32Const(u32),
+    F64Const(u64),
+
+    I32Eqz,
+    I32Eq,
+    I32Ne,
+    I32LtS,
+    I32LtU,
+    I32GtS,
+    I32GtU,
+    I32LeS,
+    I32LeU,
+    I32GeS,
+    I32GeU,
+
+    I64Eqz,
+    I64Eq,
+    I64Ne,
+    I64LtS,
+    I64LtU,
+    I64GtS,
+    I64GtU,
+    I64LeS,
+    I64LeU,
+    I64GeS,
+    I64GeU,
+
+    F32Eq,
+    F32Ne,
+    F32Lt,
+    F32Gt,
+    F32Le,
+    F32Ge,
+
+    F64Eq,
+    F64Ne,
+    F64Lt,
+    F64Gt,
+    F64Le,
+    F64Ge,
+
+    I32Clz,
+    I32Ctz,
+    I32Popcnt,
+    I32Add,
+    I32Sub,
+    I32Mul,
+    I32DivS,
+    I32DivU,
+    I32RemS,
+    I32RemU,
+    I32And,
+    I32Or,
+    I32Xor,
+    I32Shl,
+    I32ShrS,
+    I32ShrU,
+    I32Rotl,
+    I32Rotr,
+
+    I64Clz,
+    I64Ctz,
+    I64Popcnt,
+    I64Add,
+    I64Sub,
+    I64Mul,
+    I64DivS,
+    I64DivU,
+    I64RemS,
+    I64RemU,
+    I64And,
+    I64Or,
+    I64Xor,
+    I64Shl,
+    I64ShrS,
+    I64ShrU,
+    I64Rotl,
+    I64Rotr,
+    F32Abs,
+    F32Neg,
+    F32Ceil,
+    F32Floor,
+    F32Trunc,
+    F32Nearest,
+    F32Sqrt,
+    F32Add,
+    F32Sub,
+    F32Mul,
+    F32Div,
+    F32Min,
+    F32Max,
+    F32Copysign,
+    F64Abs,
+    F64Neg,
+    F64Ceil,
+    F64Floor,
+    F64Trunc,
+    F64Nearest,
+    F64Sqrt,
+    F64Add,
+    F64Sub,
+    F64Mul,
+    F64Div,
+    F64Min,
+    F64Max,
+    F64Copysign,
+
+    I32WrapI64,
+    I32TruncSF32,
+    I32TruncUF32,
+    I32TruncSF64,
+    I32TruncUF64,
+    I64ExtendSI32,
+    I64ExtendUI32,
+    I64TruncSF32,
+    I64TruncUF32,
+    I64TruncSF64,
+    I64TruncUF64,
+    F32ConvertSI32,
+    F32ConvertUI32,
+    F32ConvertSI64,
+    F32ConvertUI64,
+    F32DemoteF64,
+    F64ConvertSI32,
+    F64ConvertUI32,
+    F64ConvertSI64,
+    F64ConvertUI64,
+    F64PromoteF32,
+
+    I32ReinterpretF32,
+    I64ReinterpretF64,
+    F32ReinterpretI32,
+    F64ReinterpretI64,
+}
+
+#[derive(Debug, Clone)]
+pub struct Instructions {
+    vec: Vec<InstructionInternal>,
+}
+
+impl Instructions {
+    pub fn with_capacity(capacity: usize) -> Self {
+        Instructions {
+            vec: Vec::with_capacity(capacity),
+        }
+    }
+
+    pub fn current_pc(&self) -> u32 {
+        self.vec.len() as u32
+    }
+
+    pub(crate) fn push(&mut self, instruction: InstructionInternal) {
+        self.vec.push(instruction);
+    }
+
+    pub fn patch_relocation(&mut self, reloc: Reloc, dst_pc: u32) {
+        match reloc {
+            Reloc::Br { pc } => match self.vec[pc as usize] {
+                InstructionInternal::Br(ref mut target)
+                | InstructionInternal::BrIfEqz(ref mut target)
+                | InstructionInternal::BrIfNez(ref mut target) => target.dst_pc = dst_pc,
+                _ => panic!("branch relocation points to a non-branch instruction"),
+            },
+            Reloc::BrTable { pc, idx } => match &mut self.vec[pc as usize + idx + 1] {
+                InstructionInternal::BrTableTarget(target) => target.dst_pc = dst_pc,
+                _ => panic!("brtable relocation points to not brtable instruction"),
+            },
+        }
+    }
+
+    pub fn iterate_from(&self, position: u32) -> InstructionIter {
+        InstructionIter {
+            instructions: &self.vec,
+            position,
+        }
+    }
+}
+
+pub struct InstructionIter<'a> {
+    instructions: &'a [InstructionInternal],
+    position: u32,
+}
+
+impl<'a> InstructionIter<'a> {
+    #[inline]
+    pub fn position(&self) -> u32 {
+        self.position
+    }
+}
+
+impl<'a> Iterator for InstructionIter<'a> {
+    type Item = Instruction<'a>;
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        let internal = if let Some(i) = self.instructions.get(self.position as usize) {
+            i
+        } else {
+            return None;
+        };
+
+        let out = match *internal {
+            InstructionInternal::GetLocal(x) => Instruction::GetLocal(x),
+            InstructionInternal::SetLocal(x) => Instruction::SetLocal(x),
+            InstructionInternal::TeeLocal(x) => Instruction::TeeLocal(x),
+            InstructionInternal::Br(x) => Instruction::Br(x),
+            InstructionInternal::BrIfEqz(x) => Instruction::BrIfEqz(x),
+            InstructionInternal::BrIfNez(x) => Instruction::BrIfNez(x),
+            InstructionInternal::BrTable { count } => {
+                let start = self.position as usize + 1;
+
+                self.position += count;
+
+                Instruction::BrTable(BrTargets::from_internal(
+                    &self.instructions[start..start + count as usize],
+                ))
+            }
+            InstructionInternal::BrTableTarget(_) => panic!("Executed BrTableTarget"),
+
+            InstructionInternal::Unreachable => Instruction::Unreachable,
+            InstructionInternal::Return(x) => Instruction::Return(x),
+
+            InstructionInternal::Call(x) => Instruction::Call(x),
+            InstructionInternal::CallIndirect(x) => Instruction::CallIndirect(x),
+
+            InstructionInternal::Drop => Instruction::Drop,
+            InstructionInternal::Select => Instruction::Select,
+
+            InstructionInternal::GetGlobal(x) => Instruction::GetGlobal(x),
+            InstructionInternal::SetGlobal(x) => Instruction::SetGlobal(x),
+
+            InstructionInternal::I32Load(x) => Instruction::I32Load(x),
+            InstructionInternal::I64Load(x) => Instruction::I64Load(x),
+            InstructionInternal::F32Load(x) => Instruction::F32Load(x),
+            InstructionInternal::F64Load(x) => Instruction::F64Load(x),
+            InstructionInternal::I32Load8S(x) => Instruction::I32Load8S(x),
+            InstructionInternal::I32Load8U(x) => Instruction::I32Load8U(x),
+            InstructionInternal::I32Load16S(x) => Instruction::I32Load16S(x),
+            InstructionInternal::I32Load16U(x) => Instruction::I32Load16U(x),
+            InstructionInternal::I64Load8S(x) => Instruction::I64Load8S(x),
+            InstructionInternal::I64Load8U(x) => Instruction::I64Load8U(x),
+            InstructionInternal::I64Load16S(x) => Instruction::I64Load16S(x),
+            InstructionInternal::I64Load16U(x) => Instruction::I64Load16U(x),
+            InstructionInternal::I64Load32S(x) => Instruction::I64Load32S(x),
+            InstructionInternal::I64Load32U(x) => Instruction::I64Load32U(x),
+            InstructionInternal::I32Store(x) => Instruction::I32Store(x),
+            InstructionInternal::I64Store(x) => Instruction::I64Store(x),
+            InstructionInternal::F32Store(x) => Instruction::F32Store(x),
+            InstructionInternal::F64Store(x) => Instruction::F64Store(x),
+            InstructionInternal::I32Store8(x) => Instruction::I32Store8(x),
+            InstructionInternal::I32Store16(x) => Instruction::I32Store16(x),
+            InstructionInternal::I64Store8(x) => Instruction::I64Store8(x),
+            InstructionInternal::I64Store16(x) => Instruction::I64Store16(x),
+            InstructionInternal::I64Store32(x) => Instruction::I64Store32(x),
+
+            InstructionInternal::CurrentMemory => Instruction::CurrentMemory,
+            InstructionInternal::GrowMemory => Instruction::GrowMemory,
+
+            InstructionInternal::I32Const(x) => Instruction::I32Const(x),
+            InstructionInternal::I64Const(x) => Instruction::I64Const(x),
+            InstructionInternal::F32Const(x) => Instruction::F32Const(x),
+            InstructionInternal::F64Const(x) => Instruction::F64Const(x),
+
+            InstructionInternal::I32Eqz => Instruction::I32Eqz,
+            InstructionInternal::I32Eq => Instruction::I32Eq,
+            InstructionInternal::I32Ne => Instruction::I32Ne,
+            InstructionInternal::I32LtS => Instruction::I32LtS,
+            InstructionInternal::I32LtU => Instruction::I32LtU,
+            InstructionInternal::I32GtS => Instruction::I32GtS,
+            InstructionInternal::I32GtU => Instruction::I32GtU,
+            InstructionInternal::I32LeS => Instruction::I32LeS,
+            InstructionInternal::I32LeU => Instruction::I32LeU,
+            InstructionInternal::I32GeS => Instruction::I32GeS,
+            InstructionInternal::I32GeU => Instruction::I32GeU,
+
+            InstructionInternal::I64Eqz => Instruction::I64Eqz,
+            InstructionInternal::I64Eq => Instruction::I64Eq,
+            InstructionInternal::I64Ne => Instruction::I64Ne,
+            InstructionInternal::I64LtS => Instruction::I64LtS,
+            InstructionInternal::I64LtU => Instruction::I64LtU,
+            InstructionInternal::I64GtS => Instruction::I64GtS,
+            InstructionInternal::I64GtU => Instruction::I64GtU,
+            InstructionInternal::I64LeS => Instruction::I64LeS,
+            InstructionInternal::I64LeU => Instruction::I64LeU,
+            InstructionInternal::I64GeS => Instruction::I64GeS,
+            InstructionInternal::I64GeU => Instruction::I64GeU,
+
+            InstructionInternal::F32Eq => Instruction::F32Eq,
+            InstructionInternal::F32Ne => Instruction::F32Ne,
+            InstructionInternal::F32Lt => Instruction::F32Lt,
+            InstructionInternal::F32Gt => Instruction::F32Gt,
+            InstructionInternal::F32Le => Instruction::F32Le,
+            InstructionInternal::F32Ge => Instruction::F32Ge,
+
+            InstructionInternal::F64Eq => Instruction::F64Eq,
+            InstructionInternal::F64Ne => Instruction::F64Ne,
+            InstructionInternal::F64Lt => Instruction::F64Lt,
+            InstructionInternal::F64Gt => Instruction::F64Gt,
+            InstructionInternal::F64Le => Instruction::F64Le,
+            InstructionInternal::F64Ge => Instruction::F64Ge,
+
+            InstructionInternal::I32Clz => Instruction::I32Clz,
+            InstructionInternal::I32Ctz => Instruction::I32Ctz,
+            InstructionInternal::I32Popcnt => Instruction::I32Popcnt,
+            InstructionInternal::I32Add => Instruction::I32Add,
+            InstructionInternal::I32Sub => Instruction::I32Sub,
+            InstructionInternal::I32Mul => Instruction::I32Mul,
+            InstructionInternal::I32DivS => Instruction::I32DivS,
+            InstructionInternal::I32DivU => Instruction::I32DivU,
+            InstructionInternal::I32RemS => Instruction::I32RemS,
+            InstructionInternal::I32RemU => Instruction::I32RemU,
+            InstructionInternal::I32And => Instruction::I32And,
+            InstructionInternal::I32Or => Instruction::I32Or,
+            InstructionInternal::I32Xor => Instruction::I32Xor,
+            InstructionInternal::I32Shl => Instruction::I32Shl,
+            InstructionInternal::I32ShrS => Instruction::I32ShrS,
+            InstructionInternal::I32ShrU => Instruction::I32ShrU,
+            InstructionInternal::I32Rotl => Instruction::I32Rotl,
+            InstructionInternal::I32Rotr => Instruction::I32Rotr,
+
+            InstructionInternal::I64Clz => Instruction::I64Clz,
+            InstructionInternal::I64Ctz => Instruction::I64Ctz,
+            InstructionInternal::I64Popcnt => Instruction::I64Popcnt,
+            InstructionInternal::I64Add => Instruction::I64Add,
+            InstructionInternal::I64Sub => Instruction::I64Sub,
+            InstructionInternal::I64Mul => Instruction::I64Mul,
+            InstructionInternal::I64DivS => Instruction::I64DivS,
+            InstructionInternal::I64DivU => Instruction::I64DivU,
+            InstructionInternal::I64RemS => Instruction::I64RemS,
+            InstructionInternal::I64RemU => Instruction::I64RemU,
+            InstructionInternal::I64And => Instruction::I64And,
+            InstructionInternal::I64Or => Instruction::I64Or,
+            InstructionInternal::I64Xor => Instruction::I64Xor,
+            InstructionInternal::I64Shl => Instruction::I64Shl,
+            InstructionInternal::I64ShrS => Instruction::I64ShrS,
+            InstructionInternal::I64ShrU => Instruction::I64ShrU,
+            InstructionInternal::I64Rotl => Instruction::I64Rotl,
+            InstructionInternal::I64Rotr => Instruction::I64Rotr,
+            InstructionInternal::F32Abs => Instruction::F32Abs,
+            InstructionInternal::F32Neg => Instruction::F32Neg,
+            InstructionInternal::F32Ceil => Instruction::F32Ceil,
+            InstructionInternal::F32Floor => Instruction::F32Floor,
+            InstructionInternal::F32Trunc => Instruction::F32Trunc,
+            InstructionInternal::F32Nearest => Instruction::F32Nearest,
+            InstructionInternal::F32Sqrt => Instruction::F32Sqrt,
+            InstructionInternal::F32Add => Instruction::F32Add,
+            InstructionInternal::F32Sub => Instruction::F32Sub,
+            InstructionInternal::F32Mul => Instruction::F32Mul,
+            InstructionInternal::F32Div => Instruction::F32Div,
+            InstructionInternal::F32Min => Instruction::F32Min,
+            InstructionInternal::F32Max => Instruction::F32Max,
+            InstructionInternal::F32Copysign => Instruction::F32Copysign,
+            InstructionInternal::F64Abs => Instruction::F64Abs,
+            InstructionInternal::F64Neg => Instruction::F64Neg,
+            InstructionInternal::F64Ceil => Instruction::F64Ceil,
+            InstructionInternal::F64Floor => Instruction::F64Floor,
+            InstructionInternal::F64Trunc => Instruction::F64Trunc,
+            InstructionInternal::F64Nearest => Instruction::F64Nearest,
+            InstructionInternal::F64Sqrt => Instruction::F64Sqrt,
+            InstructionInternal::F64Add => Instruction::F64Add,
+            InstructionInternal::F64Sub => Instruction::F64Sub,
+            InstructionInternal::F64Mul => Instruction::F64Mul,
+            InstructionInternal::F64Div => Instruction::F64Div,
+            InstructionInternal::F64Min => Instruction::F64Min,
+            InstructionInternal::F64Max => Instruction::F64Max,
+            InstructionInternal::F64Copysign => Instruction::F64Copysign,
+
+            InstructionInternal::I32WrapI64 => Instruction::I32WrapI64,
+            InstructionInternal::I32TruncSF32 => Instruction::I32TruncSF32,
+            InstructionInternal::I32TruncUF32 => Instruction::I32TruncUF32,
+            InstructionInternal::I32TruncSF64 => Instruction::I32TruncSF64,
+            InstructionInternal::I32TruncUF64 => Instruction::I32TruncUF64,
+            InstructionInternal::I64ExtendSI32 => Instruction::I64ExtendSI32,
+            InstructionInternal::I64ExtendUI32 => Instruction::I64ExtendUI32,
+            InstructionInternal::I64TruncSF32 => Instruction::I64TruncSF32,
+            InstructionInternal::I64TruncUF32 => Instruction::I64TruncUF32,
+            InstructionInternal::I64TruncSF64 => Instruction::I64TruncSF64,
+            InstructionInternal::I64TruncUF64 => Instruction::I64TruncUF64,
+            InstructionInternal::F32ConvertSI32 => Instruction::F32ConvertSI32,
+            InstructionInternal::F32ConvertUI32 => Instruction::F32ConvertUI32,
+            InstructionInternal::F32ConvertSI64 => Instruction::F32ConvertSI64,
+            InstructionInternal::F32ConvertUI64 => Instruction::F32ConvertUI64,
+            InstructionInternal::F32DemoteF64 => Instruction::F32DemoteF64,
+            InstructionInternal::F64ConvertSI32 => Instruction::F64ConvertSI32,
+            InstructionInternal::F64ConvertUI32 => Instruction::F64ConvertUI32,
+            InstructionInternal::F64ConvertSI64 => Instruction::F64ConvertSI64,
+            InstructionInternal::F64ConvertUI64 => Instruction::F64ConvertUI64,
+            InstructionInternal::F64PromoteF32 => Instruction::F64PromoteF32,
+
+            InstructionInternal::I32ReinterpretF32 => Instruction::I32ReinterpretF32,
+            InstructionInternal::I64ReinterpretF64 => Instruction::I64ReinterpretF64,
+            InstructionInternal::F32ReinterpretI32 => Instruction::F32ReinterpretI32,
+            InstructionInternal::F64ReinterpretI64 => Instruction::F64ReinterpretI64,
+        };
+
+        self.position += 1;
+
+        Some(out)
+    }
+}

src/lib.rs

@@ -1,48 +1,48 @@
 //! # wasmi
 //!
-//! This library allows to load WebAssembly modules in binary format and invoke functions on them.
+//! This library allows WebAssembly modules to be loaded in binary format and their functions invoked.
 //!
 //! # Introduction
 //!
-//! WebAssembly (wasm) is a safe, portable, compact format that designed for efficient execution.
+//! WebAssembly (wasm) is a safe, portable and compact format that is designed for efficient execution.
 //!
-//! Wasm code is distributed in a form of modules, that contains definitions of:
+//! Wasm code is distributed in the form of modules that contains definitions of:
 //!
 //! - functions,
 //! - global variables,
-//! - linear memories,
+//! - linear memory instances and
 //! - tables.
 //!
-//! and this definitions can be imported. Also, each definition can be exported.
+//! Each of these definitions can be imported and exported.
 //!
-//! In addition to definitions, modules can define initialization data for their memories or tables that takes the
-//! form of segments copied to given offsets. They can also define a `start` function that is automatically executed.
+//! In addition to these definitions, modules can define initialization data for their memory or tables. This initialization data can take the
+//! form of segments, copied to given offsets. They can also define a `start` function that is automatically executed when the module is loaded.
 //!
 //! ## Loading and Validation
 //!
-//! Before execution a module should be validated. This process checks that module is well-formed
+//! Before execution, a module must be validated. This process checks that the module is well-formed
 //! and makes only allowed operations.
 //!
-//! Valid modules can't access memory out of it's sandbox, can't cause stack underflow
-//! and can call functions only with correct signatures.
+//! A valid module can't access memory outside its sandbox, can't cause stack underflows
+//! and can only call functions with correct signatures.
 //!
-//! ## Instantiatiation
+//! ## Instantiation
 //!
-//! In order to execute code in wasm module it should be instatiated.
+//! In order to execute code from a wasm module, it must be instantiated.
 //! Instantiation includes the following steps:
 //!
-//! 1. Create an empty module instance,
-//! 2. Resolve definition instances for each declared import in the module,
-//! 3. Instantiate definitions declared in the module (e.g. allocate global variables, allocate linear memory, etc),
-//! 4. Initialize memory and table contents by copiying segments into them,
-//! 5. Execute `start` function, if any.
+//! 1. Creating an empty module instance.
+//! 2. Resolving the definition instances for each declared import in the module.
+//! 3. Instantiating definitions declared in the module (e.g. allocate global variables, allocate linear memory, etc.).
+//! 4. Initializing memory and table contents by copying segments into them.
+//! 5. Executing the `start` function, if any.
 //!
-//! After these steps, module instance are ready to execute functions.
+//! After these steps, the module instance is ready to execute functions.
 //!
 //! ## Execution
 //!
-//! It is allowed to only execute functions which are exported by a module.
-//! Functions can either return a result or trap (e.g. there can't be linking-error at the middle of execution).
+//! It only is allowed to call functions which are exported by the module.
+//! Functions can either return a result or trap (e.g. there can't be linking error in the middle of the function execution).
 //! This property is ensured by the validation process.
 //!
 //! # Examples
@@ -72,7 +72,7 @@
 //!         .expect("failed to load wasm");
 //!
 //!     // Instantiate a module with empty imports and
-//!     // asserting that there is no `start` function.
+//!     // assert that there is no `start` function.
 //!     let instance =
 //!         ModuleInstance::new(
 //!             &module,
@@ -81,7 +81,7 @@
 //!         .expect("failed to instantiate wasm module")
 //!         .assert_no_start();
 //!
-//!     // Finally, invoke exported function "test" with no parameters
+//!     // Finally, invoke the exported function "test" with no parameters
 //!     // and empty external function executor.
 //!     assert_eq!(
 //!         instance.invoke_export(
@@ -95,436 +95,470 @@
 //! ```
 
 #![warn(missing_docs)]
+#![cfg_attr(not(feature = "std"), no_std)]
 
+#[cfg(not(feature = "std"))]
+#[macro_use]
+extern crate alloc;
+#[cfg(feature = "std")]
+extern crate std as alloc;
+
+#[cfg(feature = "std")]
+#[macro_use]
+extern crate core;
+
+#[cfg(test)]
+extern crate assert_matches;
 #[cfg(test)]
 extern crate wabt;
-#[cfg(test)]
-#[macro_use]
-extern crate assert_matches;
 
-extern crate parity_wasm;
-extern crate byteorder;
 extern crate memory_units as memory_units_crate;
-extern crate nan_preserving_float;
+extern crate parity_wasm;
 
-use std::fmt;
+extern crate wasmi_validation as validation;
+
+use alloc::{
+    boxed::Box,
+    string::{String, ToString},
+    vec::Vec,
+};
+use core::fmt;
+#[cfg(feature = "std")]
 use std::error;
-use std::collections::HashMap;
 
-/// Error type which can thrown by wasm code or by host environment.
+#[cfg(not(feature = "std"))]
+extern crate libm;
+
+extern crate num_rational;
+extern crate num_traits;
+
+/// Error type which can be thrown by wasm code or by host environment.
 ///
 /// Under some conditions, wasm execution may produce a `Trap`, which immediately aborts execution.
 /// Traps can't be handled by WebAssembly code, but are reported to the embedder.
 #[derive(Debug)]
 pub struct Trap {
-	kind: TrapKind,
+    kind: TrapKind,
 }
 
 impl Trap {
-	/// Create new trap.
-	pub fn new(kind: TrapKind) -> Trap {
-		Trap { kind }
-	}
+    /// Create new trap.
+    pub fn new(kind: TrapKind) -> Trap {
+        Trap { kind }
+    }
 
-	/// Returns kind of this trap.
-	pub fn kind(&self) -> &TrapKind {
-		&self.kind
-	}
+    /// Returns kind of this trap.
+    pub fn kind(&self) -> &TrapKind {
+        &self.kind
+    }
 }
 
 impl fmt::Display for Trap {
-	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-		write!(f, "Trap: {:?}", self.kind)
-	}
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "Trap: {:?}", self.kind)
+    }
 }
 
+#[cfg(feature = "std")]
 impl error::Error for Trap {
-	fn description(&self) -> &str {
-		"runtime trap"
-	}
+    fn description(&self) -> &str {
+        "runtime trap"
+    }
 }
 
-/// Error type which can thrown by wasm code or by host environment.
+/// Error type which can be thrown by wasm code or by host environment.
 ///
 /// See [`Trap`] for details.
 ///
 /// [`Trap`]: struct.Trap.html
 #[derive(Debug)]
 pub enum TrapKind {
-	/// Wasm code executed `unreachable` opcode.
-	///
-	/// `unreachable` is a special opcode which always traps upon execution.
-	/// This opcode have a similar purpose as `ud2` in x86.
-	Unreachable,
+    /// Wasm code executed `unreachable` opcode.
+    ///
+    /// `unreachable` is a special opcode which always traps upon execution.
+    /// This opcode have a similar purpose as `ud2` in x86.
+    Unreachable,
 
-	/// Attempt to load or store at the address which
-	/// lies outside of bounds of the memory.
-	///
-	/// Since addresses are interpreted as unsigned integers, out of bounds access
-	/// can't happen with negative addresses (i.e. they will always wrap).
-	MemoryAccessOutOfBounds,
+    /// Attempt to load or store at the address which
+    /// lies outside of bounds of the memory.
+    ///
+    /// Since addresses are interpreted as unsigned integers, out of bounds access
+    /// can't happen with negative addresses (i.e. they will always wrap).
+    MemoryAccessOutOfBounds,
 
-	/// Attempt to access table element at index which
-	/// lies outside of bounds.
-	///
-	/// This typically can happen when `call_indirect` is executed
-	/// with index that lies out of bounds.
-	///
-	/// Since indexes are interpreted as unsinged integers, out of bounds access
-	/// can't happen with negative indexes (i.e. they will always wrap).
-	TableAccessOutOfBounds,
+    /// Attempt to access table element at index which
+    /// lies outside of bounds.
+    ///
+    /// This typically can happen when `call_indirect` is executed
+    /// with index that lies out of bounds.
+    ///
+    /// Since indexes are interpreted as unsinged integers, out of bounds access
+    /// can't happen with negative indexes (i.e. they will always wrap).
+    TableAccessOutOfBounds,
 
-	/// Attempt to access table element which is uninitialized (i.e. `None`).
-	///
-	/// This typically can happen when `call_indirect` is executed.
-	ElemUninitialized,
+    /// Attempt to access table element which is uninitialized (i.e. `None`).
+    ///
+    /// This typically can happen when `call_indirect` is executed.
+    ElemUninitialized,
 
-	/// Attempt to divide by zero.
-	///
-	/// This trap typically can happen if `div` or `rem` is executed with
-	/// zero as divider.
-	DivisionByZero,
+    /// Attempt to divide by zero.
+    ///
+    /// This trap typically can happen if `div` or `rem` is executed with
+    /// zero as divider.
+    DivisionByZero,
 
-	/// Attempt to make a conversion to an int failed.
-	///
-	/// This can happen when:
-	///
-	/// - trying to do signed division (or get the remainder) -2<sup>N-1</sup> over -1. This is
-	///   because the result +2<sup>N-1</sup> isn't representable as a N-bit signed integer.
-	/// - trying to truncate NaNs, infinity, or value for which the result is out of range into an integer.
-	InvalidConversionToInt,
+    /// Attempt to make a conversion to an int failed.
+    ///
+    /// This can happen when:
+    ///
+    /// - trying to do signed division (or get the remainder) -2<sup>N-1</sup> over -1. This is
+    ///   because the result +2<sup>N-1</sup> isn't representable as a N-bit signed integer.
+    /// - trying to truncate NaNs, infinity, or value for which the result is out of range into an integer.
+    InvalidConversionToInt,
 
-	/// Stack overflow.
-	///
-	/// This is likely caused by some infinite or very deep recursion.
-	/// Extensive inlining might also be the cause of stack overflow.
-	StackOverflow,
+    /// Stack overflow.
+    ///
+    /// This is likely caused by some infinite or very deep recursion.
+    /// Extensive inlining might also be the cause of stack overflow.
+    StackOverflow,
 
-	/// Attempt to invoke a function with mismatching signature.
-	///
-	/// This can happen if [`FuncInstance`] was invoked
-	/// with mismatching [signature][`Signature`].
-	///
-	/// This can always happen with indirect calls. `call_indirect` instruction always
-	/// specifies the expected signature of function. If `call_indirect` is executed
-	/// with index that points on function with signature different that is
-	/// expected by this `call_indirect`, this trap is raised.
-	///
-	/// [`Signature`]: struct.Signature.html
-	UnexpectedSignature,
+    /// Attempt to invoke a function with mismatching signature.
+    ///
+    /// This can happen if [`FuncInstance`] was invoked
+    /// with mismatching [signature][`Signature`].
+    ///
+    /// This can always happen with indirect calls. `call_indirect` instruction always
+    /// specifies the expected signature of function. If `call_indirect` is executed
+    /// with index that points on function with signature different that is
+    /// expected by this `call_indirect`, this trap is raised.
+    ///
+    /// [`Signature`]: struct.Signature.html
+    UnexpectedSignature,
 
-	/// Error specified by the host.
-	///
-	/// Typically returned from an implementation of [`Externals`].
-	///
-	/// [`Externals`]: trait.Externals.html
-	Host(Box<host::HostError>),
+    /// Error specified by the host.
+    ///
+    /// Typically returned from an implementation of [`Externals`].
+    ///
+    /// [`Externals`]: trait.Externals.html
+    Host(Box<dyn host::HostError>),
+}
+
+impl TrapKind {
+    /// Whether this trap is specified by the host.
+    pub fn is_host(&self) -> bool {
+        match self {
+            &TrapKind::Host(_) => true,
+            _ => false,
+        }
+    }
 }
 
 /// Internal interpreter error.
 #[derive(Debug)]
 pub enum Error {
-	/// Module validation error. Might occur only at load time.
-	Validation(String),
-	/// Error while instantiating a module. Might occur when provided
-	/// with incorrect exports (i.e. linkage failure).
-	Instantiation(String),
-	/// Function-level error.
-	Function(String),
-	/// Table-level error.
-	Table(String),
-	/// Memory-level error.
-	Memory(String),
-	/// Global-level error.
-	Global(String),
-	/// Value-level error.
-	Value(String),
-	/// Trap.
-	Trap(Trap),
-	/// Custom embedder error.
-	Host(Box<host::HostError>),
+    /// Module validation error. Might occur only at load time.
+    Validation(String),
+    /// Error while instantiating a module. Might occur when provided
+    /// with incorrect exports (i.e. linkage failure).
+    Instantiation(String),
+    /// Function-level error.
+    Function(String),
+    /// Table-level error.
+    Table(String),
+    /// Memory-level error.
+    Memory(String),
+    /// Global-level error.
+    Global(String),
+    /// Value-level error.
+    Value(String),
+    /// Trap.
+    Trap(Trap),
+    /// Custom embedder error.
+    Host(Box<dyn host::HostError>),
 }
 
 impl Error {
-	/// Returns [`HostError`] if this `Error` represents some host error.
-	///
-	/// I.e. if this error have variant [`Host`] or [`Trap`][`Trap`] with [host][`TrapKind::Host`] error.
-	///
-	/// [`HostError`]: trait.HostError.html
-	/// [`Host`]: enum.Error.html#variant.Host
-	/// [`Trap`]: enum.Error.html#variant.Trap
-	/// [`TrapKind::Host`]: enum.TrapKind.html#variant.Host
-	pub fn as_host_error(&self) -> Option<&host::HostError> {
-		match *self {
-			Error::Host(ref host_err) => Some(&**host_err),
-			Error::Trap(ref trap) => match *trap.kind() {
-				TrapKind::Host(ref host_err) => Some(&**host_err),
-				_ => None,
-			}
-			_ => None,
-		}
-	}
+    /// Returns [`HostError`] if this `Error` represents some host error.
+    ///
+    /// I.e. if this error have variant [`Host`] or [`Trap`][`Trap`] with [host][`TrapKind::Host`] error.
+    ///
+    /// [`HostError`]: trait.HostError.html
+    /// [`Host`]: enum.Error.html#variant.Host
+    /// [`Trap`]: enum.Error.html#variant.Trap
+    /// [`TrapKind::Host`]: enum.TrapKind.html#variant.Host
+    pub fn as_host_error(&self) -> Option<&dyn host::HostError> {
+        match *self {
+            Error::Host(ref host_err) => Some(&**host_err),
+            Error::Trap(ref trap) => match *trap.kind() {
+                TrapKind::Host(ref host_err) => Some(&**host_err),
+                _ => None,
+            },
+            _ => None,
+        }
+    }
 }
 
 impl Into<String> for Error {
-	fn into(self) -> String {
-		match self {
-			Error::Validation(s) => s,
-			Error::Instantiation(s) => s,
-			Error::Function(s) => s,
-			Error::Table(s) => s,
-			Error::Memory(s) => s,
-			Error::Global(s) => s,
-			Error::Value(s) => s,
-			Error::Trap(s) => format!("trap: {:?}", s),
-			Error::Host(e) => format!("user: {}", e),
-		}
-	}
+    fn into(self) -> String {
+        match self {
+            Error::Validation(s) => s,
+            Error::Instantiation(s) => s,
+            Error::Function(s) => s,
+            Error::Table(s) => s,
+            Error::Memory(s) => s,
+            Error::Global(s) => s,
+            Error::Value(s) => s,
+            Error::Trap(s) => format!("trap: {:?}", s),
+            Error::Host(e) => format!("user: {}", e),
+        }
+    }
 }
 
 impl fmt::Display for Error {
-	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-		match *self {
-			Error::Validation(ref s) => write!(f, "Validation: {}", s),
-			Error::Instantiation(ref s) => write!(f, "Instantiation: {}", s),
-			Error::Function(ref s) => write!(f, "Function: {}", s),
-			Error::Table(ref s) => write!(f, "Table: {}", s),
-			Error::Memory(ref s) => write!(f, "Memory: {}", s),
-			Error::Global(ref s) => write!(f, "Global: {}", s),
-			Error::Value(ref s) => write!(f, "Value: {}", s),
-			Error::Trap(ref s) => write!(f, "Trap: {:?}", s),
-			Error::Host(ref e) => write!(f, "User: {}", e),
-		}
-	}
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            Error::Validation(ref s) => write!(f, "Validation: {}", s),
+            Error::Instantiation(ref s) => write!(f, "Instantiation: {}", s),
+            Error::Function(ref s) => write!(f, "Function: {}", s),
+            Error::Table(ref s) => write!(f, "Table: {}", s),
+            Error::Memory(ref s) => write!(f, "Memory: {}", s),
+            Error::Global(ref s) => write!(f, "Global: {}", s),
+            Error::Value(ref s) => write!(f, "Value: {}", s),
+            Error::Trap(ref s) => write!(f, "Trap: {:?}", s),
+            Error::Host(ref e) => write!(f, "User: {}", e),
+        }
+    }
 }
 
+#[cfg(feature = "std")]
 impl error::Error for Error {
-	fn description(&self) -> &str {
-		match *self {
-			Error::Validation(ref s) => s,
-			Error::Instantiation(ref s) => s,
-			Error::Function(ref s) => s,
-			Error::Table(ref s) => s,
-			Error::Memory(ref s) => s,
-			Error::Global(ref s) => s,
-			Error::Value(ref s) => s,
-			Error::Trap(_) => "Trap",
-			Error::Host(_) => "Host error",
-		}
-	}
+    fn description(&self) -> &str {
+        match *self {
+            Error::Validation(ref s) => s,
+            Error::Instantiation(ref s) => s,
+            Error::Function(ref s) => s,
+            Error::Table(ref s) => s,
+            Error::Memory(ref s) => s,
+            Error::Global(ref s) => s,
+            Error::Value(ref s) => s,
+            Error::Trap(_) => "Trap",
+            Error::Host(_) => "Host error",
+        }
+    }
 }
 
-impl<U> From<U> for Error where U: host::HostError + Sized {
-	fn from(e: U) -> Self {
-		Error::Host(Box::new(e))
-	}
+impl<U> From<U> for Error
+where
+    U: host::HostError + Sized,
+{
+    fn from(e: U) -> Self {
+        Error::Host(Box::new(e))
+    }
 }
 
-impl<U> From<U> for Trap where U: host::HostError + Sized {
-	fn from(e: U) -> Self {
-		Trap::new(TrapKind::Host(Box::new(e)))
-	}
+impl<U> From<U> for Trap
+where
+    U: host::HostError + Sized,
+{
+    fn from(e: U) -> Self {
+        Trap::new(TrapKind::Host(Box::new(e)))
+    }
 }
 
 impl From<Trap> for Error {
-	fn from(e: Trap) -> Error {
-		Error::Trap(e)
-	}
+    fn from(e: Trap) -> Error {
+        Error::Trap(e)
+    }
 }
 
 impl From<TrapKind> for Trap {
-	fn from(e: TrapKind) -> Trap {
-		Trap::new(e)
-	}
+    fn from(e: TrapKind) -> Trap {
+        Trap::new(e)
+    }
 }
 
 impl From<validation::Error> for Error {
-	fn from(e: validation::Error) -> Error {
-		Error::Validation(e.to_string())
-	}
+    fn from(e: validation::Error) -> Error {
+        Error::Validation(e.to_string())
+    }
 }
 
-mod validation;
-mod common;
-mod memory;
-mod module;
-mod runner;
-mod table;
-mod value;
+mod func;
+mod global;
 mod host;
 mod imports;
-mod global;
-mod func;
+mod isa;
+mod memory;
+mod module;
+pub mod nan_preserving_float;
+mod prepare;
+mod runner;
+mod table;
 mod types;
+mod value;
 
 #[cfg(test)]
 mod tests;
 
-pub use self::memory::{MemoryInstance, MemoryRef, LINEAR_MEMORY_PAGE_SIZE};
-pub use self::table::{TableInstance, TableRef};
-pub use self::value::{RuntimeValue, FromRuntimeValue};
-pub use self::host::{Externals, NopExternals, HostError, RuntimeArgs};
-pub use self::imports::{ModuleImportResolver, ImportResolver, ImportsBuilder};
-pub use self::module::{ModuleInstance, ModuleRef, ExternVal, NotStartedModuleRef};
+pub use self::func::{FuncInstance, FuncInvocation, FuncRef, ResumableError};
 pub use self::global::{GlobalInstance, GlobalRef};
-pub use self::func::{FuncInstance, FuncRef};
-pub use self::types::{Signature, ValueType, GlobalDescriptor, TableDescriptor, MemoryDescriptor};
+pub use self::host::{Externals, HostError, NopExternals, RuntimeArgs};
+pub use self::imports::{ImportResolver, ImportsBuilder, ModuleImportResolver};
+pub use self::memory::{MemoryInstance, MemoryRef, LINEAR_MEMORY_PAGE_SIZE};
+pub use self::module::{ExternVal, ModuleInstance, ModuleRef, NotStartedModuleRef};
+pub use self::runner::{StackRecycler, DEFAULT_CALL_STACK_LIMIT, DEFAULT_VALUE_STACK_LIMIT};
+pub use self::table::{TableInstance, TableRef};
+pub use self::types::{GlobalDescriptor, MemoryDescriptor, Signature, TableDescriptor, ValueType};
+pub use self::value::{Error as ValueError, FromRuntimeValue, LittleEndianConvert, RuntimeValue};
 
 /// WebAssembly-specific sizes and units.
 pub mod memory_units {
-	pub use memory_units_crate::wasm32::*;
-	pub use memory_units_crate::{Bytes, ByteSize, RoundUpTo, size_of};
+    pub use memory_units_crate::wasm32::*;
+    pub use memory_units_crate::{size_of, ByteSize, Bytes, RoundUpTo};
 }
 
 /// Deserialized module prepared for instantiation.
 pub struct Module {
-	labels: HashMap<usize, HashMap<usize, usize>>,
-	module: parity_wasm::elements::Module,
+    code_map: Vec<isa::Instructions>,
+    module: parity_wasm::elements::Module,
 }
 
 impl Module {
-	/// Create `Module` from `parity_wasm::elements::Module`.
-	///
-	/// This function will load, validate and prepare a `parity_wasm`'s `Module`.
-	///
-	/// # Errors
-	///
-	/// Returns `Err` if provided `Module` is not valid.
-	///
-	/// # Examples
-	///
-	/// ```rust
-	/// extern crate parity_wasm;
-	/// extern crate wasmi;
-	///
-	/// use parity_wasm::builder;
-	/// use parity_wasm::elements;
-	///
-	/// fn main() {
-	///     let parity_module =
-	///         builder::module()
-	///             .function()
-	///                 .signature().with_param(elements::ValueType::I32).build()
-	///                 .body().build()
-	///             .build()
-	///         .build();
-	///
-	///     let module = wasmi::Module::from_parity_wasm_module(parity_module)
-	///         .expect("parity-wasm builder generated invalid module!");
-	///
-	///     // Instantiate `module`, etc...
-	/// }
-	/// ```
-	pub fn from_parity_wasm_module(module: parity_wasm::elements::Module) -> Result<Module, Error> {
-		use validation::{validate_module, ValidatedModule};
-		let ValidatedModule {
-			labels,
-			module,
-		} = validate_module(module)?;
+    /// Create `Module` from `parity_wasm::elements::Module`.
+    ///
+    /// This function will load, validate and prepare a `parity_wasm`'s `Module`.
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if provided `Module` is not valid.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// extern crate parity_wasm;
+    /// extern crate wasmi;
+    ///
+    /// use parity_wasm::builder;
+    /// use parity_wasm::elements;
+    ///
+    /// fn main() {
+    ///     let parity_module =
+    ///         builder::module()
+    ///             .function()
+    ///                 .signature().with_param(elements::ValueType::I32).build()
+    ///                 .body().build()
+    ///             .build()
+    ///         .build();
+    ///
+    ///     let module = wasmi::Module::from_parity_wasm_module(parity_module)
+    ///         .expect("parity-wasm builder generated invalid module!");
+    ///
+    ///     // Instantiate `module`, etc...
+    /// }
+    /// ```
+    pub fn from_parity_wasm_module(module: parity_wasm::elements::Module) -> Result<Module, Error> {
+        let prepare::CompiledModule { code_map, module } = prepare::compile_module(module)?;
 
-		Ok(Module {
-			labels,
-			module,
-		})
-	}
+        Ok(Module { code_map, module })
+    }
 
-	/// Fail if the module contains any floating-point operations
-	///
-	/// # Errors
-	///
-	/// Returns `Err` if provided `Module` is not valid.
-	///
-	/// # Examples
-	///
-	/// ```rust
-	/// # extern crate wasmi;
-	/// # extern crate wabt;
-	///
-	/// let wasm_binary: Vec<u8> =
-	///     wabt::wat2wasm(
-	///         r#"
-	///         (module
-	///          (func $add (param $lhs i32) (param $rhs i32) (result i32)
-	///                get_local $lhs
-	///                get_local $rhs
-	///                i32.add))
-	///         "#,
-	///     )
-	///     .expect("failed to parse wat");
-	///
-	/// // Load wasm binary and prepare it for instantiation.
-	/// let module = wasmi::Module::from_buffer(&wasm_binary).expect("Parsing failed");
-	/// assert!(module.deny_floating_point().is_ok());
-	///
-	/// let wasm_binary: Vec<u8> =
-	///     wabt::wat2wasm(
-	///         r#"
-	///         (module
-	///          (func $add (param $lhs f32) (param $rhs f32) (result f32)
-	///                get_local $lhs
-	///                get_local $rhs
-	///                f32.add))
-	///         "#,
-	///     )
-	///     .expect("failed to parse wat");
-	///
-	/// let module = wasmi::Module::from_buffer(&wasm_binary).expect("Parsing failed");
-	/// assert!(module.deny_floating_point().is_err());
-	///
-	/// let wasm_binary: Vec<u8> =
-	///     wabt::wat2wasm(
-	///         r#"
-	///         (module
-	///          (func $add (param $lhs f32) (param $rhs f32) (result f32)
-	///                get_local $lhs))
-	///         "#,
-	///     )
-	///     .expect("failed to parse wat");
-	///
-	/// let module = wasmi::Module::from_buffer(&wasm_binary).expect("Parsing failed");
-	/// assert!(module.deny_floating_point().is_err());
-	/// ```
-	pub fn deny_floating_point(&self) -> Result<(), Error> {
-		validation::deny_floating_point(&self.module).map_err(Into::into)
-	}
+    /// Fail if the module contains any floating-point operations
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if provided `Module` is not valid.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// # extern crate wasmi;
+    /// # extern crate wabt;
+    ///
+    /// let wasm_binary: Vec<u8> =
+    ///     wabt::wat2wasm(
+    ///         r#"
+    ///         (module
+    ///          (func $add (param $lhs i32) (param $rhs i32) (result i32)
+    ///                get_local $lhs
+    ///                get_local $rhs
+    ///                i32.add))
+    ///         "#,
+    ///     )
+    ///     .expect("failed to parse wat");
+    ///
+    /// // Load wasm binary and prepare it for instantiation.
+    /// let module = wasmi::Module::from_buffer(&wasm_binary).expect("Parsing failed");
+    /// assert!(module.deny_floating_point().is_ok());
+    ///
+    /// let wasm_binary: Vec<u8> =
+    ///     wabt::wat2wasm(
+    ///         r#"
+    ///         (module
+    ///          (func $add (param $lhs f32) (param $rhs f32) (result f32)
+    ///                get_local $lhs
+    ///                get_local $rhs
+    ///                f32.add))
+    ///         "#,
+    ///     )
+    ///     .expect("failed to parse wat");
+    ///
+    /// let module = wasmi::Module::from_buffer(&wasm_binary).expect("Parsing failed");
+    /// assert!(module.deny_floating_point().is_err());
+    ///
+    /// let wasm_binary: Vec<u8> =
+    ///     wabt::wat2wasm(
+    ///         r#"
+    ///         (module
+    ///          (func $add (param $lhs f32) (param $rhs f32) (result f32)
+    ///                get_local $lhs))
+    ///         "#,
+    ///     )
+    ///     .expect("failed to parse wat");
+    ///
+    /// let module = wasmi::Module::from_buffer(&wasm_binary).expect("Parsing failed");
+    /// assert!(module.deny_floating_point().is_err());
+    /// ```
+    pub fn deny_floating_point(&self) -> Result<(), Error> {
+        prepare::deny_floating_point(&self.module).map_err(Into::into)
+    }
 
-	/// Create `Module` from a given buffer.
-	///
-	/// This function will deserialize wasm module from a given module,
-	/// validate and prepare it for instantiation.
-	///
-	/// # Errors
-	///
-	/// Returns `Err` if wasm binary in provided `buffer` is not valid wasm binary.
-	///
-	/// # Examples
-	///
-	/// ```rust
-	/// extern crate wasmi;
-	///
-	/// fn main() {
-	///     let module =
-	///         wasmi::Module::from_buffer(
-	///             // Minimal module:
-	///             //   \0asm - magic
-	///             //    0x01 - version (in little-endian)
-	///             &[0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00]
-	///         ).expect("Failed to load minimal module");
-	///
-	///     // Instantiate `module`, etc...
-	/// }
-	/// ```
-	pub fn from_buffer<B: AsRef<[u8]>>(buffer: B) -> Result<Module, Error> {
-		let module = parity_wasm::elements::deserialize_buffer(buffer.as_ref())
-			.map_err(|e: parity_wasm::elements::Error| Error::Validation(e.to_string()))?;
-		Module::from_parity_wasm_module(module)
-	}
+    /// Create `Module` from a given buffer.
+    ///
+    /// This function will deserialize wasm module from a given module,
+    /// validate and prepare it for instantiation.
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if wasm binary in provided `buffer` is not valid wasm binary.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// extern crate wasmi;
+    ///
+    /// fn main() {
+    ///     let module =
+    ///         wasmi::Module::from_buffer(
+    ///             // Minimal module:
+    ///             //   \0asm - magic
+    ///             //    0x01 - version (in little-endian)
+    ///             &[0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00]
+    ///         ).expect("Failed to load minimal module");
+    ///
+    ///     // Instantiate `module`, etc...
+    /// }
+    /// ```
+    pub fn from_buffer<B: AsRef<[u8]>>(buffer: B) -> Result<Module, Error> {
+        let module = parity_wasm::elements::deserialize_buffer(buffer.as_ref())
+            .map_err(|e: parity_wasm::elements::Error| Error::Validation(e.to_string()))?;
+        Module::from_parity_wasm_module(module)
+    }
 
-	pub(crate) fn module(&self) -> &parity_wasm::elements::Module {
-		&self.module
-	}
+    pub(crate) fn module(&self) -> &parity_wasm::elements::Module {
+        &self.module
+    }
 
-	pub(crate) fn labels(&self) -> &HashMap<usize, HashMap<usize, usize>> {
-		&self.labels
-	}
+    pub(crate) fn code(&self) -> &Vec<isa::Instructions> {
+        &self.code_map
+    }
 }

src/memory.rs

@@ -1,539 +0,0 @@
-use std::u32;
-use std::ops::Range;
-use std::cmp;
-use std::fmt;
-use std::rc::Rc;
-use std::cell::RefCell;
-use parity_wasm::elements::ResizableLimits;
-use Error;
-use memory_units::{RoundUpTo, Pages, Bytes};
-
-/// Size of a page of [linear memory][`MemoryInstance`] - 64KiB.
-///
-/// The size of a memory is always a integer multiple of a page size.
-///
-/// [`MemoryInstance`]: struct.MemoryInstance.html
-pub const LINEAR_MEMORY_PAGE_SIZE: Bytes = Bytes(65536);
-
-/// Maximal number of pages.
-const LINEAR_MEMORY_MAX_PAGES: Pages = Pages(65536);
-
-/// Reference to a memory (See [`MemoryInstance`] for details).
-///
-/// This reference has a reference-counting semantics.
-///
-/// [`MemoryInstance`]: struct.MemoryInstance.html
-///
-#[derive(Clone, Debug)]
-pub struct MemoryRef(Rc<MemoryInstance>);
-
-impl ::std::ops::Deref for MemoryRef {
-	type Target = MemoryInstance;
-	fn deref(&self) -> &MemoryInstance {
-		&self.0
-	}
-}
-
-/// Runtime representation of a linear memory (or `memory` for short).
-///
-/// A memory is a contiguous, mutable array of raw bytes. Wasm code can load and store values
-/// from/to a linear memory at any byte address.
-/// A trap occurs if an access is not within the bounds of the current memory size.
-///
-/// A memory is created with an initial size but can be grown dynamically.
-/// The growth can be limited by specifying maximum size.
-/// The size of a memory is always a integer multiple of a [page size][`LINEAR_MEMORY_PAGE_SIZE`] - 64KiB.
-///
-/// At the moment, wasm doesn't provide any way to shrink the memory.
-///
-/// [`LINEAR_MEMORY_PAGE_SIZE`]: constant.LINEAR_MEMORY_PAGE_SIZE.html
-pub struct MemoryInstance {
-	/// Memory limits.
-	limits: ResizableLimits,
-	/// Linear memory buffer.
-	buffer: RefCell<Vec<u8>>,
-	initial: Pages,
-	maximum: Option<Pages>,
-}
-
-impl fmt::Debug for MemoryInstance {
-	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-		f.debug_struct("MemoryInstance")
-			.field("limits", &self.limits)
-			.field("buffer.len", &self.buffer.borrow().len())
-			.field("maximum", &self.maximum)
-			.field("initial", &self.initial)
-			.finish()
-	}
-}
-
-struct CheckedRegion<'a, B: 'a> where B: ::std::ops::Deref<Target=Vec<u8>> {
-	buffer: &'a B,
-	offset: usize,
-	size: usize,
-}
-
-impl<'a, B: 'a> CheckedRegion<'a, B> where B: ::std::ops::Deref<Target=Vec<u8>> {
-	fn range(&self) -> Range<usize> {
-		self.offset..self.offset+self.size
-	}
-
-	fn slice(&self) -> &[u8] {
-		&self.buffer[self.range()]
-	}
-
-	fn intersects(&self, other: &Self) -> bool {
-		let low = cmp::max(self.offset, other.offset);
-		let high = cmp::min(self.offset + self.size, other.offset + other.size);
-
-		low < high
-	}
-}
-
-impl MemoryInstance {
-	/// Allocate a memory instance.
-	///
-	/// The memory allocated with initial number of pages specified by `initial`.
-	/// Minimal possible value for `initial` is 0 and maximum possible is `65536`.
-	/// (Since maximum addressible memory is 2<sup>32</sup> = 4GiB = 65536 * [64KiB][`LINEAR_MEMORY_PAGE_SIZE`]).
-	///
-	/// It is possible to limit maximum number of pages this memory instance can have by specifying
-	/// `maximum`. If not specified, this memory instance would be able to allocate up to 4GiB.
-	///
-	/// Allocated memory is always zeroed.
-	///
-	/// # Errors
-	///
-	/// Returns `Err` if:
-	///
-	/// - `initial` is greater than `maximum`
-	/// - either `initial` or `maximum` is greater than `65536`.
-	///
-	/// [`LINEAR_MEMORY_PAGE_SIZE`]: constant.LINEAR_MEMORY_PAGE_SIZE.html
-	pub fn alloc(initial: Pages, maximum: Option<Pages>) -> Result<MemoryRef, Error> {
-		validate_memory(initial, maximum).map_err(Error::Memory)?;
-
-		let memory = MemoryInstance::new(initial, maximum);
-		Ok(MemoryRef(Rc::new(memory)))
-	}
-
-	/// Create new linear memory instance.
-	fn new(initial: Pages, maximum: Option<Pages>) -> Self {
-		let limits = ResizableLimits::new(initial.0 as u32, maximum.map(|p| p.0 as u32));
-
-		let initial_size: Bytes = initial.into();
-		MemoryInstance {
-			limits: limits,
-			buffer: RefCell::new(vec![0; initial_size.0]),
-			initial: initial,
-			maximum: maximum,
-		}
-	}
-
-	/// Return linear memory limits.
-	pub(crate) fn limits(&self) -> &ResizableLimits {
-		&self.limits
-	}
-
-	/// Returns number of pages this `MemoryInstance` was created with.
-	pub fn initial(&self) -> Pages {
-		self.initial
-	}
-
-	/// Returns maximum amount of pages this `MemoryInstance` can grow to.
-	///
-	/// Returns `None` if there is no limit set.
-	/// Maximum memory size cannot exceed `65536` pages or 4GiB.
-	pub fn maximum(&self) -> Option<Pages> {
-		self.maximum
-	}
-
-	/// Returns current linear memory size.
-	///
-	/// Maximum memory size cannot exceed `65536` pages or 4GiB.
-	///
-	/// # Example
-	///
-	/// To convert number of pages to number of bytes you can use the following code:
-	///
-	/// ```rust
-	/// use wasmi::MemoryInstance;
-	/// use wasmi::memory_units::*;
-	///
-	/// let memory = MemoryInstance::alloc(Pages(1), None).unwrap();
-	/// let byte_size: Bytes = memory.current_size().into();
-	/// assert_eq!(
-	///     byte_size,
-	///     Bytes(65536),
-	/// );
-	/// ```
-	pub fn current_size(&self) -> Pages {
-		Bytes(self.buffer.borrow().len()).round_up_to()
-	}
-
-	/// Copy data from memory at given offset.
-	///
-	/// This will allocate vector for you.
-	/// If you can provide a mutable slice you can use [`get_into`].
-	///
-	/// [`get_into`]: #method.get_into
-	pub fn get(&self, offset: u32, size: usize) -> Result<Vec<u8>, Error> {
-		let buffer = self.buffer.borrow();
-		let region = self.checked_region(&buffer, offset as usize, size)?;
-
-		Ok(region.slice().to_vec())
-	}
-
-	/// Copy data from given offset in the memory into `target` slice.
-	///
-	/// # Errors
-	///
-	/// Returns `Err` if the specified region is out of bounds.
-	pub fn get_into(&self, offset: u32, target: &mut [u8]) -> Result<(), Error> {
-		let buffer = self.buffer.borrow();
-		let region = self.checked_region(&buffer, offset as usize, target.len())?;
-
-		target.copy_from_slice(region.slice());
-
-		Ok(())
-	}
-
-	/// Copy data in the memory at given offset.
-	pub fn set(&self, offset: u32, value: &[u8]) -> Result<(), Error> {
-		let mut buffer = self.buffer.borrow_mut();
-		let range = self.checked_region(&buffer, offset as usize, value.len())?.range();
-
-		buffer[range].copy_from_slice(value);
-
-		Ok(())
-	}
-
-	/// Increases the size of the linear memory by given number of pages.
-	/// Returns previous memory size if succeeds.
-	///
-	/// # Errors
-	///
-	/// Returns `Err` if attempted to allocate more memory than permited by the limit.
-	pub fn grow(&self, additional: Pages) -> Result<Pages, Error> {
-		let size_before_grow: Pages = self.current_size();
-
-		if additional == Pages(0) {
-			return Ok(size_before_grow);
-		}
-		if additional > Pages(65536) {
-			return Err(Error::Memory(format!(
-				"Trying to grow memory by more than 65536 pages"
-			)));
-		}
-
-		let new_size: Pages = size_before_grow + additional;
-		let maximum = self.maximum.unwrap_or(LINEAR_MEMORY_MAX_PAGES);
-		if new_size > maximum {
-			return Err(Error::Memory(format!(
-				"Trying to grow memory by {} pages when already have {}",
-				additional.0, size_before_grow.0,
-			)));
-		}
-
-		// Resize underlying buffer up to a new size filling newly allocated space with zeroes.
-		// This size is guaranteed to be larger than current size.
-		let new_buffer_length: Bytes = new_size.into();
-		{
-			let mut buffer = self.buffer.borrow_mut();
-			debug_assert!(new_buffer_length.0 > buffer.len());
-			buffer.resize(new_buffer_length.0, 0);
-		}
-		Ok(size_before_grow)
-	}
-
-	fn checked_region<'a, B>(&self, buffer: &'a B, offset: usize, size: usize) -> Result<CheckedRegion<'a, B>, Error>
-		where B: ::std::ops::Deref<Target=Vec<u8>>
-	{
-		let end = offset.checked_add(size)
-			.ok_or_else(|| Error::Memory(format!("trying to access memory block of size {} from offset {}", size, offset)))?;
-
-		if end > buffer.len() {
-			return Err(Error::Memory(format!("trying to access region [{}..{}] in memory [0..{}]", offset, end, buffer.len())));
-		}
-
-		Ok(CheckedRegion {
-			buffer: buffer,
-			offset: offset,
-			size: size,
-		})
-	}
-
-	/// Copy contents of one memory region to another.
-	///
-	/// Semantically equivalent to `memmove`.
-	///
-	/// # Errors
-	///
-	/// Returns `Err` if either of specified regions is out of bounds.
-	pub fn copy(&self, src_offset: usize, dst_offset: usize, len: usize) -> Result<(), Error> {
-		let buffer = self.buffer.borrow_mut();
-
-		let read_region = self.checked_region(&buffer, src_offset, len)?;
-		let write_region = self.checked_region(&buffer, dst_offset, len)?;
-
-		unsafe { ::std::ptr::copy(
-			buffer[read_region.range()].as_ptr(),
-			buffer[write_region.range()].as_ptr() as *mut _,
-			len,
-		)}
-
-		Ok(())
-	}
-
-	/// Copy contents of one memory region to another (non-overlapping version).
-	///
-	/// Semantically equivalent to `memcpy`.
-	/// but returns Error if source overlaping with destination.
-	///
-	/// # Errors
-	///
-	/// Returns `Err` if:
-	///
-	/// - either of specified regions is out of bounds,
-	/// - these regions overlaps.
-	pub fn copy_nonoverlapping(&self, src_offset: usize, dst_offset: usize, len: usize) -> Result<(), Error> {
-		let buffer = self.buffer.borrow_mut();
-
-		let read_region = self.checked_region(&buffer, src_offset, len)?;
-		let write_region = self.checked_region(&buffer, dst_offset, len)?;
-
-		if read_region.intersects(&write_region) {
-			return Err(Error::Memory(format!("non-overlapping copy is used for overlapping regions")))
-		}
-
-		unsafe { ::std::ptr::copy_nonoverlapping(
-			buffer[read_region.range()].as_ptr(),
-			buffer[write_region.range()].as_ptr() as *mut _,
-			len,
-		)}
-
-		Ok(())
-	}
-
-	/// Fill the memory region with the specified value.
-	///
-	/// Semantically equivalent to `memset`.
-	///
-	/// # Errors
-	///
-	/// Returns `Err` if the specified region is out of bounds.
-	pub fn clear(&self, offset: usize, new_val: u8, len: usize) -> Result<(), Error> {
-		let mut buffer = self.buffer.borrow_mut();
-
-		let range = self.checked_region(&buffer, offset, len)?.range();
-		for val in &mut buffer[range] { *val = new_val }
-		Ok(())
-	}
-
-	/// Fill the specified memory region with zeroes.
-	///
-	/// # Errors
-	///
-	/// Returns `Err` if the specified region is out of bounds.
-	pub fn zero(&self, offset: usize, len: usize) -> Result<(), Error> {
-		self.clear(offset, 0, len)
-	}
-
-	/// Provides direct access to the underlying memory buffer.
-	///
-	/// # Panics
-	///
-	/// Any call that requires write access to memory (such as [`set`], [`clear`], etc) made within
-	/// the closure will panic. Proceed with caution.
-	///
-	/// [`set`]: #method.get
-	/// [`clear`]: #method.set
-	pub fn with_direct_access<R, F: FnOnce(&[u8]) -> R>(&self, f: F) -> R {
-		let buf = self.buffer.borrow();
-		f(&*buf)
-	}
-
-	/// Provides direct mutable access to the underlying memory buffer.
-	///
-	/// # Panics
-	///
-	/// Any calls that requires either read or write access to memory (such as [`get`], [`set`], [`copy`], etc) made
-	/// within the closure will panic. Proceed with caution.
-	///
-	/// [`get`]: #method.get
-	/// [`set`]: #method.set
-	/// [`copy`]: #method.copy
-	pub fn with_direct_access_mut<R, F: FnOnce(&mut [u8]) -> R>(&self, f: F) -> R {
-		let mut buf = self.buffer.borrow_mut();
-		f(&mut *buf)
-	}
-}
-
-pub fn validate_memory(initial: Pages, maximum: Option<Pages>) -> Result<(), String> {
-	if initial > LINEAR_MEMORY_MAX_PAGES {
-		return Err(format!("initial memory size must be at most {} pages", LINEAR_MEMORY_MAX_PAGES.0));
-	}
-	if let Some(maximum) = maximum {
-		if initial > maximum {
-			return Err(format!(
-				"maximum limit {} is less than minimum {}",
-				maximum.0,
-				initial.0,
-			));
-		}
-
-		if maximum > LINEAR_MEMORY_MAX_PAGES {
-			return Err(format!("maximum memory size must be at most {} pages", LINEAR_MEMORY_MAX_PAGES.0));
-		}
-	}
-	Ok(())
-}
-
-#[cfg(test)]
-mod tests {
-
-	use super::{MemoryInstance, LINEAR_MEMORY_PAGE_SIZE};
-	use Error;
-	use memory_units::Pages;
-
-	#[test]
-	fn alloc() {
-		#[cfg(target_pointer_width = "64")]
-		let fixtures = &[
-			(0, None, true),
-			(0, Some(0), true),
-			(1, None, true),
-			(1, Some(1), true),
-			(0, Some(1), true),
-			(1, Some(0), false),
-			(0, Some(65536), true),
-			(65536, Some(65536), true),
-			(65536, Some(0), false),
-			(65536, None, true),
-		];
-
-		#[cfg(target_pointer_width = "32")]
-		let fixtures = &[
-			(0, None, true),
-			(0, Some(0), true),
-			(1, None, true),
-			(1, Some(1), true),
-			(0, Some(1), true),
-			(1, Some(0), false),
-		];
-
-		for (index, &(initial, maybe_max, expected_ok)) in fixtures.iter().enumerate() {
-			let initial: Pages = Pages(initial);
-			let maximum: Option<Pages> = maybe_max.map(|m| Pages(m));
-			let result = MemoryInstance::alloc(initial, maximum);
-			if result.is_ok() != expected_ok {
-				panic!(
-					"unexpected error at {}, initial={:?}, max={:?}, expected={}, result={:?}",
-					index,
-					initial,
-					maybe_max,
-					expected_ok,
-					result,
-				);
-			}
-		}
-	}
-
-	#[test]
-	fn ensure_page_size() {
-		use memory_units::ByteSize;
-		assert_eq!(LINEAR_MEMORY_PAGE_SIZE, Pages::byte_size());
-	}
-
-	fn create_memory(initial_content: &[u8]) -> MemoryInstance {
-		let mem = MemoryInstance::new(Pages(1), Some(Pages(1)));
-		mem.set(0, initial_content).expect("Successful initialize the memory");
-		mem
-	}
-
-	#[test]
-	fn copy_overlaps_1() {
-		let mem = create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
-		mem.copy(0, 4, 6).expect("Successfully copy the elements");
-		let result = mem.get(0, 10).expect("Successfully retrieve the result");
-		assert_eq!(result, &[0, 1, 2, 3, 0, 1, 2, 3, 4, 5]);
-	}
-
-	#[test]
-	fn copy_overlaps_2() {
-		let mem = create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
-		mem.copy(4, 0, 6).expect("Successfully copy the elements");
-		let result = mem.get(0, 10).expect("Successfully retrieve the result");
-		assert_eq!(result, &[4, 5, 6, 7, 8, 9, 6, 7, 8, 9]);
-	}
-
-	#[test]
-	fn copy_nonoverlapping() {
-		let mem = create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
-		mem.copy_nonoverlapping(0, 10, 10).expect("Successfully copy the elements");
-		let result = mem.get(10, 10).expect("Successfully retrieve the result");
-		assert_eq!(result, &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
-	}
-
-	#[test]
-	fn copy_nonoverlapping_overlaps_1() {
-		let mem = create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
-		let result = mem.copy_nonoverlapping(0, 4, 6);
-		match result {
-			Err(Error::Memory(_)) => {},
-			_ => panic!("Expected Error::Memory(_) result, but got {:?}", result),
-		}
-	}
-
-	#[test]
-	fn copy_nonoverlapping_overlaps_2() {
-		let mem = create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
-		let result = mem.copy_nonoverlapping(4, 0, 6);
-		match result {
-			Err(Error::Memory(_)) => {},
-			_ => panic!("Expected Error::Memory(_), but got {:?}", result),
-		}
-	}
-
-	#[test]
-	fn clear() {
-		let mem = create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
-		mem.clear(0, 0x4A, 10).expect("To successfully clear the memory");
-		let result = mem.get(0, 10).expect("To successfully retrieve the result");
-		assert_eq!(result, &[0x4A; 10]);
-	}
-
-	#[test]
-	fn get_into() {
-		let mem = MemoryInstance::new(Pages(1), None);
-		mem.set(6, &[13, 17, 129]).expect("memory set should not fail");
-
-		let mut data = [0u8; 2];
-		mem.get_into(7, &mut data[..]).expect("get_into should not fail");
-
-		assert_eq!(data, [17, 129]);
-	}
-
-	#[test]
-	fn zero_copy() {
-		let mem = MemoryInstance::alloc(Pages(1), None).unwrap();
-		mem.with_direct_access_mut(|buf| {
-			assert_eq!(buf.len(), 65536);
-			buf[..10].copy_from_slice(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
-		});
-		mem.with_direct_access(|buf| {
-			assert_eq!(buf.len(), 65536);
-			assert_eq!(&buf[..10], &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
-		});
-	}
-
-	#[should_panic]
-	#[test]
-	fn zero_copy_panics_on_nested_access() {
-		let mem = MemoryInstance::alloc(Pages(1), None).unwrap();
-		let mem_inner = mem.clone();
-		mem.with_direct_access(move |_| {
-			let _ = mem_inner.set(0, &[11, 12, 13]);
-		});
-	}
-}

src/memory/mmap_bytebuf.rs

@@ -0,0 +1,189 @@
+//! An implementation of a `ByteBuf` based on virtual memory.
+//!
+//! This implementation uses `mmap` on POSIX systems (and should use `VirtualAlloc` on windows).
+//! There are possibilities to improve the performance for the reallocating case by reserving
+//! memory up to maximum. This might be a problem for systems that don't have a lot of virtual
+//! memory (i.e. 32-bit platforms).
+
+use std::ptr::{self, NonNull};
+use std::slice;
+
+struct Mmap {
+    /// The pointer that points to the start of the mapping.
+    ///
+    /// This value doesn't change after creation.
+    ptr: NonNull<u8>,
+    /// The length of this mapping.
+    ///
+    /// Cannot be more than `isize::max_value()`. This value doesn't change after creation.
+    len: usize,
+}
+
+impl Mmap {
+    /// Create a new mmap mapping
+    ///
+    /// Returns `Err` if:
+    /// - `len` should not exceed `isize::max_value()`
+    /// - `len` should be greater than 0.
+    /// - `mmap` returns an error (almost certainly means out of memory).
+    fn new(len: usize) -> Result<Self, &'static str> {
+        if len > isize::max_value() as usize {
+            return Err("`len` should not exceed `isize::max_value()`");
+        }
+        if len == 0 {
+            return Err("`len` should be greater than 0");
+        }
+
+        let ptr_or_err = unsafe {
+            // Safety Proof:
+            // There are not specific safety proofs are required for this call, since the call
+            // by itself can't invoke any safety problems (however, misusing its result can).
+            libc::mmap(
+                // `addr` - let the system to choose the address at which to create the mapping.
+                ptr::null_mut(),
+                // the length of the mapping in bytes.
+                len,
+                // `prot` - protection flags: READ WRITE !EXECUTE
+                libc::PROT_READ | libc::PROT_WRITE,
+                // `flags`
+                // `MAP_ANON` - mapping is not backed by any file and initial contents are
+                // initialized to zero.
+                // `MAP_PRIVATE` - the mapping is private to this process.
+                libc::MAP_ANON | libc::MAP_PRIVATE,
+                // `fildes` - a file descriptor. Pass -1 as this is required for some platforms
+                // when the `MAP_ANON` is passed.
+                -1,
+                // `offset` - offset from the file.
+                0,
+            )
+        };
+
+        match ptr_or_err {
+            // With the current parameters, the error can only be returned in case of insufficient
+            // memory.
+            libc::MAP_FAILED => Err("mmap returned an error"),
+            _ => {
+                let ptr = NonNull::new(ptr_or_err as *mut u8).ok_or("mmap returned 0")?;
+                Ok(Self { ptr, len })
+            }
+        }
+    }
+
+    fn as_slice(&self) -> &[u8] {
+        unsafe {
+            // Safety Proof:
+            // - Aliasing guarantees of `self.ptr` are not violated since `self` is the only owner.
+            // - This pointer was allocated for `self.len` bytes and thus is a valid slice.
+            // - `self.len` doesn't change throughout the lifetime of `self`.
+            // - The value is returned valid for the duration of lifetime of `self`.
+            //   `self` cannot be destroyed while the returned slice is alive.
+            // - `self.ptr` is of `NonNull` type and thus `.as_ptr()` can never return NULL.
+            // - `self.len` cannot be larger than `isize::max_value()`.
+            slice::from_raw_parts(self.ptr.as_ptr(), self.len)
+        }
+    }
+
+    fn as_slice_mut(&mut self) -> &mut [u8] {
+        unsafe {
+            // Safety Proof:
+            // - See the proof for `Self::as_slice`
+            // - Additionally, it is not possible to obtain two mutable references for `self.ptr`
+            slice::from_raw_parts_mut(self.ptr.as_ptr(), self.len)
+        }
+    }
+}
+
+impl Drop for Mmap {
+    fn drop(&mut self) {
+        let ret_val = unsafe {
+            // Safety proof:
+            // - `self.ptr` was allocated by a call to `mmap`.
+            // - `self.len` was saved at the same time and it doesn't change throughout the lifetime
+            //   of `self`.
+            libc::munmap(self.ptr.as_ptr() as *mut libc::c_void, self.len)
+        };
+
+        // There is no reason for `munmap` to fail to deallocate a private annonymous mapping
+        // allocated by `mmap`.
+        // However, for the cases when it actually fails prefer to fail, in order to not leak
+        // and exhaust the virtual memory.
+        assert_eq!(ret_val, 0, "munmap failed");
+    }
+}
+
+pub struct ByteBuf {
+    mmap: Option<Mmap>,
+}
+
+impl ByteBuf {
+    pub fn new(len: usize) -> Result<Self, &'static str> {
+        let mmap = if len == 0 {
+            None
+        } else {
+            Some(Mmap::new(len)?)
+        };
+        Ok(Self { mmap })
+    }
+
+    pub fn realloc(&mut self, new_len: usize) -> Result<(), &'static str> {
+        let new_mmap = if new_len == 0 {
+            None
+        } else {
+            let mut new_mmap = Mmap::new(new_len)?;
+            if let Some(cur_mmap) = self.mmap.take() {
+                let src = cur_mmap.as_slice();
+                let dst = new_mmap.as_slice_mut();
+                let amount = src.len().min(dst.len());
+                dst[..amount].copy_from_slice(&src[..amount]);
+            }
+            Some(new_mmap)
+        };
+
+        self.mmap = new_mmap;
+        Ok(())
+    }
+
+    pub fn len(&self) -> usize {
+        self.mmap.as_ref().map(|m| m.len).unwrap_or(0)
+    }
+
+    pub fn as_slice(&self) -> &[u8] {
+        self.mmap.as_ref().map(|m| m.as_slice()).unwrap_or(&[])
+    }
+
+    pub fn as_slice_mut(&mut self) -> &mut [u8] {
+        self.mmap
+            .as_mut()
+            .map(|m| m.as_slice_mut())
+            .unwrap_or(&mut [])
+    }
+
+    pub fn erase(&mut self) -> Result<(), &'static str> {
+        let len = self.len();
+        if len > 0 {
+            // The order is important.
+            //
+            // 1. First we clear, and thus drop, the current mmap if any.
+            // 2. And then we create a new one.
+            //
+            // Otherwise we double the peak memory consumption.
+            self.mmap = None;
+            self.mmap = Some(Mmap::new(len)?);
+        }
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::ByteBuf;
+
+    const PAGE_SIZE: usize = 4096;
+
+    // This is not required since wasm memories can only grow but nice to have.
+    #[test]
+    fn byte_buf_shrink() {
+        let mut byte_buf = ByteBuf::new(PAGE_SIZE * 3).unwrap();
+        byte_buf.realloc(PAGE_SIZE * 2).unwrap();
+    }
+}

src/memory/mod.rs

@@ -0,0 +1,740 @@
+use alloc::{rc::Rc, string::ToString, vec::Vec};
+use core::{
+    cell::{Cell, RefCell},
+    cmp, fmt,
+    ops::Range,
+    u32,
+};
+use memory_units::{Bytes, Pages, RoundUpTo};
+use parity_wasm::elements::ResizableLimits;
+use value::LittleEndianConvert;
+use Error;
+
+#[cfg(all(unix, not(feature = "vec_memory")))]
+#[path = "mmap_bytebuf.rs"]
+mod bytebuf;
+
+#[cfg(any(not(unix), feature = "vec_memory"))]
+#[path = "vec_bytebuf.rs"]
+mod bytebuf;
+
+use self::bytebuf::ByteBuf;
+
+/// Size of a page of [linear memory][`MemoryInstance`] - 64KiB.
+///
+/// The size of a memory is always a integer multiple of a page size.
+///
+/// [`MemoryInstance`]: struct.MemoryInstance.html
+pub const LINEAR_MEMORY_PAGE_SIZE: Bytes = Bytes(65536);
+
+/// Reference to a memory (See [`MemoryInstance`] for details).
+///
+/// This reference has a reference-counting semantics.
+///
+/// [`MemoryInstance`]: struct.MemoryInstance.html
+///
+#[derive(Clone, Debug)]
+pub struct MemoryRef(Rc<MemoryInstance>);
+
+impl ::core::ops::Deref for MemoryRef {
+    type Target = MemoryInstance;
+    fn deref(&self) -> &MemoryInstance {
+        &self.0
+    }
+}
+
+/// Runtime representation of a linear memory (or `memory` for short).
+///
+/// A memory is a contiguous, mutable array of raw bytes. Wasm code can load and store values
+/// from/to a linear memory at any byte address.
+/// A trap occurs if an access is not within the bounds of the current memory size.
+///
+/// A memory is created with an initial size but can be grown dynamically.
+/// The growth can be limited by specifying maximum size.
+/// The size of a memory is always a integer multiple of a [page size][`LINEAR_MEMORY_PAGE_SIZE`] - 64KiB.
+///
+/// At the moment, wasm doesn't provide any way to shrink the memory.
+///
+/// [`LINEAR_MEMORY_PAGE_SIZE`]: constant.LINEAR_MEMORY_PAGE_SIZE.html
+pub struct MemoryInstance {
+    /// Memory limits.
+    limits: ResizableLimits,
+    /// Linear memory buffer with lazy allocation.
+    buffer: RefCell<ByteBuf>,
+    initial: Pages,
+    current_size: Cell<usize>,
+    maximum: Option<Pages>,
+}
+
+impl fmt::Debug for MemoryInstance {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("MemoryInstance")
+            .field("limits", &self.limits)
+            .field("buffer.len", &self.buffer.borrow().len())
+            .field("maximum", &self.maximum)
+            .field("initial", &self.initial)
+            .finish()
+    }
+}
+
+struct CheckedRegion {
+    offset: usize,
+    size: usize,
+}
+
+impl CheckedRegion {
+    fn range(&self) -> Range<usize> {
+        self.offset..self.offset + self.size
+    }
+
+    fn intersects(&self, other: &Self) -> bool {
+        let low = cmp::max(self.offset, other.offset);
+        let high = cmp::min(self.offset + self.size, other.offset + other.size);
+
+        low < high
+    }
+}
+
+impl MemoryInstance {
+    /// Allocate a memory instance.
+    ///
+    /// The memory allocated with initial number of pages specified by `initial`.
+    /// Minimal possible value for `initial` is 0 and maximum possible is `65536`.
+    /// (Since maximum addressible memory is 2<sup>32</sup> = 4GiB = 65536 * [64KiB][`LINEAR_MEMORY_PAGE_SIZE`]).
+    ///
+    /// It is possible to limit maximum number of pages this memory instance can have by specifying
+    /// `maximum`. If not specified, this memory instance would be able to allocate up to 4GiB.
+    ///
+    /// Allocated memory is always zeroed.
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if:
+    ///
+    /// - `initial` is greater than `maximum`
+    /// - either `initial` or `maximum` is greater than `65536`.
+    ///
+    /// [`LINEAR_MEMORY_PAGE_SIZE`]: constant.LINEAR_MEMORY_PAGE_SIZE.html
+    pub fn alloc(initial: Pages, maximum: Option<Pages>) -> Result<MemoryRef, Error> {
+        {
+            use core::convert::TryInto;
+            let initial_u32: u32 = initial.0.try_into().map_err(|_| {
+                Error::Memory(format!("initial ({}) can't be coerced to u32", initial.0))
+            })?;
+            let maximum_u32: Option<u32> = match maximum {
+                Some(maximum_pages) => Some(maximum_pages.0.try_into().map_err(|_| {
+                    Error::Memory(format!(
+                        "maximum ({}) can't be coerced to u32",
+                        maximum_pages.0
+                    ))
+                })?),
+                None => None,
+            };
+            validation::validate_memory(initial_u32, maximum_u32).map_err(Error::Memory)?;
+        }
+
+        let memory = MemoryInstance::new(initial, maximum)?;
+        Ok(MemoryRef(Rc::new(memory)))
+    }
+
+    /// Create new linear memory instance.
+    fn new(initial: Pages, maximum: Option<Pages>) -> Result<Self, Error> {
+        let limits = ResizableLimits::new(initial.0 as u32, maximum.map(|p| p.0 as u32));
+
+        let initial_size: Bytes = initial.into();
+        Ok(MemoryInstance {
+            limits: limits,
+            buffer: RefCell::new(
+                ByteBuf::new(initial_size.0).map_err(|err| Error::Memory(err.to_string()))?,
+            ),
+            initial: initial,
+            current_size: Cell::new(initial_size.0),
+            maximum: maximum,
+        })
+    }
+
+    /// Return linear memory limits.
+    pub(crate) fn limits(&self) -> &ResizableLimits {
+        &self.limits
+    }
+
+    /// Returns number of pages this `MemoryInstance` was created with.
+    pub fn initial(&self) -> Pages {
+        self.initial
+    }
+
+    /// Returns maximum amount of pages this `MemoryInstance` can grow to.
+    ///
+    /// Returns `None` if there is no limit set.
+    /// Maximum memory size cannot exceed `65536` pages or 4GiB.
+    pub fn maximum(&self) -> Option<Pages> {
+        self.maximum
+    }
+
+    /// Returns current linear memory size.
+    ///
+    /// Maximum memory size cannot exceed `65536` pages or 4GiB.
+    ///
+    /// # Example
+    ///
+    /// To convert number of pages to number of bytes you can use the following code:
+    ///
+    /// ```rust
+    /// use wasmi::MemoryInstance;
+    /// use wasmi::memory_units::*;
+    ///
+    /// let memory = MemoryInstance::alloc(Pages(1), None).unwrap();
+    /// let byte_size: Bytes = memory.current_size().into();
+    /// assert_eq!(
+    ///     byte_size,
+    ///     Bytes(65536),
+    /// );
+    /// ```
+    pub fn current_size(&self) -> Pages {
+        Bytes(self.buffer.borrow().len()).round_up_to()
+    }
+
+    /// Get value from memory at given offset.
+    pub fn get_value<T: LittleEndianConvert>(&self, offset: u32) -> Result<T, Error> {
+        let mut buffer = self.buffer.borrow_mut();
+        let region =
+            self.checked_region(&mut buffer, offset as usize, ::core::mem::size_of::<T>())?;
+        Ok(
+            T::from_little_endian(&buffer.as_slice_mut()[region.range()])
+                .expect("Slice size is checked"),
+        )
+    }
+
+    /// Copy data from memory at given offset.
+    ///
+    /// This will allocate vector for you.
+    /// If you can provide a mutable slice you can use [`get_into`].
+    ///
+    /// [`get_into`]: #method.get_into
+    pub fn get(&self, offset: u32, size: usize) -> Result<Vec<u8>, Error> {
+        let mut buffer = self.buffer.borrow_mut();
+        let region = self.checked_region(&mut buffer, offset as usize, size)?;
+
+        Ok(buffer.as_slice_mut()[region.range()].to_vec())
+    }
+
+    /// Copy data from given offset in the memory into `target` slice.
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if the specified region is out of bounds.
+    pub fn get_into(&self, offset: u32, target: &mut [u8]) -> Result<(), Error> {
+        let mut buffer = self.buffer.borrow_mut();
+        let region = self.checked_region(&mut buffer, offset as usize, target.len())?;
+
+        target.copy_from_slice(&buffer.as_slice_mut()[region.range()]);
+
+        Ok(())
+    }
+
+    /// Copy data in the memory at given offset.
+    pub fn set(&self, offset: u32, value: &[u8]) -> Result<(), Error> {
+        let mut buffer = self.buffer.borrow_mut();
+        let range = self
+            .checked_region(&mut buffer, offset as usize, value.len())?
+            .range();
+
+        buffer.as_slice_mut()[range].copy_from_slice(value);
+
+        Ok(())
+    }
+
+    /// Copy value in the memory at given offset.
+    pub fn set_value<T: LittleEndianConvert>(&self, offset: u32, value: T) -> Result<(), Error> {
+        let mut buffer = self.buffer.borrow_mut();
+        let range = self
+            .checked_region(&mut buffer, offset as usize, ::core::mem::size_of::<T>())?
+            .range();
+        value.into_little_endian(&mut buffer.as_slice_mut()[range]);
+        Ok(())
+    }
+
+    /// Increases the size of the linear memory by given number of pages.
+    /// Returns previous memory size if succeeds.
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if attempted to allocate more memory than permited by the limit.
+    pub fn grow(&self, additional: Pages) -> Result<Pages, Error> {
+        let size_before_grow: Pages = self.current_size();
+
+        if additional == Pages(0) {
+            return Ok(size_before_grow);
+        }
+        if additional > Pages(65536) {
+            return Err(Error::Memory(format!(
+                "Trying to grow memory by more than 65536 pages"
+            )));
+        }
+
+        let new_size: Pages = size_before_grow + additional;
+        let maximum = self
+            .maximum
+            .unwrap_or(Pages(validation::LINEAR_MEMORY_MAX_PAGES as usize));
+        if new_size > maximum {
+            return Err(Error::Memory(format!(
+                "Trying to grow memory by {} pages when already have {}",
+                additional.0, size_before_grow.0,
+            )));
+        }
+
+        let new_buffer_length: Bytes = new_size.into();
+        self.buffer
+            .borrow_mut()
+            .realloc(new_buffer_length.0)
+            .map_err(|err| Error::Memory(err.to_string()))?;
+
+        self.current_size.set(new_buffer_length.0);
+
+        Ok(size_before_grow)
+    }
+
+    fn checked_region(
+        &self,
+        buffer: &mut ByteBuf,
+        offset: usize,
+        size: usize,
+    ) -> Result<CheckedRegion, Error> {
+        let end = offset.checked_add(size).ok_or_else(|| {
+            Error::Memory(format!(
+                "trying to access memory block of size {} from offset {}",
+                size, offset
+            ))
+        })?;
+
+        if end > buffer.len() {
+            return Err(Error::Memory(format!(
+                "trying to access region [{}..{}] in memory [0..{}]",
+                offset,
+                end,
+                buffer.len()
+            )));
+        }
+
+        Ok(CheckedRegion {
+            offset: offset,
+            size: size,
+        })
+    }
+
+    fn checked_region_pair(
+        &self,
+        buffer: &mut ByteBuf,
+        offset1: usize,
+        size1: usize,
+        offset2: usize,
+        size2: usize,
+    ) -> Result<(CheckedRegion, CheckedRegion), Error> {
+        let end1 = offset1.checked_add(size1).ok_or_else(|| {
+            Error::Memory(format!(
+                "trying to access memory block of size {} from offset {}",
+                size1, offset1
+            ))
+        })?;
+
+        let end2 = offset2.checked_add(size2).ok_or_else(|| {
+            Error::Memory(format!(
+                "trying to access memory block of size {} from offset {}",
+                size2, offset2
+            ))
+        })?;
+
+        if end1 > buffer.len() {
+            return Err(Error::Memory(format!(
+                "trying to access region [{}..{}] in memory [0..{}]",
+                offset1,
+                end1,
+                buffer.len()
+            )));
+        }
+
+        if end2 > buffer.len() {
+            return Err(Error::Memory(format!(
+                "trying to access region [{}..{}] in memory [0..{}]",
+                offset2,
+                end2,
+                buffer.len()
+            )));
+        }
+
+        Ok((
+            CheckedRegion {
+                offset: offset1,
+                size: size1,
+            },
+            CheckedRegion {
+                offset: offset2,
+                size: size2,
+            },
+        ))
+    }
+
+    /// Copy contents of one memory region to another.
+    ///
+    /// Semantically equivalent to `memmove`.
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if either of specified regions is out of bounds.
+    pub fn copy(&self, src_offset: usize, dst_offset: usize, len: usize) -> Result<(), Error> {
+        let mut buffer = self.buffer.borrow_mut();
+
+        let (read_region, write_region) =
+            self.checked_region_pair(&mut buffer, src_offset, len, dst_offset, len)?;
+
+        unsafe {
+            ::core::ptr::copy(
+                buffer.as_slice()[read_region.range()].as_ptr(),
+                buffer.as_slice_mut()[write_region.range()].as_mut_ptr(),
+                len,
+            )
+        }
+
+        Ok(())
+    }
+
+    /// Copy contents of one memory region to another (non-overlapping version).
+    ///
+    /// Semantically equivalent to `memcpy`.
+    /// but returns Error if source overlaping with destination.
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if:
+    ///
+    /// - either of specified regions is out of bounds,
+    /// - these regions overlaps.
+    pub fn copy_nonoverlapping(
+        &self,
+        src_offset: usize,
+        dst_offset: usize,
+        len: usize,
+    ) -> Result<(), Error> {
+        let mut buffer = self.buffer.borrow_mut();
+
+        let (read_region, write_region) =
+            self.checked_region_pair(&mut buffer, src_offset, len, dst_offset, len)?;
+
+        if read_region.intersects(&write_region) {
+            return Err(Error::Memory(format!(
+                "non-overlapping copy is used for overlapping regions"
+            )));
+        }
+
+        unsafe {
+            ::core::ptr::copy_nonoverlapping(
+                buffer.as_slice()[read_region.range()].as_ptr(),
+                buffer.as_slice_mut()[write_region.range()].as_mut_ptr(),
+                len,
+            )
+        }
+
+        Ok(())
+    }
+
+    /// Copy memory between two (possibly distinct) memory instances.
+    ///
+    /// If the same memory instance passed as `src` and `dst` then usual `copy` will be used.
+    pub fn transfer(
+        src: &MemoryRef,
+        src_offset: usize,
+        dst: &MemoryRef,
+        dst_offset: usize,
+        len: usize,
+    ) -> Result<(), Error> {
+        if Rc::ptr_eq(&src.0, &dst.0) {
+            // `transfer` is invoked with with same source and destination. Let's assume that regions may
+            // overlap and use `copy`.
+            return src.copy(src_offset, dst_offset, len);
+        }
+
+        // Because memory references point to different memory instances, it is safe to `borrow_mut`
+        // both buffers at once (modulo `with_direct_access_mut`).
+        let mut src_buffer = src.buffer.borrow_mut();
+        let mut dst_buffer = dst.buffer.borrow_mut();
+
+        let src_range = src
+            .checked_region(&mut src_buffer, src_offset, len)?
+            .range();
+        let dst_range = dst
+            .checked_region(&mut dst_buffer, dst_offset, len)?
+            .range();
+
+        dst_buffer.as_slice_mut()[dst_range].copy_from_slice(&src_buffer.as_slice()[src_range]);
+
+        Ok(())
+    }
+
+    /// Fill the memory region with the specified value.
+    ///
+    /// Semantically equivalent to `memset`.
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if the specified region is out of bounds.
+    pub fn clear(&self, offset: usize, new_val: u8, len: usize) -> Result<(), Error> {
+        let mut buffer = self.buffer.borrow_mut();
+
+        let range = self.checked_region(&mut buffer, offset, len)?.range();
+
+        for val in &mut buffer.as_slice_mut()[range] {
+            *val = new_val
+        }
+        Ok(())
+    }
+
+    /// Fill the specified memory region with zeroes.
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if the specified region is out of bounds.
+    pub fn zero(&self, offset: usize, len: usize) -> Result<(), Error> {
+        self.clear(offset, 0, len)
+    }
+
+    /// Set every byte in the entire linear memory to 0, preserving its size.
+    ///
+    /// Might be useful for some optimization shenanigans.
+    pub fn erase(&self) -> Result<(), Error> {
+        self.buffer
+            .borrow_mut()
+            .erase()
+            .map_err(|err| Error::Memory(err.to_string()))
+    }
+
+    /// Provides direct access to the underlying memory buffer.
+    ///
+    /// # Panics
+    ///
+    /// Any call that requires write access to memory (such as [`set`], [`clear`], etc) made within
+    /// the closure will panic.
+    ///
+    /// [`set`]: #method.get
+    /// [`clear`]: #method.set
+    pub fn with_direct_access<R, F: FnOnce(&[u8]) -> R>(&self, f: F) -> R {
+        let buf = self.buffer.borrow();
+        f(buf.as_slice())
+    }
+
+    /// Provides direct mutable access to the underlying memory buffer.
+    ///
+    /// # Panics
+    ///
+    /// Any calls that requires either read or write access to memory (such as [`get`], [`set`], [`copy`], etc) made
+    /// within the closure will panic. Proceed with caution.
+    ///
+    /// [`get`]: #method.get
+    /// [`set`]: #method.set
+    pub fn with_direct_access_mut<R, F: FnOnce(&mut [u8]) -> R>(&self, f: F) -> R {
+        let mut buf = self.buffer.borrow_mut();
+        f(buf.as_slice_mut())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+
+    use super::{MemoryInstance, MemoryRef, LINEAR_MEMORY_PAGE_SIZE};
+    use memory_units::Pages;
+    use std::rc::Rc;
+    use Error;
+
+    #[test]
+    fn alloc() {
+        let mut fixtures = vec![
+            (0, None, true),
+            (0, Some(0), true),
+            (1, None, true),
+            (1, Some(1), true),
+            (0, Some(1), true),
+            (1, Some(0), false),
+        ];
+
+        #[cfg(target_pointer_width = "64")]
+        fixtures.extend(&[
+            (65536, Some(65536), true),
+            (65536, Some(0), false),
+            (65536, None, true),
+        ]);
+
+        for (index, &(initial, maybe_max, expected_ok)) in fixtures.iter().enumerate() {
+            let initial: Pages = Pages(initial);
+            let maximum: Option<Pages> = maybe_max.map(|m| Pages(m));
+            let result = MemoryInstance::alloc(initial, maximum);
+            if result.is_ok() != expected_ok {
+                panic!(
+                    "unexpected error at {}, initial={:?}, max={:?}, expected={}, result={:?}",
+                    index, initial, maybe_max, expected_ok, result,
+                );
+            }
+        }
+    }
+
+    #[test]
+    fn ensure_page_size() {
+        use memory_units::ByteSize;
+        assert_eq!(LINEAR_MEMORY_PAGE_SIZE, Pages::byte_size());
+    }
+
+    fn create_memory(initial_content: &[u8]) -> MemoryInstance {
+        let mem = MemoryInstance::new(Pages(1), Some(Pages(1))).unwrap();
+        mem.set(0, initial_content)
+            .expect("Successful initialize the memory");
+        mem
+    }
+
+    #[test]
+    fn copy_overlaps_1() {
+        let mem = create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+        mem.copy(0, 4, 6).expect("Successfully copy the elements");
+        let result = mem.get(0, 10).expect("Successfully retrieve the result");
+        assert_eq!(result, &[0, 1, 2, 3, 0, 1, 2, 3, 4, 5]);
+    }
+
+    #[test]
+    fn copy_overlaps_2() {
+        let mem = create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+        mem.copy(4, 0, 6).expect("Successfully copy the elements");
+        let result = mem.get(0, 10).expect("Successfully retrieve the result");
+        assert_eq!(result, &[4, 5, 6, 7, 8, 9, 6, 7, 8, 9]);
+    }
+
+    #[test]
+    fn copy_nonoverlapping() {
+        let mem = create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+        mem.copy_nonoverlapping(0, 10, 10)
+            .expect("Successfully copy the elements");
+        let result = mem.get(10, 10).expect("Successfully retrieve the result");
+        assert_eq!(result, &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+    }
+
+    #[test]
+    fn copy_nonoverlapping_overlaps_1() {
+        let mem = create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+        let result = mem.copy_nonoverlapping(0, 4, 6);
+        match result {
+            Err(Error::Memory(_)) => {}
+            _ => panic!("Expected Error::Memory(_) result, but got {:?}", result),
+        }
+    }
+
+    #[test]
+    fn copy_nonoverlapping_overlaps_2() {
+        let mem = create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+        let result = mem.copy_nonoverlapping(4, 0, 6);
+        match result {
+            Err(Error::Memory(_)) => {}
+            _ => panic!("Expected Error::Memory(_), but got {:?}", result),
+        }
+    }
+
+    #[test]
+    fn transfer_works() {
+        let src = MemoryRef(Rc::new(create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9])));
+        let dst = MemoryRef(Rc::new(create_memory(&[
+            10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
+        ])));
+
+        MemoryInstance::transfer(&src, 4, &dst, 0, 3).unwrap();
+
+        assert_eq!(src.get(0, 10).unwrap(), &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+        assert_eq!(
+            dst.get(0, 10).unwrap(),
+            &[4, 5, 6, 13, 14, 15, 16, 17, 18, 19]
+        );
+    }
+
+    #[test]
+    fn transfer_still_works_with_same_memory() {
+        let src = MemoryRef(Rc::new(create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9])));
+
+        MemoryInstance::transfer(&src, 4, &src, 0, 3).unwrap();
+
+        assert_eq!(src.get(0, 10).unwrap(), &[4, 5, 6, 3, 4, 5, 6, 7, 8, 9]);
+    }
+
+    #[test]
+    fn transfer_oob_with_same_memory_errors() {
+        let src = MemoryRef(Rc::new(create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9])));
+        assert!(MemoryInstance::transfer(&src, 65535, &src, 0, 3).is_err());
+
+        // Check that memories content left untouched
+        assert_eq!(src.get(0, 10).unwrap(), &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+    }
+
+    #[test]
+    fn transfer_oob_errors() {
+        let src = MemoryRef(Rc::new(create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9])));
+        let dst = MemoryRef(Rc::new(create_memory(&[
+            10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
+        ])));
+
+        assert!(MemoryInstance::transfer(&src, 65535, &dst, 0, 3).is_err());
+
+        // Check that memories content left untouched
+        assert_eq!(src.get(0, 10).unwrap(), &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+        assert_eq!(
+            dst.get(0, 10).unwrap(),
+            &[10, 11, 12, 13, 14, 15, 16, 17, 18, 19]
+        );
+    }
+
+    #[test]
+    fn clear() {
+        let mem = create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+        mem.clear(0, 0x4A, 10)
+            .expect("To successfully clear the memory");
+        let result = mem.get(0, 10).expect("To successfully retrieve the result");
+        assert_eq!(result, &[0x4A; 10]);
+    }
+
+    #[test]
+    fn get_into() {
+        let mem = MemoryInstance::new(Pages(1), None).unwrap();
+        mem.set(6, &[13, 17, 129])
+            .expect("memory set should not fail");
+
+        let mut data = [0u8; 2];
+        mem.get_into(7, &mut data[..])
+            .expect("get_into should not fail");
+
+        assert_eq!(data, [17, 129]);
+    }
+
+    #[test]
+    fn zero_copy() {
+        let mem = MemoryInstance::alloc(Pages(1), None).unwrap();
+        mem.set(100, &[0]).expect("memory set should not fail");
+        mem.with_direct_access_mut(|buf| {
+            assert_eq!(
+                buf.len(),
+                65536,
+                "the buffer length is expected to be 1 page long"
+            );
+            buf[..10].copy_from_slice(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+        });
+        mem.with_direct_access(|buf| {
+            assert_eq!(
+                buf.len(),
+                65536,
+                "the buffer length is expected to be 1 page long"
+            );
+            assert_eq!(&buf[..10], &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+        });
+    }
+
+    #[should_panic]
+    #[test]
+    fn zero_copy_panics_on_nested_access() {
+        let mem = MemoryInstance::alloc(Pages(1), None).unwrap();
+        let mem_inner = mem.clone();
+        mem.with_direct_access(move |_| {
+            let _ = mem_inner.set(0, &[11, 12, 13]);
+        });
+    }
+}

src/memory/vec_bytebuf.rs

@@ -0,0 +1,39 @@
+//! An implementation of `ByteBuf` based on a plain `Vec`.
+
+use alloc::vec::Vec;
+
+pub struct ByteBuf {
+    buf: Vec<u8>,
+}
+
+impl ByteBuf {
+    pub fn new(len: usize) -> Result<Self, &'static str> {
+        let mut buf = Vec::new();
+        buf.resize(len, 0u8);
+        Ok(Self { buf })
+    }
+
+    pub fn realloc(&mut self, new_len: usize) -> Result<(), &'static str> {
+        self.buf.resize(new_len, 0u8);
+        Ok(())
+    }
+
+    pub fn len(&self) -> usize {
+        self.buf.len()
+    }
+
+    pub fn as_slice(&self) -> &[u8] {
+        self.buf.as_ref()
+    }
+
+    pub fn as_slice_mut(&mut self) -> &mut [u8] {
+        self.buf.as_mut()
+    }
+
+    pub fn erase(&mut self) -> Result<(), &'static str> {
+        for v in &mut self.buf {
+            *v = 0;
+        }
+        Ok(())
+    }
+}

src/nan_preserving_float.rs

@@ -0,0 +1,217 @@
+#![allow(missing_docs)]
+
+#[cfg(not(feature = "std"))]
+use libm::{F32Ext, F64Ext};
+
+use core::cmp::{Ordering, PartialEq, PartialOrd};
+use core::ops::{Add, Div, Mul, Neg, Rem, Sub};
+
+macro_rules! impl_binop {
+    ($for:ident, $is:ident, $op:ident, $func_name:ident) => {
+        impl<T: Into<$for>> $op<T> for $for {
+            type Output = Self;
+
+            fn $func_name(self, other: T) -> Self {
+                $for(
+                    $op::$func_name($is::from_bits(self.0), $is::from_bits(other.into().0))
+                        .to_bits(),
+                )
+            }
+        }
+    };
+}
+
+macro_rules! float {
+    ($for:ident, $rep:ident, $is:ident) => {
+        float!(
+            $for,
+            $rep,
+            $is,
+            1 << (::core::mem::size_of::<$is>() * 8 - 1)
+        );
+    };
+    ($for:ident, $rep:ident, $is:ident, $sign_bit:expr) => {
+        #[derive(Copy, Clone)]
+        pub struct $for($rep);
+
+        impl_binop!($for, $is, Add, add);
+        impl_binop!($for, $is, Sub, sub);
+        impl_binop!($for, $is, Mul, mul);
+        impl_binop!($for, $is, Div, div);
+        impl_binop!($for, $is, Rem, rem);
+
+        impl $for {
+            pub fn from_bits(other: $rep) -> Self {
+                $for(other)
+            }
+
+            pub fn to_bits(self) -> $rep {
+                self.0
+            }
+
+            pub fn from_float(fl: $is) -> Self {
+                fl.into()
+            }
+
+            pub fn to_float(self) -> $is {
+                self.into()
+            }
+
+            pub fn is_nan(self) -> bool {
+                self.to_float().is_nan()
+            }
+
+            pub fn abs(self) -> Self {
+                $for(self.0 & !$sign_bit)
+            }
+
+            pub fn fract(self) -> Self {
+                self.to_float().fract().into()
+            }
+
+            pub fn min(self, other: Self) -> Self {
+                Self::from(self.to_float().min(other.to_float()))
+            }
+
+            pub fn max(self, other: Self) -> Self {
+                Self::from(self.to_float().max(other.to_float()))
+            }
+        }
+
+        impl From<$is> for $for {
+            fn from(other: $is) -> $for {
+                $for(other.to_bits())
+            }
+        }
+
+        impl From<$for> for $is {
+            fn from(other: $for) -> $is {
+                <$is>::from_bits(other.0)
+            }
+        }
+
+        impl Neg for $for {
+            type Output = Self;
+
+            fn neg(self) -> Self {
+                $for(self.0 ^ $sign_bit)
+            }
+        }
+
+        impl<T: Into<$for> + Copy> PartialEq<T> for $for {
+            fn eq(&self, other: &T) -> bool {
+                $is::from(*self) == $is::from((*other).into())
+            }
+        }
+
+        impl<T: Into<$for> + Copy> PartialOrd<T> for $for {
+            fn partial_cmp(&self, other: &T) -> Option<Ordering> {
+                $is::from(*self).partial_cmp(&$is::from((*other).into()))
+            }
+        }
+
+        impl ::core::fmt::Debug for $for {
+            fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+                $is::from(*self).fmt(f)
+            }
+        }
+    };
+}
+
+float!(F32, u32, f32);
+float!(F64, u64, f64);
+
+impl From<u32> for F32 {
+    fn from(other: u32) -> Self {
+        Self::from_bits(other)
+    }
+}
+
+impl From<F32> for u32 {
+    fn from(other: F32) -> Self {
+        other.to_bits()
+    }
+}
+
+impl From<u64> for F64 {
+    fn from(other: u64) -> Self {
+        Self::from_bits(other)
+    }
+}
+
+impl From<F64> for u64 {
+    fn from(other: F64) -> Self {
+        other.to_bits()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    extern crate rand;
+
+    use self::rand::Rng;
+
+    use super::{F32, F64};
+
+    use core::{
+        fmt::Debug,
+        iter,
+        ops::{Add, Div, Mul, Neg, Sub},
+    };
+
+    fn test_ops<T, F, I>(iter: I)
+    where
+        T: Add<Output = T>
+            + Div<Output = T>
+            + Mul<Output = T>
+            + Sub<Output = T>
+            + Neg<Output = T>
+            + Copy
+            + Debug
+            + PartialEq,
+        F: Into<T>
+            + Add<Output = F>
+            + Div<Output = F>
+            + Mul<Output = F>
+            + Sub<Output = F>
+            + Neg<Output = F>
+            + Copy
+            + Debug,
+        I: IntoIterator<Item = (F, F)>,
+    {
+        for (a, b) in iter {
+            assert_eq!((a + b).into(), a.into() + b.into());
+            assert_eq!((a - b).into(), a.into() - b.into());
+            assert_eq!((a * b).into(), a.into() * b.into());
+            assert_eq!((a / b).into(), a.into() / b.into());
+            assert_eq!((-a).into(), -a.into());
+            assert_eq!((-b).into(), -b.into());
+        }
+    }
+
+    #[test]
+    fn test_ops_f32() {
+        let mut rng = rand::thread_rng();
+        let iter = iter::repeat(()).map(|_| rng.gen());
+
+        test_ops::<F32, f32, _>(iter.take(1000));
+    }
+
+    #[test]
+    fn test_ops_f64() {
+        let mut rng = rand::thread_rng();
+        let iter = iter::repeat(()).map(|_| rng.gen());
+
+        test_ops::<F64, f64, _>(iter.take(1000));
+    }
+
+    #[test]
+    fn test_neg_nan_f32() {
+        assert_eq!((-F32(0xff80_3210)).0, 0x7f80_3210);
+    }
+
+    #[test]
+    fn test_neg_nan_f64() {
+        assert_eq!((-F64(0xff80_3210_0000_0000)).0, 0x7f80_3210_0000_0000);
+    }
+}

src/prepare/mod.rs

@@ -0,0 +1,169 @@
+use alloc::vec::Vec;
+
+use crate::{
+    isa,
+    validation::{validate_module, Error, Validator},
+};
+use parity_wasm::elements::Module;
+
+mod compile;
+
+#[cfg(test)]
+mod tests;
+
+#[derive(Clone)]
+pub struct CompiledModule {
+    pub code_map: Vec<isa::Instructions>,
+    pub module: Module,
+}
+
+pub struct WasmiValidation {
+    code_map: Vec<isa::Instructions>,
+}
+
+// This implementation of `Validation` is compiling wasm code at the
+// validation time.
+impl Validator for WasmiValidation {
+    type Output = Vec<isa::Instructions>;
+    type FuncValidator = compile::Compiler;
+    fn new(_module: &Module) -> Self {
+        WasmiValidation {
+            // TODO: with capacity?
+            code_map: Vec::new(),
+        }
+    }
+    fn on_function_validated(&mut self, _index: u32, output: isa::Instructions) {
+        self.code_map.push(output);
+    }
+    fn finish(self) -> Vec<isa::Instructions> {
+        self.code_map
+    }
+}
+
+/// Validate a module and compile it to the internal representation.
+pub fn compile_module(module: Module) -> Result<CompiledModule, Error> {
+    let code_map = validate_module::<WasmiValidation>(&module)?;
+    Ok(CompiledModule { module, code_map })
+}
+
+/// Verify that the module doesn't use floating point instructions or types.
+///
+/// Returns `Err` if
+///
+/// - Any of function bodies uses a floating pointer instruction (an instruction that
+///   consumes or produces a value of a floating point type)
+/// - If a floating point type used in a definition of a function.
+pub fn deny_floating_point(module: &Module) -> Result<(), Error> {
+    use parity_wasm::elements::{
+        Instruction::{self, *},
+        Type, ValueType,
+    };
+
+    if let Some(code) = module.code_section() {
+        for op in code.bodies().iter().flat_map(|body| body.code().elements()) {
+            macro_rules! match_eq {
+                ($pattern:pat) => {
+                    |val| if let $pattern = *val { true } else { false }
+                };
+            }
+
+            const DENIED: &[fn(&Instruction) -> bool] = &[
+                match_eq!(F32Load(_, _)),
+                match_eq!(F64Load(_, _)),
+                match_eq!(F32Store(_, _)),
+                match_eq!(F64Store(_, _)),
+                match_eq!(F32Const(_)),
+                match_eq!(F64Const(_)),
+                match_eq!(F32Eq),
+                match_eq!(F32Ne),
+                match_eq!(F32Lt),
+                match_eq!(F32Gt),
+                match_eq!(F32Le),
+                match_eq!(F32Ge),
+                match_eq!(F64Eq),
+                match_eq!(F64Ne),
+                match_eq!(F64Lt),
+                match_eq!(F64Gt),
+                match_eq!(F64Le),
+                match_eq!(F64Ge),
+                match_eq!(F32Abs),
+                match_eq!(F32Neg),
+                match_eq!(F32Ceil),
+                match_eq!(F32Floor),
+                match_eq!(F32Trunc),
+                match_eq!(F32Nearest),
+                match_eq!(F32Sqrt),
+                match_eq!(F32Add),
+                match_eq!(F32Sub),
+                match_eq!(F32Mul),
+                match_eq!(F32Div),
+                match_eq!(F32Min),
+                match_eq!(F32Max),
+                match_eq!(F32Copysign),
+                match_eq!(F64Abs),
+                match_eq!(F64Neg),
+                match_eq!(F64Ceil),
+                match_eq!(F64Floor),
+                match_eq!(F64Trunc),
+                match_eq!(F64Nearest),
+                match_eq!(F64Sqrt),
+                match_eq!(F64Add),
+                match_eq!(F64Sub),
+                match_eq!(F64Mul),
+                match_eq!(F64Div),
+                match_eq!(F64Min),
+                match_eq!(F64Max),
+                match_eq!(F64Copysign),
+                match_eq!(F32ConvertSI32),
+                match_eq!(F32ConvertUI32),
+                match_eq!(F32ConvertSI64),
+                match_eq!(F32ConvertUI64),
+                match_eq!(F32DemoteF64),
+                match_eq!(F64ConvertSI32),
+                match_eq!(F64ConvertUI32),
+                match_eq!(F64ConvertSI64),
+                match_eq!(F64ConvertUI64),
+                match_eq!(F64PromoteF32),
+                match_eq!(F32ReinterpretI32),
+                match_eq!(F64ReinterpretI64),
+                match_eq!(I32TruncSF32),
+                match_eq!(I32TruncUF32),
+                match_eq!(I32TruncSF64),
+                match_eq!(I32TruncUF64),
+                match_eq!(I64TruncSF32),
+                match_eq!(I64TruncUF32),
+                match_eq!(I64TruncSF64),
+                match_eq!(I64TruncUF64),
+                match_eq!(I32ReinterpretF32),
+                match_eq!(I64ReinterpretF64),
+            ];
+
+            if DENIED.iter().any(|is_denied| is_denied(op)) {
+                return Err(Error(format!("Floating point operation denied: {:?}", op)));
+            }
+        }
+    }
+
+    if let (Some(sec), Some(types)) = (module.function_section(), module.type_section()) {
+        let types = types.types();
+
+        for sig in sec.entries() {
+            if let Some(typ) = types.get(sig.type_ref() as usize) {
+                match *typ {
+                    Type::Function(ref func) => {
+                        if func
+                            .params()
+                            .iter()
+                            .chain(func.return_type().as_ref())
+                            .any(|&typ| typ == ValueType::F32 || typ == ValueType::F64)
+                        {
+                            return Err(Error(format!("Use of floating point types denied")));
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    Ok(())
+}

src/prepare/tests.rs

@@ -0,0 +1,746 @@
+use super::{compile_module, CompiledModule};
+use parity_wasm::{deserialize_buffer, elements::Module};
+
+use isa;
+use wabt;
+
+fn validate(wat: &str) -> CompiledModule {
+    let wasm = wabt::wat2wasm(wat).unwrap();
+    let module = deserialize_buffer::<Module>(&wasm).unwrap();
+    let compiled_module = compile_module(module).unwrap();
+    compiled_module
+}
+
+fn compile(module: &CompiledModule) -> (Vec<isa::Instruction>, Vec<u32>) {
+    let code = &module.code_map[0];
+    let mut instructions = Vec::new();
+    let mut pcs = Vec::new();
+    let mut iter = code.iterate_from(0);
+    loop {
+        let pc = iter.position();
+        if let Some(instruction) = iter.next() {
+            instructions.push(instruction.clone());
+            pcs.push(pc);
+        } else {
+            break;
+        }
+    }
+
+    (instructions, pcs)
+}
+
+macro_rules! targets {
+	($($target:expr),*) => {
+		::isa::BrTargets::from_internal(
+			&[$($target,)*]
+				.iter()
+				.map(|&target| ::isa::InstructionInternal::BrTableTarget(target))
+				.collect::<Vec<_>>()[..]
+		)
+	};
+}
+
+#[test]
+fn implicit_return_no_value() {
+    let module = validate(
+        r#"
+		(module
+			(func (export "call")
+			)
+		)
+	"#,
+    );
+    let (code, _) = compile(&module);
+    assert_eq!(
+        code,
+        vec![isa::Instruction::Return(isa::DropKeep {
+            drop: 0,
+            keep: isa::Keep::None,
+        })]
+    )
+}
+
+#[test]
+fn implicit_return_with_value() {
+    let module = validate(
+        r#"
+		(module
+			(func (export "call") (result i32)
+				i32.const 0
+			)
+		)
+	"#,
+    );
+    let (code, _) = compile(&module);
+    assert_eq!(
+        code,
+        vec![
+            isa::Instruction::I32Const(0),
+            isa::Instruction::Return(isa::DropKeep {
+                drop: 0,
+                keep: isa::Keep::Single,
+            }),
+        ]
+    )
+}
+
+#[test]
+fn implicit_return_param() {
+    let module = validate(
+        r#"
+		(module
+			(func (export "call") (param i32)
+			)
+		)
+	"#,
+    );
+    let (code, _) = compile(&module);
+    assert_eq!(
+        code,
+        vec![isa::Instruction::Return(isa::DropKeep {
+            drop: 1,
+            keep: isa::Keep::None,
+        }),]
+    )
+}
+
+#[test]
+fn get_local() {
+    let module = validate(
+        r#"
+		(module
+			(func (export "call") (param i32) (result i32)
+				get_local 0
+			)
+		)
+	"#,
+    );
+    let (code, _) = compile(&module);
+    assert_eq!(
+        code,
+        vec![
+            isa::Instruction::GetLocal(1),
+            isa::Instruction::Return(isa::DropKeep {
+                drop: 1,
+                keep: isa::Keep::Single,
+            }),
+        ]
+    )
+}
+
+#[test]
+fn explicit_return() {
+    let module = validate(
+        r#"
+		(module
+			(func (export "call") (param i32) (result i32)
+				get_local 0
+				return
+			)
+		)
+	"#,
+    );
+    let (code, _) = compile(&module);
+    assert_eq!(
+        code,
+        vec![
+            isa::Instruction::GetLocal(1),
+            isa::Instruction::Return(isa::DropKeep {
+                drop: 1,
+                keep: isa::Keep::Single,
+            }),
+            isa::Instruction::Return(isa::DropKeep {
+                drop: 1,
+                keep: isa::Keep::Single,
+            }),
+        ]
+    )
+}
+
+#[test]
+fn add_params() {
+    let module = validate(
+        r#"
+		(module
+			(func (export "call") (param i32) (param i32) (result i32)
+				get_local 0
+				get_local 1
+				i32.add
+			)
+		)
+	"#,
+    );
+    let (code, _) = compile(&module);
+    assert_eq!(
+        code,
+        vec![
+            // This is tricky. Locals are now loaded from the stack. The load
+            // happens from address relative of the current stack pointer. The first load
+            // takes the value below the previous one (i.e the second argument) and then, it increments
+            // the stack pointer. And then the same thing hapens with the value below the previous one
+            // (which happens to be the value loaded by the first get_local).
+            isa::Instruction::GetLocal(2),
+            isa::Instruction::GetLocal(2),
+            isa::Instruction::I32Add,
+            isa::Instruction::Return(isa::DropKeep {
+                drop: 2,
+                keep: isa::Keep::Single,
+            }),
+        ]
+    )
+}
+
+#[test]
+fn drop_locals() {
+    let module = validate(
+        r#"
+		(module
+			(func (export "call") (param i32)
+				(local i32)
+				get_local 0
+				set_local 1
+			)
+		)
+	"#,
+    );
+    let (code, _) = compile(&module);
+    assert_eq!(
+        code,
+        vec![
+            isa::Instruction::GetLocal(2),
+            isa::Instruction::SetLocal(1),
+            isa::Instruction::Return(isa::DropKeep {
+                drop: 2,
+                keep: isa::Keep::None,
+            }),
+        ]
+    )
+}
+
+#[test]
+fn if_without_else() {
+    let module = validate(
+        r#"
+		(module
+			(func (export "call") (param i32) (result i32)
+				i32.const 1
+				if
+					i32.const 2
+					return
+				end
+				i32.const 3
+			)
+		)
+	"#,
+    );
+    let (code, pcs) = compile(&module);
+    assert_eq!(
+        code,
+        vec![
+            isa::Instruction::I32Const(1),
+            isa::Instruction::BrIfEqz(isa::Target {
+                dst_pc: pcs[4],
+                drop_keep: isa::DropKeep {
+                    drop: 0,
+                    keep: isa::Keep::None,
+                },
+            }),
+            isa::Instruction::I32Const(2),
+            isa::Instruction::Return(isa::DropKeep {
+                drop: 1,                 // 1 param
+                keep: isa::Keep::Single, // 1 result
+            }),
+            isa::Instruction::I32Const(3),
+            isa::Instruction::Return(isa::DropKeep {
+                drop: 1,
+                keep: isa::Keep::Single,
+            }),
+        ]
+    )
+}
+
+#[test]
+fn if_else() {
+    let module = validate(
+        r#"
+		(module
+			(func (export "call")
+				(local i32)
+				i32.const 1
+				if
+					i32.const 2
+					set_local 0
+				else
+					i32.const 3
+					set_local 0
+				end
+			)
+		)
+	"#,
+    );
+    let (code, pcs) = compile(&module);
+    assert_eq!(
+        code,
+        vec![
+            isa::Instruction::I32Const(1),
+            isa::Instruction::BrIfEqz(isa::Target {
+                dst_pc: pcs[5],
+                drop_keep: isa::DropKeep {
+                    drop: 0,
+                    keep: isa::Keep::None,
+                },
+            }),
+            isa::Instruction::I32Const(2),
+            isa::Instruction::SetLocal(1),
+            isa::Instruction::Br(isa::Target {
+                dst_pc: pcs[7],
+                drop_keep: isa::DropKeep {
+                    drop: 0,
+                    keep: isa::Keep::None,
+                },
+            }),
+            isa::Instruction::I32Const(3),
+            isa::Instruction::SetLocal(1),
+            isa::Instruction::Return(isa::DropKeep {
+                drop: 1,
+                keep: isa::Keep::None,
+            }),
+        ]
+    )
+}
+
+#[test]
+fn if_else_returns_result() {
+    let module = validate(
+        r#"
+		(module
+			(func (export "call")
+				i32.const 1
+				if (result i32)
+					i32.const 2
+				else
+					i32.const 3
+				end
+				drop
+			)
+		)
+	"#,
+    );
+    let (code, pcs) = compile(&module);
+    assert_eq!(
+        code,
+        vec![
+            isa::Instruction::I32Const(1),
+            isa::Instruction::BrIfEqz(isa::Target {
+                dst_pc: pcs[4],
+                drop_keep: isa::DropKeep {
+                    drop: 0,
+                    keep: isa::Keep::None,
+                },
+            }),
+            isa::Instruction::I32Const(2),
+            isa::Instruction::Br(isa::Target {
+                dst_pc: pcs[5],
+                drop_keep: isa::DropKeep {
+                    drop: 0,
+                    keep: isa::Keep::None,
+                },
+            }),
+            isa::Instruction::I32Const(3),
+            isa::Instruction::Drop,
+            isa::Instruction::Return(isa::DropKeep {
+                drop: 0,
+                keep: isa::Keep::None,
+            }),
+        ]
+    )
+}
+
+#[test]
+fn if_else_branch_from_true_branch() {
+    let module = validate(
+        r#"
+		(module
+			(func (export "call")
+				i32.const 1
+				if (result i32)
+					i32.const 1
+					i32.const 1
+					br_if 0
+					drop
+					i32.const 2
+				else
+					i32.const 3
+				end
+				drop
+			)
+		)
+	"#,
+    );
+    let (code, pcs) = compile(&module);
+    assert_eq!(
+        code,
+        vec![
+            isa::Instruction::I32Const(1),
+            isa::Instruction::BrIfEqz(isa::Target {
+                dst_pc: pcs[8],
+                drop_keep: isa::DropKeep {
+                    drop: 0,
+                    keep: isa::Keep::None,
+                },
+            }),
+            isa::Instruction::I32Const(1),
+            isa::Instruction::I32Const(1),
+            isa::Instruction::BrIfNez(isa::Target {
+                dst_pc: pcs[9],
+                drop_keep: isa::DropKeep {
+                    drop: 0,
+                    keep: isa::Keep::Single,
+                },
+            }),
+            isa::Instruction::Drop,
+            isa::Instruction::I32Const(2),
+            isa::Instruction::Br(isa::Target {
+                dst_pc: pcs[9],
+                drop_keep: isa::DropKeep {
+                    drop: 0,
+                    keep: isa::Keep::None,
+                },
+            }),
+            isa::Instruction::I32Const(3),
+            isa::Instruction::Drop,
+            isa::Instruction::Return(isa::DropKeep {
+                drop: 0,
+                keep: isa::Keep::None,
+            }),
+        ]
+    )
+}
+
+#[test]
+fn if_else_branch_from_false_branch() {
+    let module = validate(
+        r#"
+		(module
+			(func (export "call")
+				i32.const 1
+				if (result i32)
+					i32.const 1
+				else
+					i32.const 2
+					i32.const 1
+					br_if 0
+					drop
+					i32.const 3
+				end
+				drop
+			)
+		)
+	"#,
+    );
+    let (code, pcs) = compile(&module);
+    assert_eq!(
+        code,
+        vec![
+            isa::Instruction::I32Const(1),
+            isa::Instruction::BrIfEqz(isa::Target {
+                dst_pc: pcs[4],
+                drop_keep: isa::DropKeep {
+                    drop: 0,
+                    keep: isa::Keep::None,
+                },
+            }),
+            isa::Instruction::I32Const(1),
+            isa::Instruction::Br(isa::Target {
+                dst_pc: pcs[9],
+                drop_keep: isa::DropKeep {
+                    drop: 0,
+                    keep: isa::Keep::None,
+                },
+            }),
+            isa::Instruction::I32Const(2),
+            isa::Instruction::I32Const(1),
+            isa::Instruction::BrIfNez(isa::Target {
+                dst_pc: pcs[9],
+                drop_keep: isa::DropKeep {
+                    drop: 0,
+                    keep: isa::Keep::Single,
+                },
+            }),
+            isa::Instruction::Drop,
+            isa::Instruction::I32Const(3),
+            isa::Instruction::Drop,
+            isa::Instruction::Return(isa::DropKeep {
+                drop: 0,
+                keep: isa::Keep::None,
+            }),
+        ]
+    )
+}
+
+#[test]
+fn loop_() {
+    let module = validate(
+        r#"
+		(module
+			(func (export "call")
+				loop (result i32)
+					i32.const 1
+					br_if 0
+					i32.const 2
+				end
+				drop
+			)
+		)
+	"#,
+    );
+    let (code, _) = compile(&module);
+    assert_eq!(
+        code,
+        vec![
+            isa::Instruction::I32Const(1),
+            isa::Instruction::BrIfNez(isa::Target {
+                dst_pc: 0,
+                drop_keep: isa::DropKeep {
+                    drop: 0,
+                    keep: isa::Keep::None,
+                },
+            }),
+            isa::Instruction::I32Const(2),
+            isa::Instruction::Drop,
+            isa::Instruction::Return(isa::DropKeep {
+                drop: 0,
+                keep: isa::Keep::None,
+            }),
+        ]
+    )
+}
+
+#[test]
+fn loop_empty() {
+    let module = validate(
+        r#"
+		(module
+			(func (export "call")
+				loop
+				end
+			)
+		)
+	"#,
+    );
+    let (code, _) = compile(&module);
+    assert_eq!(
+        code,
+        vec![isa::Instruction::Return(isa::DropKeep {
+            drop: 0,
+            keep: isa::Keep::None,
+        }),]
+    )
+}
+
+#[test]
+fn spec_as_br_if_value_cond() {
+    use self::isa::Instruction::*;
+
+    let module = validate(
+        r#"
+		  (func (export "as-br_if-value-cond") (result i32)
+            (block (result i32)
+              (drop
+                (br_if 0
+                  (i32.const 6)
+                  (br_table 0 0
+                    (i32.const 9)
+                    (i32.const 0)
+                  )
+                )
+              )
+            (i32.const 7)
+          )
+        )
+	"#,
+    );
+    let (code, _) = compile(&module);
+    assert_eq!(
+        code,
+        vec![
+            I32Const(6),
+            I32Const(9),
+            I32Const(0),
+            isa::Instruction::BrTable(targets![
+                isa::Target {
+                    dst_pc: 9,
+                    drop_keep: isa::DropKeep {
+                        drop: 1,
+                        keep: isa::Keep::Single
+                    }
+                },
+                isa::Target {
+                    dst_pc: 9,
+                    drop_keep: isa::DropKeep {
+                        drop: 1,
+                        keep: isa::Keep::Single
+                    }
+                }
+            ]),
+            BrIfNez(isa::Target {
+                dst_pc: 9,
+                drop_keep: isa::DropKeep {
+                    drop: 0,
+                    keep: isa::Keep::Single
+                }
+            }),
+            Drop,
+            I32Const(7),
+            Return(isa::DropKeep {
+                drop: 0,
+                keep: isa::Keep::Single
+            })
+        ]
+    );
+}
+
+#[test]
+fn brtable() {
+    let module = validate(
+        r#"
+		(module
+			(func (export "call")
+				block $1
+					loop $2
+						i32.const 0
+						br_table $2 $1
+					end
+				end
+			)
+		)
+	"#,
+    );
+    let (code, pcs) = compile(&module);
+    assert_eq!(
+        code,
+        vec![
+            isa::Instruction::I32Const(0),
+            isa::Instruction::BrTable(targets![
+                isa::Target {
+                    dst_pc: 0,
+                    drop_keep: isa::DropKeep {
+                        drop: 0,
+                        keep: isa::Keep::None,
+                    },
+                },
+                isa::Target {
+                    dst_pc: pcs[2],
+                    drop_keep: isa::DropKeep {
+                        drop: 0,
+                        keep: isa::Keep::None,
+                    },
+                }
+            ]),
+            isa::Instruction::Return(isa::DropKeep {
+                drop: 0,
+                keep: isa::Keep::None,
+            }),
+        ]
+    )
+}
+
+#[test]
+fn brtable_returns_result() {
+    let module = validate(
+        r#"
+		(module
+			(func (export "call")
+				block $1 (result i32)
+					block $2 (result i32)
+						i32.const 0
+						i32.const 1
+						br_table $2 $1
+					end
+					unreachable
+				end
+				drop
+			)
+		)
+	"#,
+    );
+    let (code, pcs) = compile(&module);
+    println!("{:?}", (&code, &pcs));
+    assert_eq!(
+        code,
+        vec![
+            isa::Instruction::I32Const(0),
+            isa::Instruction::I32Const(1),
+            isa::Instruction::BrTable(targets![
+                isa::Target {
+                    dst_pc: pcs[3],
+                    drop_keep: isa::DropKeep {
+                        drop: 0,
+                        keep: isa::Keep::Single,
+                    },
+                },
+                isa::Target {
+                    dst_pc: pcs[4],
+                    drop_keep: isa::DropKeep {
+                        keep: isa::Keep::Single,
+                        drop: 0,
+                    },
+                }
+            ]),
+            isa::Instruction::Unreachable,
+            isa::Instruction::Drop,
+            isa::Instruction::Return(isa::DropKeep {
+                drop: 0,
+                keep: isa::Keep::None,
+            }),
+        ]
+    )
+}
+
+#[test]
+fn wabt_example() {
+    let module = validate(
+        r#"
+		(module
+			(func (export "call") (param i32) (result i32)
+				block $exit
+					get_local 0
+					br_if $exit
+					i32.const 1
+					return
+				end
+				i32.const 2
+				return
+			)
+		)
+	"#,
+    );
+    let (code, pcs) = compile(&module);
+    assert_eq!(
+        code,
+        vec![
+            isa::Instruction::GetLocal(1),
+            isa::Instruction::BrIfNez(isa::Target {
+                dst_pc: pcs[4],
+                drop_keep: isa::DropKeep {
+                    drop: 0,
+                    keep: isa::Keep::None,
+                },
+            }),
+            isa::Instruction::I32Const(1),
+            isa::Instruction::Return(isa::DropKeep {
+                drop: 1, // 1 parameter
+                keep: isa::Keep::Single,
+            }),
+            isa::Instruction::I32Const(2),
+            isa::Instruction::Return(isa::DropKeep {
+                drop: 1,
+                keep: isa::Keep::Single,
+            }),
+            isa::Instruction::Return(isa::DropKeep {
+                drop: 1,
+                keep: isa::Keep::Single,
+            }),
+        ]
+    )
+}

src/table.rs

@@ -1,11 +1,11 @@
-use std::u32;
-use std::fmt;
-use std::cell::RefCell;
-use std::rc::Rc;
-use parity_wasm::elements::ResizableLimits;
-use Error;
+use alloc::{rc::Rc, vec::Vec};
+use core::cell::RefCell;
+use core::fmt;
+use core::u32;
 use func::FuncRef;
 use module::check_limits;
+use parity_wasm::elements::ResizableLimits;
+use Error;
 
 /// Reference to a table (See [`TableInstance`] for details).
 ///
@@ -16,11 +16,11 @@ use module::check_limits;
 #[derive(Clone, Debug)]
 pub struct TableRef(Rc<TableInstance>);
 
-impl ::std::ops::Deref for TableRef {
-	type Target = TableInstance;
-	fn deref(&self) -> &TableInstance {
-		&self.0
-	}
+impl ::core::ops::Deref for TableRef {
+    type Target = TableInstance;
+    fn deref(&self) -> &TableInstance {
+        &self.0
+    }
 }
 
 /// Runtime representation of a table.
@@ -37,118 +37,118 @@ impl ::std::ops::Deref for TableRef {
 /// [`grow`]: #method.grow
 ///
 pub struct TableInstance {
-	/// Table limits.
-	limits: ResizableLimits,
-	/// Table memory buffer.
-	buffer: RefCell<Vec<Option<FuncRef>>>,
+    /// Table limits.
+    limits: ResizableLimits,
+    /// Table memory buffer.
+    buffer: RefCell<Vec<Option<FuncRef>>>,
 }
 
 impl fmt::Debug for TableInstance {
-	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-		f.debug_struct("TableInstance")
-			.field("limits", &self.limits)
-			.field("buffer.len", &self.buffer.borrow().len())
-			.finish()
-	}
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("TableInstance")
+            .field("limits", &self.limits)
+            .field("buffer.len", &self.buffer.borrow().len())
+            .finish()
+    }
 }
 
 impl TableInstance {
-	/// Allocate a table instance.
-	///
-	/// The table allocated with initial size, specified by `initial_size`.
-	/// Maximum size can be specified by `maximum_size`.
-	///
-	/// All table elements are allocated uninitialized.
-	///
-	/// # Errors
-	///
-	/// Returns `Err` if `initial_size` is greater than `maximum_size`.
-	pub fn alloc(initial_size: u32, maximum_size: Option<u32>) -> Result<TableRef, Error> {
-		let table = TableInstance::new(ResizableLimits::new(initial_size, maximum_size))?;
-		Ok(TableRef(Rc::new(table)))
-	}
+    /// Allocate a table instance.
+    ///
+    /// The table allocated with initial size, specified by `initial_size`.
+    /// Maximum size can be specified by `maximum_size`.
+    ///
+    /// All table elements are allocated uninitialized.
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if `initial_size` is greater than `maximum_size`.
+    pub fn alloc(initial_size: u32, maximum_size: Option<u32>) -> Result<TableRef, Error> {
+        let table = TableInstance::new(ResizableLimits::new(initial_size, maximum_size))?;
+        Ok(TableRef(Rc::new(table)))
+    }
 
-	fn new(limits: ResizableLimits) -> Result<TableInstance, Error> {
-		check_limits(&limits)?;
-		Ok(TableInstance {
-			buffer: RefCell::new(vec![None; limits.initial() as usize]),
-			limits: limits,
-		})
-	}
+    fn new(limits: ResizableLimits) -> Result<TableInstance, Error> {
+        check_limits(&limits)?;
+        Ok(TableInstance {
+            buffer: RefCell::new(vec![None; limits.initial() as usize]),
+            limits: limits,
+        })
+    }
 
-	/// Return table limits.
-	pub(crate) fn limits(&self) -> &ResizableLimits {
-		&self.limits
-	}
+    /// Return table limits.
+    pub(crate) fn limits(&self) -> &ResizableLimits {
+        &self.limits
+    }
 
-	/// Returns size this table was created with.
-	pub fn initial_size(&self) -> u32 {
-		self.limits.initial()
-	}
+    /// Returns size this table was created with.
+    pub fn initial_size(&self) -> u32 {
+        self.limits.initial()
+    }
 
-	/// Returns maximum size `TableInstance` can grow to.
-	pub fn maximum_size(&self) -> Option<u32> {
-		self.limits.maximum()
-	}
+    /// Returns maximum size `TableInstance` can grow to.
+    pub fn maximum_size(&self) -> Option<u32> {
+        self.limits.maximum()
+    }
 
-	/// Returns current size of the table.
-	pub fn current_size(&self) -> u32 {
-		self.buffer.borrow().len() as u32
-	}
+    /// Returns current size of the table.
+    pub fn current_size(&self) -> u32 {
+        self.buffer.borrow().len() as u32
+    }
 
-	/// Increases the size of the table by given number of elements.
-	///
-	/// # Errors
-	///
-	/// Returns `Err` if tried to allocate more elements than permited by limit.
-	pub fn grow(&self, by: u32) -> Result<(), Error> {
-		let mut buffer = self.buffer.borrow_mut();
-		let maximum_size = self.maximum_size().unwrap_or(u32::MAX);
-		let new_size = self.current_size().checked_add(by)
-			.and_then(|new_size| {
-				if maximum_size < new_size {
-					None
-				} else {
-					Some(new_size)
-				}
-			})
-			.ok_or_else(||
-				Error::Table(format!(
-					"Trying to grow table by {} items when there are already {} items",
-					by,
-					self.current_size(),
-				))
-			)?;
-		buffer.resize(new_size as usize, None);
-		Ok(())
-	}
+    /// Increases the size of the table by given number of elements.
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if tried to allocate more elements than permited by limit.
+    pub fn grow(&self, by: u32) -> Result<(), Error> {
+        let mut buffer = self.buffer.borrow_mut();
+        let maximum_size = self.maximum_size().unwrap_or(u32::MAX);
+        let new_size = self
+            .current_size()
+            .checked_add(by)
+            .and_then(|new_size| {
+                if maximum_size < new_size {
+                    None
+                } else {
+                    Some(new_size)
+                }
+            })
+            .ok_or_else(|| {
+                Error::Table(format!(
+                    "Trying to grow table by {} items when there are already {} items",
+                    by,
+                    self.current_size(),
+                ))
+            })?;
+        buffer.resize(new_size as usize, None);
+        Ok(())
+    }
 
-	/// Get the specific value in the table
-	pub fn get(&self, offset: u32) -> Result<Option<FuncRef>, Error> {
-		let buffer = self.buffer.borrow();
-		let buffer_len = buffer.len();
-		let table_elem = buffer.get(offset as usize).cloned().ok_or_else(||
-			Error::Table(format!(
-				"trying to read table item with index {} when there are only {} items",
-				offset,
-				buffer_len
-			)),
-		)?;
-		Ok(table_elem)
-	}
+    /// Get the specific value in the table
+    pub fn get(&self, offset: u32) -> Result<Option<FuncRef>, Error> {
+        let buffer = self.buffer.borrow();
+        let buffer_len = buffer.len();
+        let table_elem = buffer.get(offset as usize).cloned().ok_or_else(|| {
+            Error::Table(format!(
+                "trying to read table item with index {} when there are only {} items",
+                offset, buffer_len
+            ))
+        })?;
+        Ok(table_elem)
+    }
 
-	/// Set the table element to the specified function.
-	pub fn set(&self, offset: u32, value: Option<FuncRef>) -> Result<(), Error> {
-		let mut buffer = self.buffer.borrow_mut();
-		let buffer_len = buffer.len();
-		let table_elem = buffer.get_mut(offset as usize).ok_or_else(||
-			Error::Table(format!(
-				"trying to update table item with index {} when there are only {} items",
-				offset,
-				buffer_len
-			))
-		)?;
-		*table_elem = value;
-		Ok(())
-	}
+    /// Set the table element to the specified function.
+    pub fn set(&self, offset: u32, value: Option<FuncRef>) -> Result<(), Error> {
+        let mut buffer = self.buffer.borrow_mut();
+        let buffer_len = buffer.len();
+        let table_elem = buffer.get_mut(offset as usize).ok_or_else(|| {
+            Error::Table(format!(
+                "trying to update table item with index {} when there are only {} items",
+                offset, buffer_len
+            ))
+        })?;
+        *table_elem = value;
+        Ok(())
+    }
 }

src/tests/mod.rs

@@ -1,5 +1,5 @@
 use wabt;
-use {Module};
+use Module;
 
 mod host;
 mod wasm;
@@ -12,25 +12,31 @@ fn assert_std_err_impl<T: ::std::error::Error>() {}
 
 #[test]
 fn assert_error_properties() {
-	assert_send::<Error>();
-	assert_sync::<Error>();
-	assert_std_err_impl::<Error>();
+    assert_send::<Error>();
+    assert_sync::<Error>();
+    assert_std_err_impl::<Error>();
 }
 
 /// Test that converting an u32 (u64) that does not fit in an i32 (i64)
 /// to a RuntimeValue and back works as expected and the number remains unchanged.
 #[test]
 fn unsigned_to_runtime_value() {
-	use super::RuntimeValue;
+    use super::RuntimeValue;
 
-	let overflow_i32: u32 = ::std::i32::MAX as u32 + 1;
-	assert_eq!(RuntimeValue::from(overflow_i32).try_into::<u32>().unwrap(), overflow_i32);
+    let overflow_i32: u32 = ::core::i32::MAX as u32 + 1;
+    assert_eq!(
+        RuntimeValue::from(overflow_i32).try_into::<u32>().unwrap(),
+        overflow_i32
+    );
 
-	let overflow_i64: u64 = ::std::i64::MAX as u64 + 1;
-	assert_eq!(RuntimeValue::from(overflow_i64).try_into::<u64>().unwrap(), overflow_i64);
+    let overflow_i64: u64 = ::core::i64::MAX as u64 + 1;
+    assert_eq!(
+        RuntimeValue::from(overflow_i64).try_into::<u64>().unwrap(),
+        overflow_i64
+    );
 }
 
 pub fn parse_wat(source: &str) -> Module {
-	let wasm_binary = wabt::wat2wasm(source).expect("Failed to parse wat source");
-	Module::from_buffer(wasm_binary).expect("Failed to load parsed module")
+    let wasm_binary = wabt::wat2wasm(source).expect("Failed to parse wat source");
+    Module::from_buffer(wasm_binary).expect("Failed to load parsed module")
 }

src/tests/wasm.rs

@@ -1,110 +1,113 @@
-use {
-	Error, Signature, FuncRef, GlobalInstance, GlobalRef, ImportsBuilder, MemoryInstance,
-    MemoryRef, ModuleImportResolver, ModuleInstance, NopExternals, RuntimeValue,
-    TableInstance, TableRef, Module, GlobalDescriptor, TableDescriptor, MemoryDescriptor,
-};
 use memory_units::Pages;
 use std::fs::File;
+use {
+    Error, FuncRef, GlobalDescriptor, GlobalInstance, GlobalRef, ImportsBuilder, MemoryDescriptor,
+    MemoryInstance, MemoryRef, Module, ModuleImportResolver, ModuleInstance, NopExternals,
+    RuntimeValue, Signature, TableDescriptor, TableInstance, TableRef,
+};
 
 struct Env {
-	table_base: GlobalRef,
-	memory_base: GlobalRef,
-	memory: MemoryRef,
-	table: TableRef,
+    table_base: GlobalRef,
+    memory_base: GlobalRef,
+    memory: MemoryRef,
+    table: TableRef,
 }
 
 impl Env {
-	fn new() -> Env {
-		Env {
-			table_base: GlobalInstance::alloc(RuntimeValue::I32(0), false),
-			memory_base: GlobalInstance::alloc(RuntimeValue::I32(0), false),
-			memory: MemoryInstance::alloc(Pages(256), None).unwrap(),
-			table: TableInstance::alloc(64, None).unwrap(),
-		}
-	}
+    fn new() -> Env {
+        Env {
+            table_base: GlobalInstance::alloc(RuntimeValue::I32(0), false),
+            memory_base: GlobalInstance::alloc(RuntimeValue::I32(0), false),
+            memory: MemoryInstance::alloc(Pages(256), None).unwrap(),
+            table: TableInstance::alloc(64, None).unwrap(),
+        }
+    }
 }
 
 impl ModuleImportResolver for Env {
-	fn resolve_func(&self, _field_name: &str, _func_type: &Signature) -> Result<FuncRef, Error> {
-		Err(Error::Instantiation(
-			"env module doesn't provide any functions".into(),
-		))
-	}
+    fn resolve_func(&self, _field_name: &str, _func_type: &Signature) -> Result<FuncRef, Error> {
+        Err(Error::Instantiation(
+            "env module doesn't provide any functions".into(),
+        ))
+    }
 
-	fn resolve_global(
-		&self,
-		field_name: &str,
-		_global_type: &GlobalDescriptor,
-	) -> Result<GlobalRef, Error> {
-		match field_name {
-			"tableBase" => Ok(self.table_base.clone()),
-			"memoryBase" => Ok(self.memory_base.clone()),
-			_ => Err(Error::Instantiation(format!(
-				"env module doesn't provide global '{}'",
-				field_name
-			))),
-		}
-	}
+    fn resolve_global(
+        &self,
+        field_name: &str,
+        _global_type: &GlobalDescriptor,
+    ) -> Result<GlobalRef, Error> {
+        match field_name {
+            "tableBase" => Ok(self.table_base.clone()),
+            "memoryBase" => Ok(self.memory_base.clone()),
+            _ => Err(Error::Instantiation(format!(
+                "env module doesn't provide global '{}'",
+                field_name
+            ))),
+        }
+    }
 
-	fn resolve_memory(
-		&self,
-		field_name: &str,
-		_memory_type: &MemoryDescriptor,
-	) -> Result<MemoryRef, Error> {
-		match field_name {
-			"memory" => Ok(self.memory.clone()),
-			_ => Err(Error::Instantiation(format!(
-				"env module doesn't provide memory '{}'",
-				field_name
-			))),
-		}
-	}
+    fn resolve_memory(
+        &self,
+        field_name: &str,
+        _memory_type: &MemoryDescriptor,
+    ) -> Result<MemoryRef, Error> {
+        match field_name {
+            "memory" => Ok(self.memory.clone()),
+            _ => Err(Error::Instantiation(format!(
+                "env module doesn't provide memory '{}'",
+                field_name
+            ))),
+        }
+    }
 
-	fn resolve_table(&self, field_name: &str, _table_type: &TableDescriptor) -> Result<TableRef, Error> {
-		match field_name {
-			"table" => Ok(self.table.clone()),
-			_ => Err(Error::Instantiation(
-				format!("env module doesn't provide table '{}'", field_name),
-			)),
-		}
-	}
+    fn resolve_table(
+        &self,
+        field_name: &str,
+        _table_type: &TableDescriptor,
+    ) -> Result<TableRef, Error> {
+        match field_name {
+            "table" => Ok(self.table.clone()),
+            _ => Err(Error::Instantiation(format!(
+                "env module doesn't provide table '{}'",
+                field_name
+            ))),
+        }
+    }
 }
 
 fn load_from_file(filename: &str) -> Module {
-	use std::io::prelude::*;
-	let mut file = File::open(filename).unwrap();
-	let mut buf = Vec::new();
-	file.read_to_end(&mut buf).unwrap();
-	let wasm_buf = ::wabt::wat2wasm(&buf).unwrap();
-	Module::from_buffer(wasm_buf).unwrap()
+    use std::io::prelude::*;
+    let mut file = File::open(filename).unwrap();
+    let mut buf = Vec::new();
+    file.read_to_end(&mut buf).unwrap();
+    let wasm_buf = ::wabt::wat2wasm(&buf).unwrap();
+    Module::from_buffer(wasm_buf).unwrap()
 }
 
 #[test]
 fn interpreter_inc_i32() {
-	// Name of function contained in WASM file (note the leading underline)
-	const FUNCTION_NAME: &'static str = "_inc_i32";
-	// The WASM file containing the module and function
-	const WASM_FILE: &str = &"res/fixtures/inc_i32.wast";
+    // Name of function contained in WASM file (note the leading underline)
+    const FUNCTION_NAME: &'static str = "_inc_i32";
+    // The WASM file containing the module and function
+    const WASM_FILE: &str = &"res/fixtures/inc_i32.wast";
 
-	let module = load_from_file(WASM_FILE);
+    let module = load_from_file(WASM_FILE);
 
-	let env = Env::new();
+    let env = Env::new();
 
-	let instance = ModuleInstance::new(
-		&module,
-		&ImportsBuilder::new().with_resolver("env", &env),
-	).expect("Failed to instantiate module")
-		.assert_no_start();
+    let instance = ModuleInstance::new(&module, &ImportsBuilder::new().with_resolver("env", &env))
+        .expect("Failed to instantiate module")
+        .assert_no_start();
 
-	let i32_val = 42;
-	// the functions expects a single i32 parameter
-	let args = &[RuntimeValue::I32(i32_val)];
-	let exp_retval = Some(RuntimeValue::I32(i32_val + 1));
+    let i32_val = 42;
+    // the functions expects a single i32 parameter
+    let args = &[RuntimeValue::I32(i32_val)];
+    let exp_retval = Some(RuntimeValue::I32(i32_val + 1));
 
-	let retval = instance
-		.invoke_export(FUNCTION_NAME, args, &mut NopExternals)
-		.expect("");
-	assert_eq!(exp_retval, retval);
+    let retval = instance
+        .invoke_export(FUNCTION_NAME, args, &mut NopExternals)
+        .expect("");
+    assert_eq!(exp_retval, retval);
 }
 
 #[test]
@@ -114,18 +117,15 @@ fn interpreter_accumulate_u8() {
     // The WASM file containing the module and function
     const WASM_FILE: &str = &"res/fixtures/accumulate_u8.wast";
     // The octet sequence being accumulated
-    const BUF: &[u8] = &[9,8,7,6,5,4,3,2,1];
-
+    const BUF: &[u8] = &[9, 8, 7, 6, 5, 4, 3, 2, 1];
 
     // Load the module-structure from wasm-file and add to program
-	let module = load_from_file(WASM_FILE);
+    let module = load_from_file(WASM_FILE);
 
-	let env = Env::new();
-	let instance = ModuleInstance::new(
-		&module,
-		&ImportsBuilder::new().with_resolver("env", &env),
-	).expect("Failed to instantiate module")
-		.assert_no_start();
+    let env = Env::new();
+    let instance = ModuleInstance::new(&module, &ImportsBuilder::new().with_resolver("env", &env))
+        .expect("Failed to instantiate module")
+        .assert_no_start();
 
     let env_memory = env.memory.clone();
 
@@ -134,7 +134,10 @@ fn interpreter_accumulate_u8() {
     let _ = env_memory.set(offset, BUF);
 
     // Set up the function argument list and invoke the function
-    let args = &[RuntimeValue::I32(BUF.len() as i32), RuntimeValue::I32(offset as i32)];
+    let args = &[
+        RuntimeValue::I32(BUF.len() as i32),
+        RuntimeValue::I32(offset as i32),
+    ];
     let retval = instance
         .invoke_export(FUNCTION_NAME, args, &mut NopExternals)
         .expect("Failed to execute function");

src/types.rs

@@ -1,7 +1,8 @@
-use std::borrow::Cow;
+use alloc::borrow::Cow;
 
 use parity_wasm::elements::{
-	FunctionType, ValueType as EValueType, GlobalType, TableType, MemoryType};
+    FunctionType, GlobalType, MemoryType, TableType, ValueType as EValueType,
+};
 
 /// Signature of a [function].
 ///
@@ -13,55 +14,60 @@ use parity_wasm::elements::{
 /// [function]: struct.FuncInstance.html
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Signature {
-	params: Cow<'static, [ValueType]>,
-	return_type: Option<ValueType>,
+    params: Cow<'static, [ValueType]>,
+    return_type: Option<ValueType>,
 }
 
 impl Signature {
-	/// Creates new signature with givens
-	/// parameter types and optional return type.
-	///
-	/// # Examples
-	///
-	/// ```rust
-	/// use wasmi::{Signature, ValueType};
-	///
-	/// // s1: (i32) -> ()
-	/// let s1 = Signature::new(&[ValueType::I32][..], None);
-	///
-	/// // s2: () -> i32
-	/// let s2 = Signature::new(&[][..], Some(ValueType::I32));
-	///
-	/// // s3: (I64) -> ()
-	/// let dynamic_params = vec![ValueType::I64];
-	/// let s3 = Signature::new(dynamic_params, None);
-	/// ```
-	pub fn new<C: Into<Cow<'static, [ValueType]>>>(
-		params: C,
-		return_type: Option<ValueType>
-	) -> Signature {
-		Signature {
-			params: params.into(),
-			return_type: return_type,
-		}
-	}
+    /// Creates new signature with givens
+    /// parameter types and optional return type.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use wasmi::{Signature, ValueType};
+    ///
+    /// // s1: (i32) -> ()
+    /// let s1 = Signature::new(&[ValueType::I32][..], None);
+    ///
+    /// // s2: () -> i32
+    /// let s2 = Signature::new(&[][..], Some(ValueType::I32));
+    ///
+    /// // s3: (I64) -> ()
+    /// let dynamic_params = vec![ValueType::I64];
+    /// let s3 = Signature::new(dynamic_params, None);
+    /// ```
+    pub fn new<C: Into<Cow<'static, [ValueType]>>>(
+        params: C,
+        return_type: Option<ValueType>,
+    ) -> Signature {
+        Signature {
+            params: params.into(),
+            return_type: return_type,
+        }
+    }
 
-	/// Returns parameter types of this signature.
-	pub fn params(&self) -> &[ValueType] {
-		&self.params.as_ref()
-	}
+    /// Returns parameter types of this signature.
+    pub fn params(&self) -> &[ValueType] {
+        &self.params.as_ref()
+    }
 
-	/// Returns return type of this signature.
-	pub fn return_type(&self) -> Option<ValueType> {
-		self.return_type
-	}
+    /// Returns return type of this signature.
+    pub fn return_type(&self) -> Option<ValueType> {
+        self.return_type
+    }
 
-	pub(crate) fn from_elements(func_type: &FunctionType) -> Signature {
-		Signature {
-			params: func_type.params().iter().cloned().map(ValueType::from_elements).collect(),
-			return_type: func_type.return_type().map(ValueType::from_elements),
-		}
-	}
+    pub(crate) fn from_elements(func_type: &FunctionType) -> Signature {
+        Signature {
+            params: func_type
+                .params()
+                .iter()
+                .cloned()
+                .map(ValueType::from_elements)
+                .collect(),
+            return_type: func_type.return_type().map(ValueType::from_elements),
+        }
+    }
 }
 
 /// Type of a value.
@@ -71,34 +77,34 @@ impl Signature {
 /// [`RuntimeValue`]: enum.RuntimeValue.html
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub enum ValueType {
-	/// 32-bit signed or unsigned integer.
-	I32,
-	/// 64-bit signed or unsigned integer.
-	I64,
-	/// 32-bit IEEE 754-2008 floating point number.
-	F32,
-	/// 64-bit IEEE 754-2008 floating point number.
-	F64,
+    /// 32-bit signed or unsigned integer.
+    I32,
+    /// 64-bit signed or unsigned integer.
+    I64,
+    /// 32-bit IEEE 754-2008 floating point number.
+    F32,
+    /// 64-bit IEEE 754-2008 floating point number.
+    F64,
 }
 
 impl ValueType {
-	pub(crate) fn from_elements(value_type: EValueType) -> ValueType {
-		match value_type {
-			EValueType::I32 => ValueType::I32,
-			EValueType::I64 => ValueType::I64,
-			EValueType::F32 => ValueType::F32,
-			EValueType::F64 => ValueType::F64,
-		}
-	}
+    pub(crate) fn from_elements(value_type: EValueType) -> ValueType {
+        match value_type {
+            EValueType::I32 => ValueType::I32,
+            EValueType::I64 => ValueType::I64,
+            EValueType::F32 => ValueType::F32,
+            EValueType::F64 => ValueType::F64,
+        }
+    }
 
-	pub(crate) fn into_elements(self) -> EValueType {
-		match self {
-			ValueType::I32 => EValueType::I32,
-			ValueType::I64 => EValueType::I64,
-			ValueType::F32 => EValueType::F32,
-			ValueType::F64 => EValueType::F64,
-		}
-	}
+    pub(crate) fn into_elements(self) -> EValueType {
+        match self {
+            ValueType::I32 => EValueType::I32,
+            ValueType::I64 => EValueType::I64,
+            ValueType::F32 => EValueType::F32,
+            ValueType::F64 => EValueType::F64,
+        }
+    }
 }
 
 /// Description of a global variable.
@@ -108,29 +114,29 @@ impl ValueType {
 ///
 /// [`ImportResolver`]: trait.ImportResolver.html
 pub struct GlobalDescriptor {
-	value_type: ValueType,
-	mutable: bool,
+    value_type: ValueType,
+    mutable: bool,
 }
 
 impl GlobalDescriptor {
-	pub(crate) fn from_elements(global_type: &GlobalType) -> GlobalDescriptor {
-		GlobalDescriptor {
-			value_type: ValueType::from_elements(global_type.content_type()),
-			mutable: global_type.is_mutable(),
-		}
-	}
+    pub(crate) fn from_elements(global_type: &GlobalType) -> GlobalDescriptor {
+        GlobalDescriptor {
+            value_type: ValueType::from_elements(global_type.content_type()),
+            mutable: global_type.is_mutable(),
+        }
+    }
 
-	/// Returns [`ValueType`] of the requested global.
-	///
-	/// [`ValueType`]: enum.ValueType.html
-	pub fn value_type(&self) -> ValueType {
-		self.value_type
-	}
+    /// Returns [`ValueType`] of the requested global.
+    ///
+    /// [`ValueType`]: enum.ValueType.html
+    pub fn value_type(&self) -> ValueType {
+        self.value_type
+    }
 
-	/// Returns whether the requested global mutable.
-	pub fn is_mutable(&self) -> bool {
-		self.mutable
-	}
+    /// Returns whether the requested global mutable.
+    pub fn is_mutable(&self) -> bool {
+        self.mutable
+    }
 }
 
 /// Description of a table.
@@ -140,27 +146,27 @@ impl GlobalDescriptor {
 ///
 /// [`ImportResolver`]: trait.ImportResolver.html
 pub struct TableDescriptor {
-	initial: u32,
-	maximum: Option<u32>,
+    initial: u32,
+    maximum: Option<u32>,
 }
 
 impl TableDescriptor {
-	pub(crate) fn from_elements(table_type: &TableType) -> TableDescriptor {
-		TableDescriptor {
-			initial: table_type.limits().initial(),
-			maximum: table_type.limits().maximum(),
-		}
-	}
+    pub(crate) fn from_elements(table_type: &TableType) -> TableDescriptor {
+        TableDescriptor {
+            initial: table_type.limits().initial(),
+            maximum: table_type.limits().maximum(),
+        }
+    }
 
-	/// Returns initial size of the requested table.
-	pub fn initial(&self) -> u32 {
-		self.initial
-	}
+    /// Returns initial size of the requested table.
+    pub fn initial(&self) -> u32 {
+        self.initial
+    }
 
-	/// Returns maximum size of the requested table.
-	pub fn maximum(&self) -> Option<u32> {
-		self.maximum
-	}
+    /// Returns maximum size of the requested table.
+    pub fn maximum(&self) -> Option<u32> {
+        self.maximum
+    }
 }
 
 /// Description of a linear memory.
@@ -170,25 +176,25 @@ impl TableDescriptor {
 ///
 /// [`ImportResolver`]: trait.ImportResolver.html
 pub struct MemoryDescriptor {
-	initial: u32,
-	maximum: Option<u32>,
+    initial: u32,
+    maximum: Option<u32>,
 }
 
 impl MemoryDescriptor {
-	pub(crate) fn from_elements(memory_type: &MemoryType) -> MemoryDescriptor {
-		MemoryDescriptor {
-			initial: memory_type.limits().initial(),
-			maximum: memory_type.limits().maximum(),
-		}
-	}
+    pub(crate) fn from_elements(memory_type: &MemoryType) -> MemoryDescriptor {
+        MemoryDescriptor {
+            initial: memory_type.limits().initial(),
+            maximum: memory_type.limits().maximum(),
+        }
+    }
 
-	/// Returns initial size (in pages) of the requested memory.
-	pub fn initial(&self) -> u32 {
-		self.initial
-	}
+    /// Returns initial size (in pages) of the requested memory.
+    pub fn initial(&self) -> u32 {
+        self.initial
+    }
 
-	/// Returns maximum size (in pages) of the requested memory.
-	pub fn maximum(&self) -> Option<u32> {
-		self.maximum
-	}
+    /// Returns maximum size (in pages) of the requested memory.
+    pub fn maximum(&self) -> Option<u32> {
+        self.maximum
+    }
 }

src/validation/context.rs

@@ -1,134 +0,0 @@
-use parity_wasm::elements::{MemoryType, TableType, GlobalType, BlockType, ValueType, FunctionType};
-use validation::Error;
-
-#[derive(Default, Debug)]
-pub struct ModuleContext {
-	pub memories: Vec<MemoryType>,
-	pub tables: Vec<TableType>,
-	pub globals: Vec<GlobalType>,
-	pub types: Vec<FunctionType>,
-	pub func_type_indexes: Vec<u32>,
-}
-
-impl ModuleContext {
-	pub fn memories(&self) -> &[MemoryType] {
-		&self.memories
-	}
-
-	pub fn tables(&self) -> &[TableType] {
-		&self.tables
-	}
-
-	pub fn globals(&self) -> &[GlobalType] {
-		&self.globals
-	}
-
-	pub fn types(&self) -> &[FunctionType] {
-		&self.types
-	}
-
-	pub fn func_type_indexes(&self) -> &[u32] {
-		&self.func_type_indexes
-	}
-
-	pub fn require_memory(&self, idx: u32) -> Result<(), Error> {
-		if self.memories().get(idx as usize).is_none() {
-			return Err(Error(format!("Memory at index {} doesn't exists", idx)));
-		}
-		Ok(())
-	}
-
-	pub fn require_table(&self, idx: u32) -> Result<&TableType, Error> {
-		self.tables()
-			.get(idx as usize)
-			.ok_or_else(|| Error(format!("Table at index {} doesn't exists", idx)))
-	}
-
-	pub fn require_function(&self, idx: u32) -> Result<(&[ValueType], BlockType), Error> {
-		let ty_idx = self.func_type_indexes()
-			.get(idx as usize)
-			.ok_or_else(|| Error(format!("Function at index {} doesn't exists", idx)))?;
-		self.require_function_type(*ty_idx)
-	}
-
-	pub fn require_function_type(&self, idx: u32) -> Result<(&[ValueType], BlockType), Error> {
-		let ty = self.types()
-			.get(idx as usize)
-			.ok_or_else(|| Error(format!("Type at index {} doesn't exists", idx)))?;
-
-		let params = ty.params();
-		let return_ty = ty.return_type()
-			.map(BlockType::Value)
-			.unwrap_or(BlockType::NoResult);
-		Ok((params, return_ty))
-	}
-
-	pub fn require_global(&self, idx: u32, mutability: Option<bool>) -> Result<&GlobalType, Error> {
-		let global = self.globals()
-			.get(idx as usize)
-			.ok_or_else(|| Error(format!("Global at index {} doesn't exists", idx)))?;
-
-		if let Some(expected_mutable) = mutability {
-			if expected_mutable && !global.is_mutable() {
-				return Err(Error(format!("Expected global {} to be mutable", idx)));
-			}
-			if !expected_mutable && global.is_mutable() {
-				return Err(Error(format!("Expected global {} to be immutable", idx)));
-			}
-		}
-		Ok(global)
-	}
-}
-
-#[derive(Default)]
-pub struct ModuleContextBuilder {
-	memories: Vec<MemoryType>,
-	tables: Vec<TableType>,
-	globals: Vec<GlobalType>,
-	types: Vec<FunctionType>,
-	func_type_indexes: Vec<u32>,
-}
-
-impl ModuleContextBuilder {
-	pub fn new() -> ModuleContextBuilder {
-		ModuleContextBuilder::default()
-	}
-
-	pub fn push_memory(&mut self, memory: MemoryType) {
-		self.memories.push(memory);
-	}
-
-	pub fn push_table(&mut self, table: TableType) {
-		self.tables.push(table);
-	}
-
-	pub fn push_global(&mut self, global: GlobalType) {
-		self.globals.push(global);
-	}
-
-	pub fn set_types(&mut self, types: Vec<FunctionType>) {
-		self.types = types;
-	}
-
-	pub fn push_func_type_index(&mut self, func_type_index: u32) {
-		self.func_type_indexes.push(func_type_index);
-	}
-
-	pub fn build(self) -> ModuleContext {
-		let ModuleContextBuilder {
-			memories,
-			tables,
-			globals,
-			types,
-			func_type_indexes,
-		} = self;
-
-		ModuleContext {
-			memories,
-			tables,
-			globals,
-			types,
-			func_type_indexes,
-		}
-	}
-}

src/validation/func.rs

@@ -1,754 +0,0 @@
-use std::u32;
-use std::collections::HashMap;
-use parity_wasm::elements::{Opcode, BlockType, ValueType, TableElementType, Func, FuncBody};
-use common::{DEFAULT_MEMORY_INDEX, DEFAULT_TABLE_INDEX};
-use validation::context::ModuleContext;
-
-use validation::Error;
-use validation::util::Locals;
-
-use common::stack::StackWithLimit;
-use common::{BlockFrame, BlockFrameType};
-
-/// Maximum number of entries in value stack per function.
-const DEFAULT_VALUE_STACK_LIMIT: usize = 16384;
-/// Maximum number of entries in frame stack per function.
-const DEFAULT_FRAME_STACK_LIMIT: usize = 16384;
-
-/// Function validation context.
-struct FunctionValidationContext<'a> {
-	/// Wasm module
-	module: &'a ModuleContext,
-	/// Current instruction position.
-	position: usize,
-	/// Local variables.
-	locals: Locals<'a>,
-	/// Value stack.
-	value_stack: StackWithLimit<StackValueType>,
-	/// Frame stack.
-	frame_stack: StackWithLimit<BlockFrame>,
-	/// Function return type. None if validating expression.
-	return_type: Option<BlockType>,
-	/// Labels positions.
-	labels: HashMap<usize, usize>,
-}
-
-/// Value type on the stack.
-#[derive(Debug, Clone, Copy)]
-enum StackValueType {
-	/// Any value type.
-	Any,
-	/// Concrete value type.
-	Specific(ValueType),
-}
-
-/// Function validator.
-pub struct Validator;
-
-/// Instruction outcome.
-#[derive(Debug, Clone)]
-enum InstructionOutcome {
-	/// Continue with next instruction.
-	ValidateNextInstruction,
-	/// Unreachable instruction reached.
-	Unreachable,
-}
-
-impl Validator {
-	pub fn validate_function(
-		module: &ModuleContext,
-		func: &Func,
-		body: &FuncBody,
-	) -> Result<HashMap<usize, usize>, Error> {
-		let (params, result_ty) = module.require_function_type(func.type_ref())?;
-
-		let mut context = FunctionValidationContext::new(
-			&module,
-			Locals::new(params, body.locals()),
-			DEFAULT_VALUE_STACK_LIMIT,
-			DEFAULT_FRAME_STACK_LIMIT,
-			result_ty,
-		);
-
-		context.push_label(BlockFrameType::Function, result_ty)?;
-		Validator::validate_function_block(&mut context, body.code().elements())?;
-		while !context.frame_stack.is_empty() {
-			context.pop_label()?;
-		}
-
-		Ok(context.into_labels())
-	}
-
-	fn validate_function_block(context: &mut FunctionValidationContext, body: &[Opcode]) -> Result<(), Error> {
-		let body_len = body.len();
-		if body_len == 0 {
-			return Err(Error("Non-empty function body expected".into()));
-		}
-
-		loop {
-			let opcode = &body[context.position];
-			match Validator::validate_instruction(context, opcode)? {
-				InstructionOutcome::ValidateNextInstruction => (),
-				InstructionOutcome::Unreachable => context.unreachable()?,
-			}
-
-			context.position += 1;
-			if context.position == body_len {
-				return Ok(());
-			}
-		}
-	}
-
-	fn validate_instruction(context: &mut FunctionValidationContext, opcode: &Opcode) -> Result<InstructionOutcome, Error> {
-		use self::Opcode::*;
-		match *opcode {
-			Unreachable => Ok(InstructionOutcome::Unreachable),
-			Nop => Ok(InstructionOutcome::ValidateNextInstruction),
-			Block(block_type) => Validator::validate_block(context, block_type),
-			Loop(block_type) => Validator::validate_loop(context, block_type),
-			If(block_type) => Validator::validate_if(context, block_type),
-			Else => Validator::validate_else(context),
-			End => Validator::validate_end(context),
-			Br(idx) => Validator::validate_br(context, idx),
-			BrIf(idx) => Validator::validate_br_if(context, idx),
-			BrTable(ref table, default) => Validator::validate_br_table(context, table, default),
-			Return => Validator::validate_return(context),
-
-			Call(index) => Validator::validate_call(context, index),
-			CallIndirect(index, _reserved) => Validator::validate_call_indirect(context, index),
-
-			Drop => Validator::validate_drop(context),
-			Select => Validator::validate_select(context),
-
-			GetLocal(index) => Validator::validate_get_local(context, index),
-			SetLocal(index) => Validator::validate_set_local(context, index),
-			TeeLocal(index) => Validator::validate_tee_local(context, index),
-			GetGlobal(index) => Validator::validate_get_global(context, index),
-			SetGlobal(index) => Validator::validate_set_global(context, index),
-
-			I32Load(align, _) => Validator::validate_load(context, align, 4, ValueType::I32),
-			I64Load(align, _) => Validator::validate_load(context, align, 8, ValueType::I64),
-			F32Load(align, _) => Validator::validate_load(context, align, 4, ValueType::F32),
-			F64Load(align, _) => Validator::validate_load(context, align, 8, ValueType::F64),
-			I32Load8S(align, _) => Validator::validate_load(context, align, 1, ValueType::I32),
-			I32Load8U(align, _) => Validator::validate_load(context, align, 1, ValueType::I32),
-			I32Load16S(align, _) => Validator::validate_load(context, align, 2, ValueType::I32),
-			I32Load16U(align, _) => Validator::validate_load(context, align, 2, ValueType::I32),
-			I64Load8S(align, _) => Validator::validate_load(context, align, 1, ValueType::I64),
-			I64Load8U(align, _) => Validator::validate_load(context, align, 1, ValueType::I64),
-			I64Load16S(align, _) => Validator::validate_load(context, align, 2, ValueType::I64),
-			I64Load16U(align, _) => Validator::validate_load(context, align, 2, ValueType::I64),
-			I64Load32S(align, _) => Validator::validate_load(context, align, 4, ValueType::I64),
-			I64Load32U(align, _) => Validator::validate_load(context, align, 4, ValueType::I64),
-
-			I32Store(align, _) => Validator::validate_store(context, align, 4, ValueType::I32),
-			I64Store(align, _) => Validator::validate_store(context, align, 8, ValueType::I64),
-			F32Store(align, _) => Validator::validate_store(context, align, 4, ValueType::F32),
-			F64Store(align, _) => Validator::validate_store(context, align, 8, ValueType::F64),
-			I32Store8(align, _) => Validator::validate_store(context, align, 1, ValueType::I32),
-			I32Store16(align, _) => Validator::validate_store(context, align, 2, ValueType::I32),
-			I64Store8(align, _) => Validator::validate_store(context, align, 1, ValueType::I64),
-			I64Store16(align, _) => Validator::validate_store(context, align, 2, ValueType::I64),
-			I64Store32(align, _) => Validator::validate_store(context, align, 4, ValueType::I64),
-
-			CurrentMemory(_) => Validator::validate_current_memory(context),
-			GrowMemory(_) => Validator::validate_grow_memory(context),
-
-			I32Const(_) => Validator::validate_const(context, ValueType::I32),
-			I64Const(_) => Validator::validate_const(context, ValueType::I64),
-			F32Const(_) => Validator::validate_const(context, ValueType::F32),
-			F64Const(_) => Validator::validate_const(context, ValueType::F64),
-
-			I32Eqz => Validator::validate_testop(context, ValueType::I32),
-			I32Eq => Validator::validate_relop(context, ValueType::I32),
-			I32Ne => Validator::validate_relop(context, ValueType::I32),
-			I32LtS => Validator::validate_relop(context, ValueType::I32),
-			I32LtU => Validator::validate_relop(context, ValueType::I32),
-			I32GtS => Validator::validate_relop(context, ValueType::I32),
-			I32GtU => Validator::validate_relop(context, ValueType::I32),
-			I32LeS => Validator::validate_relop(context, ValueType::I32),
-			I32LeU => Validator::validate_relop(context, ValueType::I32),
-			I32GeS => Validator::validate_relop(context, ValueType::I32),
-			I32GeU => Validator::validate_relop(context, ValueType::I32),
-
-			I64Eqz => Validator::validate_testop(context, ValueType::I64),
-			I64Eq => Validator::validate_relop(context, ValueType::I64),
-			I64Ne => Validator::validate_relop(context, ValueType::I64),
-			I64LtS => Validator::validate_relop(context, ValueType::I64),
-			I64LtU => Validator::validate_relop(context, ValueType::I64),
-			I64GtS => Validator::validate_relop(context, ValueType::I64),
-			I64GtU => Validator::validate_relop(context, ValueType::I64),
-			I64LeS => Validator::validate_relop(context, ValueType::I64),
-			I64LeU => Validator::validate_relop(context, ValueType::I64),
-			I64GeS => Validator::validate_relop(context, ValueType::I64),
-			I64GeU => Validator::validate_relop(context, ValueType::I64),
-
-			F32Eq => Validator::validate_relop(context, ValueType::F32),
-			F32Ne => Validator::validate_relop(context, ValueType::F32),
-			F32Lt => Validator::validate_relop(context, ValueType::F32),
-			F32Gt => Validator::validate_relop(context, ValueType::F32),
-			F32Le => Validator::validate_relop(context, ValueType::F32),
-			F32Ge => Validator::validate_relop(context, ValueType::F32),
-
-			F64Eq => Validator::validate_relop(context, ValueType::F64),
-			F64Ne => Validator::validate_relop(context, ValueType::F64),
-			F64Lt => Validator::validate_relop(context, ValueType::F64),
-			F64Gt => Validator::validate_relop(context, ValueType::F64),
-			F64Le => Validator::validate_relop(context, ValueType::F64),
-			F64Ge => Validator::validate_relop(context, ValueType::F64),
-
-			I32Clz => Validator::validate_unop(context, ValueType::I32),
-			I32Ctz => Validator::validate_unop(context, ValueType::I32),
-			I32Popcnt => Validator::validate_unop(context, ValueType::I32),
-			I32Add => Validator::validate_binop(context, ValueType::I32),
-			I32Sub => Validator::validate_binop(context, ValueType::I32),
-			I32Mul => Validator::validate_binop(context, ValueType::I32),
-			I32DivS => Validator::validate_binop(context, ValueType::I32),
-			I32DivU => Validator::validate_binop(context, ValueType::I32),
-			I32RemS => Validator::validate_binop(context, ValueType::I32),
-			I32RemU => Validator::validate_binop(context, ValueType::I32),
-			I32And => Validator::validate_binop(context, ValueType::I32),
-			I32Or => Validator::validate_binop(context, ValueType::I32),
-			I32Xor => Validator::validate_binop(context, ValueType::I32),
-			I32Shl => Validator::validate_binop(context, ValueType::I32),
-			I32ShrS => Validator::validate_binop(context, ValueType::I32),
-			I32ShrU => Validator::validate_binop(context, ValueType::I32),
-			I32Rotl => Validator::validate_binop(context, ValueType::I32),
-			I32Rotr => Validator::validate_binop(context, ValueType::I32),
-
-			I64Clz => Validator::validate_unop(context, ValueType::I64),
-			I64Ctz => Validator::validate_unop(context, ValueType::I64),
-			I64Popcnt => Validator::validate_unop(context, ValueType::I64),
-			I64Add => Validator::validate_binop(context, ValueType::I64),
-			I64Sub => Validator::validate_binop(context, ValueType::I64),
-			I64Mul => Validator::validate_binop(context, ValueType::I64),
-			I64DivS => Validator::validate_binop(context, ValueType::I64),
-			I64DivU => Validator::validate_binop(context, ValueType::I64),
-			I64RemS => Validator::validate_binop(context, ValueType::I64),
-			I64RemU => Validator::validate_binop(context, ValueType::I64),
-			I64And => Validator::validate_binop(context, ValueType::I64),
-			I64Or => Validator::validate_binop(context, ValueType::I64),
-			I64Xor => Validator::validate_binop(context, ValueType::I64),
-			I64Shl => Validator::validate_binop(context, ValueType::I64),
-			I64ShrS => Validator::validate_binop(context, ValueType::I64),
-			I64ShrU => Validator::validate_binop(context, ValueType::I64),
-			I64Rotl => Validator::validate_binop(context, ValueType::I64),
-			I64Rotr => Validator::validate_binop(context, ValueType::I64),
-
-			F32Abs => Validator::validate_unop(context, ValueType::F32),
-			F32Neg => Validator::validate_unop(context, ValueType::F32),
-			F32Ceil => Validator::validate_unop(context, ValueType::F32),
-			F32Floor => Validator::validate_unop(context, ValueType::F32),
-			F32Trunc => Validator::validate_unop(context, ValueType::F32),
-			F32Nearest => Validator::validate_unop(context, ValueType::F32),
-			F32Sqrt => Validator::validate_unop(context, ValueType::F32),
-			F32Add => Validator::validate_binop(context, ValueType::F32),
-			F32Sub => Validator::validate_binop(context, ValueType::F32),
-			F32Mul => Validator::validate_binop(context, ValueType::F32),
-			F32Div => Validator::validate_binop(context, ValueType::F32),
-			F32Min => Validator::validate_binop(context, ValueType::F32),
-			F32Max => Validator::validate_binop(context, ValueType::F32),
-			F32Copysign => Validator::validate_binop(context, ValueType::F32),
-
-			F64Abs => Validator::validate_unop(context, ValueType::F64),
-			F64Neg => Validator::validate_unop(context, ValueType::F64),
-			F64Ceil => Validator::validate_unop(context, ValueType::F64),
-			F64Floor => Validator::validate_unop(context, ValueType::F64),
-			F64Trunc => Validator::validate_unop(context, ValueType::F64),
-			F64Nearest => Validator::validate_unop(context, ValueType::F64),
-			F64Sqrt => Validator::validate_unop(context, ValueType::F64),
-			F64Add => Validator::validate_binop(context, ValueType::F64),
-			F64Sub => Validator::validate_binop(context, ValueType::F64),
-			F64Mul => Validator::validate_binop(context, ValueType::F64),
-			F64Div => Validator::validate_binop(context, ValueType::F64),
-			F64Min => Validator::validate_binop(context, ValueType::F64),
-			F64Max => Validator::validate_binop(context, ValueType::F64),
-			F64Copysign => Validator::validate_binop(context, ValueType::F64),
-
-			I32WrapI64 => Validator::validate_cvtop(context, ValueType::I64, ValueType::I32),
-			I32TruncSF32 => Validator::validate_cvtop(context, ValueType::F32, ValueType::I32),
-			I32TruncUF32 => Validator::validate_cvtop(context, ValueType::F32, ValueType::I32),
-			I32TruncSF64 => Validator::validate_cvtop(context, ValueType::F64, ValueType::I32),
-			I32TruncUF64 => Validator::validate_cvtop(context, ValueType::F64, ValueType::I32),
-			I64ExtendSI32 => Validator::validate_cvtop(context, ValueType::I32, ValueType::I64),
-			I64ExtendUI32 => Validator::validate_cvtop(context, ValueType::I32, ValueType::I64),
-			I64TruncSF32 => Validator::validate_cvtop(context, ValueType::F32, ValueType::I64),
-			I64TruncUF32 => Validator::validate_cvtop(context, ValueType::F32, ValueType::I64),
-			I64TruncSF64 => Validator::validate_cvtop(context, ValueType::F64, ValueType::I64),
-			I64TruncUF64 => Validator::validate_cvtop(context, ValueType::F64, ValueType::I64),
-			F32ConvertSI32 => Validator::validate_cvtop(context, ValueType::I32, ValueType::F32),
-			F32ConvertUI32 => Validator::validate_cvtop(context, ValueType::I32, ValueType::F32),
-			F32ConvertSI64 => Validator::validate_cvtop(context, ValueType::I64, ValueType::F32),
-			F32ConvertUI64 => Validator::validate_cvtop(context, ValueType::I64, ValueType::F32),
-			F32DemoteF64 => Validator::validate_cvtop(context, ValueType::F64, ValueType::F32),
-			F64ConvertSI32 => Validator::validate_cvtop(context, ValueType::I32, ValueType::F64),
-			F64ConvertUI32 => Validator::validate_cvtop(context, ValueType::I32, ValueType::F64),
-			F64ConvertSI64 => Validator::validate_cvtop(context, ValueType::I64, ValueType::F64),
-			F64ConvertUI64 => Validator::validate_cvtop(context, ValueType::I64, ValueType::F64),
-			F64PromoteF32 => Validator::validate_cvtop(context, ValueType::F32, ValueType::F64),
-
-			I32ReinterpretF32 => Validator::validate_cvtop(context, ValueType::F32, ValueType::I32),
-			I64ReinterpretF64 => Validator::validate_cvtop(context, ValueType::F64, ValueType::I64),
-			F32ReinterpretI32 => Validator::validate_cvtop(context, ValueType::I32, ValueType::F32),
-			F64ReinterpretI64 => Validator::validate_cvtop(context, ValueType::I64, ValueType::F64),
-		}
-	}
-
-	fn validate_const(context: &mut FunctionValidationContext, value_type: ValueType) -> Result<InstructionOutcome, Error> {
-		context.push_value(value_type.into())?;
-		Ok(InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_unop(context: &mut FunctionValidationContext, value_type: ValueType) -> Result<InstructionOutcome, Error> {
-		context.pop_value(value_type.into())?;
-		context.push_value(value_type.into())?;
-		Ok(InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_binop(context: &mut FunctionValidationContext, value_type: ValueType) -> Result<InstructionOutcome, Error> {
-		context.pop_value(value_type.into())?;
-		context.pop_value(value_type.into())?;
-		context.push_value(value_type.into())?;
-		Ok(InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_testop(context: &mut FunctionValidationContext, value_type: ValueType) -> Result<InstructionOutcome, Error> {
-		context.pop_value(value_type.into())?;
-		context.push_value(ValueType::I32.into())?;
-		Ok(InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_relop(context: &mut FunctionValidationContext, value_type: ValueType) -> Result<InstructionOutcome, Error> {
-		context.pop_value(value_type.into())?;
-		context.pop_value(value_type.into())?;
-		context.push_value(ValueType::I32.into())?;
-		Ok(InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_cvtop(context: &mut FunctionValidationContext, value_type1: ValueType, value_type2: ValueType) -> Result<InstructionOutcome, Error> {
-		context.pop_value(value_type1.into())?;
-		context.push_value(value_type2.into())?;
-		Ok(InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_drop(context: &mut FunctionValidationContext) -> Result<InstructionOutcome, Error> {
-		context.pop_value(StackValueType::Any).map(|_| ())?;
-		Ok(InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_select(context: &mut FunctionValidationContext) -> Result<InstructionOutcome, Error> {
-		context.pop_value(ValueType::I32.into())?;
-		let select_type = context.pop_value(StackValueType::Any)?;
-		context.pop_value(select_type)?;
-		context.push_value(select_type)?;
-		Ok(InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_get_local(context: &mut FunctionValidationContext, index: u32) -> Result<InstructionOutcome, Error> {
-		let local_type = context.require_local(index)?;
-		context.push_value(local_type)?;
-		Ok(InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_set_local(context: &mut FunctionValidationContext, index: u32) -> Result<InstructionOutcome, Error> {
-		let local_type = context.require_local(index)?;
-		let value_type = context.pop_value(StackValueType::Any)?;
-		if local_type != value_type {
-			return Err(Error(format!("Trying to update local {} of type {:?} with value of type {:?}", index, local_type, value_type)));
-		}
-		Ok(InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_tee_local(context: &mut FunctionValidationContext, index: u32) -> Result<InstructionOutcome, Error> {
-		let local_type = context.require_local(index)?;
-		context.tee_value(local_type)?;
-		Ok(InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_get_global(context: &mut FunctionValidationContext, index: u32) -> Result<InstructionOutcome, Error> {
-		let global_type: StackValueType = {
-			let global = context.module.require_global(index, None)?;
-			global.content_type().into()
-		};
-		context.push_value(global_type)?;
-		Ok(InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_set_global(context: &mut FunctionValidationContext, index: u32) -> Result<InstructionOutcome, Error> {
-		let global_type: StackValueType = {
-			let global = context.module.require_global(index, Some(true))?;
-			global.content_type().into()
-		};
-		let value_type = context.pop_value(StackValueType::Any)?;
-		if global_type != value_type {
-			return Err(Error(format!("Trying to update global {} of type {:?} with value of type {:?}", index, global_type, value_type)));
-		}
-		Ok(InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_load(context: &mut FunctionValidationContext, align: u32, max_align: u32, value_type: ValueType) -> Result<InstructionOutcome, Error> {
-		if 1u32.checked_shl(align).unwrap_or(u32::MAX) > max_align {
-			return Err(Error(format!("Too large memory alignment 2^{} (expected at most {})", align, max_align)));
-		}
-
-		context.pop_value(ValueType::I32.into())?;
-		context.module.require_memory(DEFAULT_MEMORY_INDEX)?;
-		context.push_value(value_type.into())?;
-		Ok(InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_store(context: &mut FunctionValidationContext, align: u32, max_align: u32, value_type: ValueType) -> Result<InstructionOutcome, Error> {
-		if 1u32.checked_shl(align).unwrap_or(u32::MAX) > max_align {
-			return Err(Error(format!("Too large memory alignment 2^{} (expected at most {})", align, max_align)));
-		}
-
-		context.module.require_memory(DEFAULT_MEMORY_INDEX)?;
-		context.pop_value(value_type.into())?;
-		context.pop_value(ValueType::I32.into())?;
-		Ok(InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_block(context: &mut FunctionValidationContext, block_type: BlockType) -> Result<InstructionOutcome, Error> {
-		context.push_label(BlockFrameType::Block, block_type).map(|_| InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_loop(context: &mut FunctionValidationContext, block_type: BlockType) -> Result<InstructionOutcome, Error> {
-		context.push_label(BlockFrameType::Loop, block_type).map(|_| InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_if(context: &mut FunctionValidationContext, block_type: BlockType) -> Result<InstructionOutcome, Error> {
-		context.pop_value(ValueType::I32.into())?;
-		context.push_label(BlockFrameType::IfTrue, block_type).map(|_| InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_else(context: &mut FunctionValidationContext) -> Result<InstructionOutcome, Error> {
-		let block_type = {
-			let top_frame = context.top_label()?;
-			if top_frame.frame_type != BlockFrameType::IfTrue {
-				return Err(Error("Misplaced else instruction".into()));
-			}
-			top_frame.block_type
-		};
-		context.pop_label()?;
-
-		if let BlockType::Value(value_type) = block_type {
-			context.pop_value(value_type.into())?;
-		}
-		context.push_label(BlockFrameType::IfFalse, block_type).map(|_| InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_end(context: &mut FunctionValidationContext) -> Result<InstructionOutcome, Error> {
-		{
-			let top_frame = context.top_label()?;
-			if top_frame.frame_type == BlockFrameType::IfTrue {
-				if top_frame.block_type != BlockType::NoResult {
-					return Err(Error(format!("If block without else required to have NoResult block type. But it have {:?} type", top_frame.block_type)));
-				}
-			}
-		}
-
-		context.pop_label().map(|_| InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_br(context: &mut FunctionValidationContext, idx: u32) -> Result<InstructionOutcome, Error> {
-		let (frame_type, frame_block_type) = {
-			let frame = context.require_label(idx)?;
-			(frame.frame_type, frame.block_type)
-		};
-		if frame_type != BlockFrameType::Loop {
-			if let BlockType::Value(value_type) = frame_block_type {
-				context.tee_value(value_type.into())?;
-			}
-		}
-		Ok(InstructionOutcome::Unreachable)
-	}
-
-	fn validate_br_if(context: &mut FunctionValidationContext, idx: u32) -> Result<InstructionOutcome, Error> {
-		context.pop_value(ValueType::I32.into())?;
-
-		let (frame_type, frame_block_type) = {
-			let frame = context.require_label(idx)?;
-			(frame.frame_type, frame.block_type)
-		};
-		if frame_type != BlockFrameType::Loop {
-			if let BlockType::Value(value_type) = frame_block_type {
-				context.tee_value(value_type.into())?;
-			}
-		}
-		Ok(InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_br_table(context: &mut FunctionValidationContext, table: &[u32], default: u32) -> Result<InstructionOutcome, Error> {
-		let required_block_type: BlockType = {
-			let default_block = context.require_label(default)?;
-			let required_block_type = if default_block.frame_type != BlockFrameType::Loop {
-				default_block.block_type
-			} else {
-				BlockType::NoResult
-			};
-
-			for label in table {
-				let label_block = context.require_label(*label)?;
-				let label_block_type = if label_block.frame_type != BlockFrameType::Loop {
-					label_block.block_type
-				} else {
-					BlockType::NoResult
-				};
-				if required_block_type != label_block_type {
-					return Err(
-						Error(
-							format!(
-								"Labels in br_table points to block of different types: {:?} and {:?}",
-								required_block_type,
-								label_block.block_type
-							)
-						)
-					);
-				}
-			}
-			required_block_type
-		};
-
-		context.pop_value(ValueType::I32.into())?;
-		if let BlockType::Value(value_type) = required_block_type {
-			context.tee_value(value_type.into())?;
-		}
-
-		Ok(InstructionOutcome::Unreachable)
-	}
-
-	fn validate_return(context: &mut FunctionValidationContext) -> Result<InstructionOutcome, Error> {
-		if let BlockType::Value(value_type) = context.return_type()? {
-			context.tee_value(value_type.into())?;
-		}
-		Ok(InstructionOutcome::Unreachable)
-	}
-
-	fn validate_call(context: &mut FunctionValidationContext, idx: u32) -> Result<InstructionOutcome, Error> {
-		let (argument_types, return_type) = context.module.require_function(idx)?;
-		for argument_type in argument_types.iter().rev() {
-			context.pop_value((*argument_type).into())?;
-		}
-		if let BlockType::Value(value_type) = return_type {
-			context.push_value(value_type.into())?;
-		}
-		Ok(InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_call_indirect(context: &mut FunctionValidationContext, idx: u32) -> Result<InstructionOutcome, Error> {
-		{
-			let table = context.module.require_table(DEFAULT_TABLE_INDEX)?;
-			if table.elem_type() != TableElementType::AnyFunc {
-				return Err(Error(format!(
-					"Table {} has element type {:?} while `anyfunc` expected",
-					idx,
-					table.elem_type()
-				)));
-			}
-		}
-
-		context.pop_value(ValueType::I32.into())?;
-		let (argument_types, return_type) = context.module.require_function_type(idx)?;
-		for argument_type in argument_types.iter().rev() {
-			context.pop_value((*argument_type).into())?;
-		}
-		if let BlockType::Value(value_type) = return_type {
-			context.push_value(value_type.into())?;
-		}
-		Ok(InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_current_memory(context: &mut FunctionValidationContext) -> Result<InstructionOutcome, Error> {
-		context.module.require_memory(DEFAULT_MEMORY_INDEX)?;
-		context.push_value(ValueType::I32.into())?;
-		Ok(InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn validate_grow_memory(context: &mut FunctionValidationContext) -> Result<InstructionOutcome, Error> {
-		context.module.require_memory(DEFAULT_MEMORY_INDEX)?;
-		context.pop_value(ValueType::I32.into())?;
-		context.push_value(ValueType::I32.into())?;
-		Ok(InstructionOutcome::ValidateNextInstruction)
-	}
-}
-
-impl<'a> FunctionValidationContext<'a> {
-	fn new(
-		module: &'a ModuleContext,
-		locals: Locals<'a>,
-		value_stack_limit: usize,
-		frame_stack_limit: usize,
-		return_type: BlockType,
-	) -> Self {
-		FunctionValidationContext {
-			module: module,
-			position: 0,
-			locals: locals,
-			value_stack: StackWithLimit::with_limit(value_stack_limit),
-			frame_stack: StackWithLimit::with_limit(frame_stack_limit),
-			return_type: Some(return_type),
-			labels: HashMap::new(),
-		}
-	}
-
-	fn push_value(&mut self, value_type: StackValueType) -> Result<(), Error> {
-		Ok(self.value_stack.push(value_type.into())?)
-	}
-
-	fn pop_value(&mut self, value_type: StackValueType) -> Result<StackValueType, Error> {
-		let (is_stack_polymorphic, label_value_stack_len) = {
-			let frame = self.top_label()?;
-			(frame.polymorphic_stack, frame.value_stack_len)
-		};
-		let stack_is_empty = self.value_stack.len() == label_value_stack_len;
-		let actual_value = if stack_is_empty && is_stack_polymorphic {
-			StackValueType::Any
-		} else {
-			self.check_stack_access()?;
-			self.value_stack.pop()?
-		};
-		match actual_value {
-			StackValueType::Specific(stack_value_type) if stack_value_type == value_type => {
-				Ok(actual_value)
-			}
-			StackValueType::Any => Ok(actual_value),
-			stack_value_type @ _ => Err(Error(format!(
-				"Expected value of type {:?} on top of stack. Got {:?}",
-				value_type, stack_value_type
-			))),
-		}
-	}
-
-	fn check_stack_access(&self) -> Result<(), Error> {
-		let value_stack_min = self.frame_stack.top().expect("at least 1 topmost block").value_stack_len;
-		if self.value_stack.len() > value_stack_min {
-			Ok(())
-		} else {
-			Err(Error("Trying to access parent frame stack values.".into()))
-		}
-	}
-
-	fn tee_value(&mut self, value_type: StackValueType) -> Result<(), Error> {
-		let _ = self.pop_value(value_type)?;
-		self.push_value(value_type)?;
-		Ok(())
-	}
-
-	fn unreachable(&mut self) -> Result<(), Error> {
-		let frame = self.frame_stack.top_mut()?;
-		self.value_stack.resize(frame.value_stack_len, StackValueType::Any);
-		frame.polymorphic_stack = true;
-		Ok(())
-	}
-
-	fn top_label(&self) -> Result<&BlockFrame, Error> {
-		Ok(self.frame_stack.top()?)
-	}
-
-	fn push_label(&mut self, frame_type: BlockFrameType, block_type: BlockType) -> Result<(), Error> {
-		Ok(self.frame_stack.push(BlockFrame {
-			frame_type: frame_type,
-			block_type: block_type,
-			begin_position: self.position,
-			branch_position: self.position,
-			end_position: self.position,
-			value_stack_len: self.value_stack.len(),
-			polymorphic_stack: false,
-		})?)
-	}
-
-	fn pop_label(&mut self) -> Result<InstructionOutcome, Error> {
-		// Don't pop frame yet. This is essential since we still might pop values from the value stack
-		// and this in turn requires current frame to check whether or not we've reached
-		// unreachable.
-		let block_type = self.frame_stack.top()?.block_type;
-		match block_type {
-			BlockType::NoResult => (),
-			BlockType::Value(required_value_type) => {
-				self.pop_value(StackValueType::Specific(required_value_type))?;
-			}
-		}
-
-		let frame = self.frame_stack.pop()?;
-		if self.value_stack.len() != frame.value_stack_len {
-			return Err(Error(format!(
-				"Unexpected stack height {}, expected {}",
-				self.value_stack.len(),
-				frame.value_stack_len
-			)));
-		}
-
-		if !self.frame_stack.is_empty() {
-			self.labels.insert(frame.begin_position, self.position);
-		}
-		if let BlockType::Value(value_type) = frame.block_type {
-			self.push_value(value_type.into())?;
-		}
-
-		Ok(InstructionOutcome::ValidateNextInstruction)
-	}
-
-	fn require_label(&self, idx: u32) -> Result<&BlockFrame, Error> {
-		Ok(self.frame_stack.get(idx as usize)?)
-	}
-
-	fn return_type(&self) -> Result<BlockType, Error> {
-		self.return_type.ok_or(Error("Trying to return from expression".into()))
-	}
-
-	fn require_local(&self, idx: u32) -> Result<StackValueType, Error> {
-		Ok(self.locals.type_of_local(idx).map(StackValueType::from)?)
-	}
-
-	fn into_labels(self) -> HashMap<usize, usize> {
-		self.labels
-	}
-}
-
-impl StackValueType {
-	fn is_any(&self) -> bool {
-		match self {
-			&StackValueType::Any => true,
-			_ => false,
-		}
-	}
-
-	fn value_type(&self) -> ValueType {
-		match self {
-			&StackValueType::Any => unreachable!("must be checked by caller"),
-			&StackValueType::Specific(value_type) => value_type,
-		}
-	}
-}
-
-impl From<ValueType> for StackValueType {
-	fn from(value_type: ValueType) -> Self {
-		StackValueType::Specific(value_type)
-	}
-}
-
-impl PartialEq<StackValueType> for StackValueType {
-	fn eq(&self, other: &StackValueType) -> bool {
-		if self.is_any() || other.is_any() {
-			true
-		} else {
-			self.value_type() == other.value_type()
-		}
-	}
-}
-
-impl PartialEq<ValueType> for StackValueType {
-	fn eq(&self, other: &ValueType) -> bool {
-		if self.is_any() {
-			true
-		} else {
-			self.value_type() == *other
-		}
-	}
-}
-
-impl PartialEq<StackValueType> for ValueType {
-	fn eq(&self, other: &StackValueType) -> bool {
-		other == self
-	}
-}

src/validation/mod.rs

@@ -1,451 +0,0 @@
-use std::error;
-use std::fmt;
-use std::collections::{HashMap, HashSet};
-use parity_wasm::elements::{
-	BlockType, External, GlobalEntry, GlobalType, Internal, MemoryType, Module, Opcode,
-	ResizableLimits, TableType, ValueType, InitExpr, Type
-};
-use common::stack;
-use self::context::ModuleContextBuilder;
-use self::func::Validator;
-use memory_units::Pages;
-
-mod context;
-mod func;
-mod util;
-
-#[cfg(test)]
-mod tests;
-
-#[derive(Debug)]
-pub struct Error(String);
-
-impl fmt::Display for Error {
-	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-		write!(f, "{}", self.0)
-	}
-}
-
-impl error::Error for Error {
-	fn description(&self) -> &str {
-		&self.0
-	}
-}
-
-impl From<stack::Error> for Error {
-	fn from(e: stack::Error) -> Error {
-		Error(format!("Stack: {}", e))
-	}
-}
-
-#[derive(Clone)]
-pub struct ValidatedModule {
-	pub labels: HashMap<usize, HashMap<usize, usize>>,
-	pub module: Module,
-}
-
-impl ::std::ops::Deref for ValidatedModule {
-	type Target = Module;
-	fn deref(&self) -> &Module {
-		&self.module
-	}
-}
-
-pub fn deny_floating_point(module: &Module) -> Result<(), Error> {
-	if let Some(code) = module.code_section() {
-		for op in code.bodies().iter().flat_map(|body| body.code().elements()) {
-			use parity_wasm::elements::Opcode::*;
-
-			macro_rules! match_eq {
-				($pattern:pat) => {
-					|val| if let $pattern = *val { true } else { false }
-				};
-			}
-
-			const DENIED: &[fn(&Opcode) -> bool] = &[
-				match_eq!(F32Load(_, _)),
-				match_eq!(F64Load(_, _)),
-				match_eq!(F32Store(_, _)),
-				match_eq!(F64Store(_, _)),
-				match_eq!(F32Const(_)),
-				match_eq!(F64Const(_)),
-				match_eq!(F32Eq),
-				match_eq!(F32Ne),
-				match_eq!(F32Lt),
-				match_eq!(F32Gt),
-				match_eq!(F32Le),
-				match_eq!(F32Ge),
-				match_eq!(F64Eq),
-				match_eq!(F64Ne),
-				match_eq!(F64Lt),
-				match_eq!(F64Gt),
-				match_eq!(F64Le),
-				match_eq!(F64Ge),
-				match_eq!(F32Abs),
-				match_eq!(F32Neg),
-				match_eq!(F32Ceil),
-				match_eq!(F32Floor),
-				match_eq!(F32Trunc),
-				match_eq!(F32Nearest),
-				match_eq!(F32Sqrt),
-				match_eq!(F32Add),
-				match_eq!(F32Sub),
-				match_eq!(F32Mul),
-				match_eq!(F32Div),
-				match_eq!(F32Min),
-				match_eq!(F32Max),
-				match_eq!(F32Copysign),
-				match_eq!(F64Abs),
-				match_eq!(F64Neg),
-				match_eq!(F64Ceil),
-				match_eq!(F64Floor),
-				match_eq!(F64Trunc),
-				match_eq!(F64Nearest),
-				match_eq!(F64Sqrt),
-				match_eq!(F64Add),
-				match_eq!(F64Sub),
-				match_eq!(F64Mul),
-				match_eq!(F64Div),
-				match_eq!(F64Min),
-				match_eq!(F64Max),
-				match_eq!(F64Copysign),
-				match_eq!(F32ConvertSI32),
-				match_eq!(F32ConvertUI32),
-				match_eq!(F32ConvertSI64),
-				match_eq!(F32ConvertUI64),
-				match_eq!(F32DemoteF64),
-				match_eq!(F64ConvertSI32),
-				match_eq!(F64ConvertUI32),
-				match_eq!(F64ConvertSI64),
-				match_eq!(F64ConvertUI64),
-				match_eq!(F64PromoteF32),
-				match_eq!(F32ReinterpretI32),
-				match_eq!(F64ReinterpretI64),
-				match_eq!(I32TruncSF32),
-				match_eq!(I32TruncUF32),
-				match_eq!(I32TruncSF64),
-				match_eq!(I32TruncUF64),
-				match_eq!(I64TruncSF32),
-				match_eq!(I64TruncUF32),
-				match_eq!(I64TruncSF64),
-				match_eq!(I64TruncUF64),
-				match_eq!(I32ReinterpretF32),
-				match_eq!(I64ReinterpretF64),
-			];
-
-			if DENIED.iter().any(|is_denied| is_denied(op)) {
-				return Err(Error(format!("Floating point operation denied: {:?}", op)));
-			}
-		}
-	}
-
-	if let (Some(sec), Some(types)) = (module.function_section(), module.type_section()) {
-		use parity_wasm::elements::{Type, ValueType};
-
-		let types = types.types();
-
-		for sig in sec.entries() {
-			if let Some(typ) = types.get(sig.type_ref() as usize) {
-				match *typ {
-					Type::Function(ref func) => {
-						if func.params()
-							.iter()
-							.chain(func.return_type().as_ref())
-							.any(|&typ| typ == ValueType::F32 || typ == ValueType::F64)
-						{
-							return Err(Error(format!("Use of floating point types denied")));
-						}
-					}
-				}
-			}
-		}
-	}
-
-	Ok(())
-}
-
-pub fn validate_module(module: Module) -> Result<ValidatedModule, Error> {
-	let mut context_builder = ModuleContextBuilder::new();
-	let mut imported_globals = Vec::new();
-	let mut labels = HashMap::new();
-
-	// Copy types from module as is.
-	context_builder.set_types(
-		module
-			.type_section()
-			.map(|ts| {
-				ts.types()
-					.into_iter()
-					.map(|&Type::Function(ref ty)| ty)
-					.cloned()
-					.collect()
-			})
-			.unwrap_or_default(),
-	);
-
-	// Fill elements with imported values.
-	for import_entry in module
-		.import_section()
-		.map(|i| i.entries())
-		.unwrap_or_default()
-	{
-		match *import_entry.external() {
-			External::Function(idx) => context_builder.push_func_type_index(idx),
-			External::Table(ref table) => context_builder.push_table(table.clone()),
-			External::Memory(ref memory) => context_builder.push_memory(memory.clone()),
-			External::Global(ref global) => {
-				context_builder.push_global(global.clone());
-				imported_globals.push(global.clone());
-			}
-		}
-	}
-
-	// Concatenate elements with defined in the module.
-	if let Some(function_section) = module.function_section() {
-		for func_entry in function_section.entries() {
-			context_builder.push_func_type_index(func_entry.type_ref())
-		}
-	}
-	if let Some(table_section) = module.table_section() {
-		for table_entry in table_section.entries() {
-			validate_table_type(table_entry)?;
-			context_builder.push_table(table_entry.clone());
-		}
-	}
-	if let Some(mem_section) = module.memory_section() {
-		for mem_entry in mem_section.entries() {
-			validate_memory_type(mem_entry)?;
-			context_builder.push_memory(mem_entry.clone());
-		}
-	}
-	if let Some(global_section) = module.global_section() {
-		for global_entry in global_section.entries() {
-			validate_global_entry(global_entry, &imported_globals)?;
-			context_builder.push_global(global_entry.global_type().clone());
-		}
-	}
-
-	let context = context_builder.build();
-
-	let function_section_len = module
-		.function_section()
-		.map(|s| s.entries().len())
-		.unwrap_or(0);
-	let code_section_len = module.code_section().map(|s| s.bodies().len()).unwrap_or(0);
-	if function_section_len != code_section_len {
-		return Err(Error(format!(
-			"length of function section is {}, while len of code section is {}",
-			function_section_len,
-			code_section_len
-		)));
-	}
-
-	// validate every function body in user modules
-	if function_section_len != 0 {
-		// tests use invalid code
-		let function_section = module.function_section().expect(
-			"function_section_len != 0; qed",
-		);
-		let code_section = module.code_section().expect(
-			"function_section_len != 0; function_section_len == code_section_len; qed",
-		);
-		// check every function body
-		for (index, function) in function_section.entries().iter().enumerate() {
-			let function_body = code_section.bodies().get(index as usize).ok_or(
-				Error(format!(
-					"Missing body for function {}",
-					index
-				)),
-			)?;
-			let func_labels = Validator::validate_function(&context, function, function_body)
-				.map_err(|e| {
-					let Error(ref msg) = e;
-					Error(format!("Function #{} validation error: {}", index, msg))
-				})?;
-			labels.insert(index, func_labels);
-		}
-	}
-
-	// validate start section
-	if let Some(start_fn_idx) = module.start_section() {
-		let (params, return_ty) = context.require_function(start_fn_idx)?;
-		if return_ty != BlockType::NoResult || params.len() != 0 {
-			return Err(Error(
-				"start function expected to have type [] -> []".into(),
-			));
-		}
-	}
-
-	// validate export section
-	if let Some(export_section) = module.export_section() {
-		let mut export_names = HashSet::with_capacity(export_section.entries().len());
-		for export in export_section.entries() {
-			// HashSet::insert returns false if item already in set.
-			let duplicate = export_names.insert(export.field()) == false;
-			if duplicate {
-				return Err(Error(
-					format!("duplicate export {}", export.field()),
-				));
-			}
-			match *export.internal() {
-				Internal::Function(function_index) => {
-					context.require_function(function_index)?;
-				}
-				Internal::Global(global_index) => {
-					context.require_global(global_index, Some(false))?;
-				}
-				Internal::Memory(memory_index) => {
-					context.require_memory(memory_index)?;
-				}
-				Internal::Table(table_index) => {
-					context.require_table(table_index)?;
-				}
-			}
-		}
-	}
-
-	// validate import section
-	if let Some(import_section) = module.import_section() {
-		for import in import_section.entries() {
-			match *import.external() {
-				External::Function(function_type_index) => {
-					context.require_function_type(function_type_index)?;
-				}
-				External::Global(ref global_type) => {
-					if global_type.is_mutable() {
-						return Err(Error(format!(
-							"trying to import mutable global {}",
-							import.field()
-						)));
-					}
-				}
-				External::Memory(ref memory_type) => {
-					validate_memory_type(memory_type)?;
-				}
-				External::Table(ref table_type) => {
-					validate_table_type(table_type)?;
-				}
-			}
-		}
-	}
-
-	// there must be no greater than 1 table in tables index space
-	if context.tables().len() > 1 {
-		return Err(Error(format!(
-			"too many tables in index space: {}",
-			context.tables().len()
-		)));
-	}
-
-	// there must be no greater than 1 linear memory in memory index space
-	if context.memories().len() > 1 {
-		return Err(Error(format!(
-			"too many memory regions in index space: {}",
-			context.memories().len()
-		)));
-	}
-
-	// use data section to initialize linear memory regions
-	if let Some(data_section) = module.data_section() {
-		for data_segment in data_section.entries() {
-			context.require_memory(data_segment.index())?;
-			let init_ty = expr_const_type(data_segment.offset(), context.globals())?;
-			if init_ty != ValueType::I32 {
-				return Err(Error("segment offset should return I32".into()));
-			}
-		}
-	}
-
-	// use element section to fill tables
-	if let Some(element_section) = module.elements_section() {
-		for element_segment in element_section.entries() {
-			context.require_table(element_segment.index())?;
-
-			let init_ty = expr_const_type(element_segment.offset(), context.globals())?;
-			if init_ty != ValueType::I32 {
-				return Err(Error("segment offset should return I32".into()));
-			}
-
-			for function_index in element_segment.members() {
-				context.require_function(*function_index)?;
-			}
-		}
-	}
-
-	Ok(ValidatedModule {
-		module,
-		labels
-	})
-}
-
-fn validate_limits(limits: &ResizableLimits) -> Result<(), Error> {
-	if let Some(maximum) = limits.maximum() {
-		if limits.initial() > maximum {
-			return Err(Error(format!(
-				"maximum limit {} is less than minimum {}",
-				maximum,
-				limits.initial()
-			)));
-		}
-	}
-	Ok(())
-}
-
-fn validate_memory_type(memory_type: &MemoryType) -> Result<(), Error> {
-	let initial: Pages = Pages(memory_type.limits().initial() as usize);
-	let maximum: Option<Pages> = memory_type.limits().maximum().map(|m| Pages(m as usize));
-	::memory::validate_memory(initial, maximum).map_err(Error)
-}
-
-fn validate_table_type(table_type: &TableType) -> Result<(), Error> {
-	validate_limits(table_type.limits())
-}
-
-fn validate_global_entry(global_entry: &GlobalEntry, globals: &[GlobalType]) -> Result<(), Error> {
-	let init = global_entry.init_expr();
-		let init_expr_ty = expr_const_type(init, globals)?;
-		if init_expr_ty != global_entry.global_type().content_type() {
-			return Err(Error(format!(
-				"Trying to initialize variable of type {:?} with value of type {:?}",
-				global_entry.global_type().content_type(),
-				init_expr_ty
-			)));
-		}
-		Ok(())
-}
-
-/// Returns type of this constant expression.
-fn expr_const_type(init_expr: &InitExpr, globals: &[GlobalType]) -> Result<ValueType, Error> {
-	let code = init_expr.code();
-	if code.len() != 2 {
-		return Err(Error(
-			"Init expression should always be with length 2".into(),
-		));
-	}
-	let expr_ty: ValueType = match code[0] {
-		Opcode::I32Const(_) => ValueType::I32,
-		Opcode::I64Const(_) => ValueType::I64,
-		Opcode::F32Const(_) => ValueType::F32,
-		Opcode::F64Const(_) => ValueType::F64,
-		Opcode::GetGlobal(idx) => {
-			match globals.get(idx as usize) {
-				Some(target_global) => {
-					if target_global.is_mutable() {
-						return Err(Error(format!("Global {} is mutable", idx)));
-					}
-					target_global.content_type()
-				}
-				None => {
-					return Err(Error(
-						format!("Global {} doesn't exists or not yet defined", idx),
-					))
-				}
-			}
-		}
-		_ => return Err(Error("Non constant opcode in init expr".into())),
-	};
-	if code[1] != Opcode::End {
-		return Err(Error("Expression doesn't ends with `end` opcode".into()));
-	}
-	Ok(expr_ty)
-}

src/validation/tests.rs

@@ -1,301 +0,0 @@
-use super::validate_module;
-use parity_wasm::builder::module;
-use parity_wasm::elements::{
-    External, GlobalEntry, GlobalType, ImportEntry, InitExpr, MemoryType,
-    Opcode, Opcodes, TableType, ValueType, BlockType
-};
-
-#[test]
-fn empty_is_valid() {
-	let module = module().build();
-	assert!(validate_module(module).is_ok());
-}
-
-#[test]
-fn limits() {
-	let test_cases = vec![
-		// min > max
-		(10, Some(9), false),
-		// min = max
-		(10, Some(10), true),
-		// table/memory is always valid without max
-		(10, None, true),
-	];
-
-	for (min, max, is_valid) in test_cases {
-		// defined table
-		let m = module()
-			.table()
-				.with_min(min)
-				.with_max(max)
-				.build()
-			.build();
-		assert_eq!(validate_module(m).is_ok(), is_valid);
-
-		// imported table
-		let m = module()
-			.with_import(
-				ImportEntry::new(
-					"core".into(),
-					"table".into(),
-					External::Table(TableType::new(min, max))
-				)
-			)
-			.build();
-		assert_eq!(validate_module(m).is_ok(), is_valid);
-
-		// defined memory
-		let m = module()
-			.memory()
-				.with_min(min)
-				.with_max(max)
-				.build()
-			.build();
-		assert_eq!(validate_module(m).is_ok(), is_valid);
-
-		// imported table
-		let m = module()
-			.with_import(
-				ImportEntry::new(
-					"core".into(),
-					"memory".into(),
-					External::Memory(MemoryType::new(min, max))
-				)
-			)
-			.build();
-		assert_eq!(validate_module(m).is_ok(), is_valid);
-	}
-}
-
-#[test]
-fn global_init_const() {
-	let m = module()
-		.with_global(
-			GlobalEntry::new(
-				GlobalType::new(ValueType::I32, true),
-				InitExpr::new(
-					vec![Opcode::I32Const(42), Opcode::End]
-				)
-			)
-		)
-		.build();
-	assert!(validate_module(m).is_ok());
-
-	// init expr type differs from declared global type
-	let m = module()
-		.with_global(
-			GlobalEntry::new(
-				GlobalType::new(ValueType::I64, true),
-				InitExpr::new(vec![Opcode::I32Const(42), Opcode::End])
-			)
-		)
-		.build();
-	assert!(validate_module(m).is_err());
-}
-
-#[test]
-fn global_init_global() {
-	let m = module()
-		.with_import(
-			ImportEntry::new(
-				"env".into(),
-				"ext_global".into(),
-				External::Global(GlobalType::new(ValueType::I32, false))
-			)
-		)
-		.with_global(
-			GlobalEntry::new(
-				GlobalType::new(ValueType::I32, true),
-				InitExpr::new(vec![Opcode::GetGlobal(0), Opcode::End])
-			)
-		)
-		.build();
-	assert!(validate_module(m).is_ok());
-
-	// get_global can reference only previously defined globals
-	let m = module()
-		.with_global(
-			GlobalEntry::new(
-				GlobalType::new(ValueType::I32, true),
-				InitExpr::new(vec![Opcode::GetGlobal(0), Opcode::End])
-			)
-		)
-		.build();
-	assert!(validate_module(m).is_err());
-
-	// get_global can reference only const globals
-	let m = module()
-		.with_import(
-			ImportEntry::new(
-				"env".into(),
-				"ext_global".into(),
-				External::Global(GlobalType::new(ValueType::I32, true))
-			)
-		)
-		.with_global(
-			GlobalEntry::new(
-				GlobalType::new(ValueType::I32, true),
-				InitExpr::new(vec![Opcode::GetGlobal(0), Opcode::End])
-			)
-		)
-		.build();
-	assert!(validate_module(m).is_err());
-
-	// get_global in init_expr can only refer to imported globals.
-	let m = module()
-		.with_global(
-			GlobalEntry::new(
-				GlobalType::new(ValueType::I32, false),
-				InitExpr::new(vec![Opcode::I32Const(0), Opcode::End])
-			)
-		)
-		.with_global(
-			GlobalEntry::new(
-				GlobalType::new(ValueType::I32, true),
-				InitExpr::new(vec![Opcode::GetGlobal(0), Opcode::End])
-			)
-		)
-		.build();
-	assert!(validate_module(m).is_err());
-}
-
-#[test]
-fn global_init_misc() {
-	// without delimiting End opcode
-	let m = module()
-		.with_global(
-			GlobalEntry::new(
-				GlobalType::new(ValueType::I32, true),
-				InitExpr::new(vec![Opcode::I32Const(42)])
-			)
-		)
-		.build();
-	assert!(validate_module(m).is_err());
-
-	// empty init expr
-	let m = module()
-		.with_global(
-			GlobalEntry::new(
-				GlobalType::new(ValueType::I32, true),
-				InitExpr::new(vec![Opcode::End])
-			)
-		)
-		.build();
-	assert!(validate_module(m).is_err());
-
-	// not an constant opcode used
-	let m = module()
-		.with_global(
-			GlobalEntry::new(
-				GlobalType::new(ValueType::I32, true),
-				InitExpr::new(vec![Opcode::Unreachable, Opcode::End])
-			)
-		)
-		.build();
-	assert!(validate_module(m).is_err());
-}
-
-#[test]
-fn module_limits_validity() {
-	// module cannot contain more than 1 memory atm.
-	let m = module()
-		.with_import(
-			ImportEntry::new(
-				"core".into(),
-				"memory".into(),
-				External::Memory(MemoryType::new(10, None))
-			)
-		)
-		.memory()
-			.with_min(10)
-			.build()
-		.build();
-	assert!(validate_module(m).is_err());
-
-	// module cannot contain more than 1 table atm.
-	let m = module()
-		.with_import(
-			ImportEntry::new(
-				"core".into(),
-				"table".into(),
-				External::Table(TableType::new(10, None))
-			)
-		)
-		.table()
-			.with_min(10)
-			.build()
-		.build();
-	assert!(validate_module(m).is_err());
-}
-
-#[test]
-fn funcs() {
-	// recursive function calls is legal.
-	let m = module()
-		.function()
-			.signature().return_type().i32().build()
-			.body().with_opcodes(Opcodes::new(vec![
-				Opcode::Call(1),
-				Opcode::End,
-			])).build()
-			.build()
-		.function()
-			.signature().return_type().i32().build()
-			.body().with_opcodes(Opcodes::new(vec![
-				Opcode::Call(0),
-				Opcode::End,
-			])).build()
-			.build()
-		.build();
-	assert!(validate_module(m).is_ok());
-}
-
-#[test]
-fn globals() {
-	// import immutable global is legal.
-	let m = module()
-		.with_import(
-			ImportEntry::new(
-				"env".into(),
-				"ext_global".into(),
-				External::Global(GlobalType::new(ValueType::I32, false))
-			)
-		)
-		.build();
-	assert!(validate_module(m).is_ok());
-
-	// import mutable global is invalid.
-	let m = module()
-		.with_import(
-			ImportEntry::new(
-				"env".into(),
-				"ext_global".into(),
-				External::Global(GlobalType::new(ValueType::I32, true))
-			)
-		)
-		.build();
-	assert!(validate_module(m).is_err());
-}
-
-#[test]
-fn if_else_with_return_type_validation() {
-	let m = module()
-		.function()
-			.signature().build()
-			.body().with_opcodes(Opcodes::new(vec![
-				Opcode::I32Const(1),
-				Opcode::If(BlockType::NoResult),
-					Opcode::I32Const(1),
-					Opcode::If(BlockType::Value(ValueType::I32)),
-						Opcode::I32Const(1),
-					Opcode::Else,
-						Opcode::I32Const(2),
-					Opcode::End,
-					Opcode::Drop,
-				Opcode::End,
-				Opcode::End,
-			])).build()
-			.build()
-		.build();
-	validate_module(m).unwrap();
-}

src/validation/util.rs

@@ -1,112 +0,0 @@
-use parity_wasm::elements::{Local, ValueType};
-use validation::Error;
-
-/// Locals are the concatenation of a slice of function parameters
-/// with function declared local variables.
-///
-/// Local variables are given in the form of groups represented by pairs
-/// of a value_type and a count.
-#[derive(Debug)]
-pub struct Locals<'a> {
-	params: &'a [ValueType],
-	local_groups: &'a [Local],
-}
-
-impl<'a> Locals<'a> {
-	pub fn new(params: &'a [ValueType], local_groups: &'a [Local]) -> Locals<'a> {
-		Locals {
-			params,
-			local_groups,
-		}
-	}
-
-	/// Returns the type of a local variable (either a declared local or a param).
-	///
-	/// Returns `Err` in the case of overflow or when idx falls out of range.
-	pub fn type_of_local(&self, idx: u32) -> Result<ValueType, Error> {
-		if let Some(param) = self.params.get(idx as usize) {
-			return Ok(*param);
-		}
-
-		// If an index doesn't point to a param, then we have to look into local declarations.
-		let mut start_idx = self.params.len() as u32;
-		for locals_group in self.local_groups {
-			let end_idx = start_idx
-				.checked_add(locals_group.count())
-				.ok_or_else(|| Error(String::from("Locals range not in 32-bit range")))?;
-
-			if idx >= start_idx && idx < end_idx {
-				return Ok(locals_group.value_type());
-			}
-
-			start_idx = end_idx;
-		}
-
-		// We didn't find anything, that's an error.
-		// At this moment `start_idx` should hold the count of all locals
-		// (since it's either set to the `end_idx` or equal to `params.len()`)
-		let total_count = start_idx;
-
-		Err(Error(format!(
-			"Trying to access local with index {} when there are only {} locals",
-			idx, total_count
-		)))
-	}
-}
-
-#[cfg(test)]
-mod tests {
-	use super::*;
-
-	#[test]
-	fn locals_it_works() {
-		let params = vec![ValueType::I32, ValueType::I64];
-		let local_groups = vec![Local::new(2, ValueType::F32), Local::new(2, ValueType::F64)];
-		let locals = Locals::new(&params, &local_groups);
-
-		assert_matches!(locals.type_of_local(0), Ok(ValueType::I32));
-		assert_matches!(locals.type_of_local(1), Ok(ValueType::I64));
-		assert_matches!(locals.type_of_local(2), Ok(ValueType::F32));
-		assert_matches!(locals.type_of_local(3), Ok(ValueType::F32));
-		assert_matches!(locals.type_of_local(4), Ok(ValueType::F64));
-		assert_matches!(locals.type_of_local(5), Ok(ValueType::F64));
-		assert_matches!(locals.type_of_local(6), Err(_));
-	}
-
-	#[test]
-	fn locals_no_declared_locals() {
-		let params = vec![ValueType::I32];
-		let locals = Locals::new(&params, &[]);
-
-		assert_matches!(locals.type_of_local(0), Ok(ValueType::I32));
-		assert_matches!(locals.type_of_local(1), Err(_));
-	}
-
-	#[test]
-	fn locals_no_params() {
-		let local_groups = vec![Local::new(2, ValueType::I32), Local::new(3, ValueType::I64)];
-		let locals = Locals::new(&[], &local_groups);
-
-		assert_matches!(locals.type_of_local(0), Ok(ValueType::I32));
-		assert_matches!(locals.type_of_local(1), Ok(ValueType::I32));
-		assert_matches!(locals.type_of_local(2), Ok(ValueType::I64));
-		assert_matches!(locals.type_of_local(3), Ok(ValueType::I64));
-		assert_matches!(locals.type_of_local(4), Ok(ValueType::I64));
-		assert_matches!(locals.type_of_local(5), Err(_));
-	}
-
-	#[test]
-	fn locals_u32_overflow() {
-		let local_groups = vec![
-			Local::new(u32::max_value(), ValueType::I32),
-			Local::new(1, ValueType::I64),
-		];
-		let locals = Locals::new(&[], &local_groups);
-
-		assert_matches!(
-			locals.type_of_local(u32::max_value() - 1),
-			Ok(ValueType::I32)
-		);
-		assert_matches!(locals.type_of_local(u32::max_value()), Err(_));
-	}
-}

test.sh

@@ -2,8 +2,18 @@
 
 set -eux
 
+EXTRA_ARGS=""
+
+if [ -n "${TARGET-}" ]; then
+    # Tests build in debug mode are prohibitively
+    # slow when ran under emulation so that
+    # e.g. Travis CI will hit timeouts.
+    EXTRA_ARGS="--release --target=${TARGET}"
+    export RUSTFLAGS="--cfg debug_assertions"
+fi
+
 cd $(dirname $0)
 
-time cargo test
+time cargo test --all ${EXTRA_ARGS}
 
 cd -

tests/spec/mod.rs

@@ -1,12 +1,12 @@
 mod run;
 
 macro_rules! run_test {
-    ($label: expr, $test_name: ident) => (
+    ($label: expr, $test_name: ident) => {
         #[test]
         fn $test_name() {
             self::run::spec($label)
         }
-    );
+    };
 }
 
 run_test!("address", wasm_address);
@@ -22,7 +22,9 @@ run_test!("call_indirect", wasm_call_indirect);
 run_test!("comments", wasm_comments);
 run_test!("const", wasm_const);
 run_test!("conversions", wasm_conversions);
+run_test!("custom", wasm_custom);
 run_test!("custom_section", wasm_custom_section);
+run_test!("data", wasm_data);
 run_test!("elem", wasm_elem);
 run_test!("endianness", wasm_endianness);
 run_test!("exports", wasm_exports);

tests/spec/run.rs

@@ -1,21 +1,25 @@
 #![cfg(test)]
 
 use std::collections::HashMap;
+use std::fs::File;
 
 use wabt::script::{self, Action, Command, CommandKind, ScriptParser, Value};
 use wasmi::memory_units::Pages;
-use wasmi::{Error as InterpreterError, Externals, FuncInstance, FuncRef, GlobalDescriptor,
-            GlobalInstance, GlobalRef, ImportResolver, ImportsBuilder, MemoryDescriptor,
-            MemoryInstance, MemoryRef, Module, ModuleImportResolver, ModuleInstance, ModuleRef,
-            RuntimeArgs, RuntimeValue, Signature, TableDescriptor, TableInstance, TableRef, Trap};
+use wasmi::{
+    Error as InterpreterError, Externals, FuncInstance, FuncRef, GlobalDescriptor, GlobalInstance,
+    GlobalRef, ImportResolver, ImportsBuilder, MemoryDescriptor, MemoryInstance, MemoryRef, Module,
+    ModuleImportResolver, ModuleInstance, ModuleRef, RuntimeArgs, RuntimeValue, Signature,
+    TableDescriptor, TableInstance, TableRef, Trap,
+};
 
 fn spec_to_runtime_value(val: Value<u32, u64>) -> RuntimeValue {
-	match val {
-		Value::I32(v) => RuntimeValue::I32(v),
-		Value::I64(v) => RuntimeValue::I64(v),
-		Value::F32(v) => RuntimeValue::F32(v.into()),
-		Value::F64(v) => RuntimeValue::F64(v.into()),
-	}
+    match val {
+        Value::I32(v) => RuntimeValue::I32(v),
+        Value::I64(v) => RuntimeValue::I64(v),
+        Value::F32(v) => RuntimeValue::F32(v.into()),
+        Value::F64(v) => RuntimeValue::F64(v.into()),
+        Value::V128(_) => panic!("v128 is not supported"),
+    }
 }
 
 #[derive(Debug)]
@@ -47,15 +51,15 @@ struct SpecModule {
 }
 
 impl SpecModule {
-	fn new() -> Self {
-		SpecModule {
-			table: TableInstance::alloc(10, Some(20)).unwrap(),
-			memory: MemoryInstance::alloc(Pages(1), Some(Pages(2))).unwrap(),
-			global_i32: GlobalInstance::alloc(RuntimeValue::I32(666), false),
-			global_f32: GlobalInstance::alloc(RuntimeValue::F32(666.0.into()), false),
-			global_f64: GlobalInstance::alloc(RuntimeValue::F64(666.0.into()), false),
-		}
-	}
+    fn new() -> Self {
+        SpecModule {
+            table: TableInstance::alloc(10, Some(20)).unwrap(),
+            memory: MemoryInstance::alloc(Pages(1), Some(Pages(2))).unwrap(),
+            global_i32: GlobalInstance::alloc(RuntimeValue::I32(666), false),
+            global_f32: GlobalInstance::alloc(RuntimeValue::F32(666.0.into()), false),
+            global_f64: GlobalInstance::alloc(RuntimeValue::F64(666.0.into()), false),
+        }
+    }
 }
 
 const PRINT_FUNC_INDEX: usize = 0;
@@ -82,29 +86,29 @@ impl ModuleImportResolver for SpecModule {
         field_name: &str,
         func_type: &Signature,
     ) -> Result<FuncRef, InterpreterError> {
-		let index = match field_name {
-			"print" => PRINT_FUNC_INDEX,
-			"print_i32" => PRINT_FUNC_INDEX,
-			"print_i32_f32" => PRINT_FUNC_INDEX,
-			"print_f64_f64" => PRINT_FUNC_INDEX,
-			"print_f32" => PRINT_FUNC_INDEX,
-			"print_f64" => PRINT_FUNC_INDEX,
-			_ => {
-				return Err(InterpreterError::Instantiation(format!(
-					"Unknown host func import {}",
-					field_name
-				)));
-			}
-		};
+        let index = match field_name {
+            "print" => PRINT_FUNC_INDEX,
+            "print_i32" => PRINT_FUNC_INDEX,
+            "print_i32_f32" => PRINT_FUNC_INDEX,
+            "print_f64_f64" => PRINT_FUNC_INDEX,
+            "print_f32" => PRINT_FUNC_INDEX,
+            "print_f64" => PRINT_FUNC_INDEX,
+            _ => {
+                return Err(InterpreterError::Instantiation(format!(
+                    "Unknown host func import {}",
+                    field_name
+                )));
+            }
+        };
 
-		if func_type.return_type().is_some() {
-			return Err(InterpreterError::Instantiation(
-				"Function `print_` have unit return type".into(),
-			));
-		}
+        if func_type.return_type().is_some() {
+            return Err(InterpreterError::Instantiation(
+                "Function `print_` have unit return type".into(),
+            ));
+        }
 
         let func = FuncInstance::alloc_host(func_type.clone(), index);
-		return Ok(func);
+        return Ok(func);
     }
 
     fn resolve_global(
@@ -112,372 +116,389 @@ impl ModuleImportResolver for SpecModule {
         field_name: &str,
         _global_type: &GlobalDescriptor,
     ) -> Result<GlobalRef, InterpreterError> {
-		match field_name {
-			"global_i32" => Ok(self.global_i32.clone()),
-			"global_f32" => Ok(self.global_f32.clone()),
-			"global_f64" => Ok(self.global_f64.clone()),
-			_ => Err(InterpreterError::Instantiation(format!(
-				"Unknown host global import {}",
-				field_name
-			))),
-		}
-	}
+        match field_name {
+            "global_i32" => Ok(self.global_i32.clone()),
+            "global_f32" => Ok(self.global_f32.clone()),
+            "global_f64" => Ok(self.global_f64.clone()),
+            _ => Err(InterpreterError::Instantiation(format!(
+                "Unknown host global import {}",
+                field_name
+            ))),
+        }
+    }
 
-	fn resolve_memory(
-		&self,
-		field_name: &str,
-		_memory_type: &MemoryDescriptor,
-	) -> Result<MemoryRef, InterpreterError> {
-		if field_name == "memory" {
-			return Ok(self.memory.clone());
-		}
+    fn resolve_memory(
+        &self,
+        field_name: &str,
+        _memory_type: &MemoryDescriptor,
+    ) -> Result<MemoryRef, InterpreterError> {
+        if field_name == "memory" {
+            return Ok(self.memory.clone());
+        }
 
-		Err(InterpreterError::Instantiation(format!(
-			"Unknown host memory import {}",
-			field_name
-		)))
-	}
+        Err(InterpreterError::Instantiation(format!(
+            "Unknown host memory import {}",
+            field_name
+        )))
+    }
 
-	fn resolve_table(
-		&self,
-		field_name: &str,
-		_table_type: &TableDescriptor,
-	) -> Result<TableRef, InterpreterError> {
-		if field_name == "table" {
-			return Ok(self.table.clone());
-		}
+    fn resolve_table(
+        &self,
+        field_name: &str,
+        _table_type: &TableDescriptor,
+    ) -> Result<TableRef, InterpreterError> {
+        if field_name == "table" {
+            return Ok(self.table.clone());
+        }
 
-		Err(InterpreterError::Instantiation(format!(
-			"Unknown host table import {}",
-			field_name
-		)))
-	}
+        Err(InterpreterError::Instantiation(format!(
+            "Unknown host table import {}",
+            field_name
+        )))
+    }
 }
 
 struct SpecDriver {
-	spec_module: SpecModule,
-	instances: HashMap<String, ModuleRef>,
-	last_module: Option<ModuleRef>,
+    spec_module: SpecModule,
+    instances: HashMap<String, ModuleRef>,
+    last_module: Option<ModuleRef>,
 }
 
 impl SpecDriver {
-	fn new() -> SpecDriver {
-		SpecDriver {
-			spec_module: SpecModule::new(),
-			instances: HashMap::new(),
-			last_module: None,
-		}
-	}
+    fn new() -> SpecDriver {
+        SpecDriver {
+            spec_module: SpecModule::new(),
+            instances: HashMap::new(),
+            last_module: None,
+        }
+    }
 
-	fn spec_module(&mut self) -> &mut SpecModule {
-		&mut self.spec_module
-	}
+    fn spec_module(&mut self) -> &mut SpecModule {
+        &mut self.spec_module
+    }
 
-	fn add_module(&mut self, name: Option<String>, module: ModuleRef) {
-		self.last_module = Some(module.clone());
-		if let Some(name) = name {
-			self.instances.insert(name, module);
-		}
-	}
+    fn add_module(&mut self, name: Option<String>, module: ModuleRef) {
+        self.last_module = Some(module.clone());
+        if let Some(name) = name {
+            self.instances.insert(name, module);
+        }
+    }
 
-	fn module(&self, name: &str) -> Result<ModuleRef, InterpreterError> {
-		self.instances.get(name).cloned().ok_or_else(|| {
-			InterpreterError::Instantiation(format!("Module not registered {}", name))
-		})
-	}
+    fn module(&self, name: &str) -> Result<ModuleRef, InterpreterError> {
+        self.instances.get(name).cloned().ok_or_else(|| {
+            InterpreterError::Instantiation(format!("Module not registered {}", name))
+        })
+    }
 
-	fn module_or_last(&self, name: Option<&str>) -> Result<ModuleRef, InterpreterError> {
-		match name {
-			Some(name) => self.module(name),
-			None => self.last_module
-				.clone()
-				.ok_or_else(|| InterpreterError::Instantiation("No modules registered".into())),
-		}
-	}
+    fn module_or_last(&self, name: Option<&str>) -> Result<ModuleRef, InterpreterError> {
+        match name {
+            Some(name) => self.module(name),
+            None => self
+                .last_module
+                .clone()
+                .ok_or_else(|| InterpreterError::Instantiation("No modules registered".into())),
+        }
+    }
 }
 
 impl ImportResolver for SpecDriver {
-	fn resolve_func(
-		&self,
-		module_name: &str,
-		field_name: &str,
-		func_type: &Signature,
-	) -> Result<FuncRef, InterpreterError> {
-		if module_name == "spectest" {
-			self.spec_module.resolve_func(field_name, func_type)
-		} else {
-			self.module(module_name)?
-				.resolve_func(field_name, func_type)
-		}
-	}
+    fn resolve_func(
+        &self,
+        module_name: &str,
+        field_name: &str,
+        func_type: &Signature,
+    ) -> Result<FuncRef, InterpreterError> {
+        if module_name == "spectest" {
+            self.spec_module.resolve_func(field_name, func_type)
+        } else {
+            self.module(module_name)?
+                .resolve_func(field_name, func_type)
+        }
+    }
 
-	fn resolve_global(
-		&self,
-		module_name: &str,
-		field_name: &str,
-		global_type: &GlobalDescriptor,
-	) -> Result<GlobalRef, InterpreterError> {
-		if module_name == "spectest" {
-			self.spec_module.resolve_global(field_name, global_type)
-		} else {
-			self.module(module_name)?
-				.resolve_global(field_name, global_type)
-		}
-	}
+    fn resolve_global(
+        &self,
+        module_name: &str,
+        field_name: &str,
+        global_type: &GlobalDescriptor,
+    ) -> Result<GlobalRef, InterpreterError> {
+        if module_name == "spectest" {
+            self.spec_module.resolve_global(field_name, global_type)
+        } else {
+            self.module(module_name)?
+                .resolve_global(field_name, global_type)
+        }
+    }
 
-	fn resolve_memory(
-		&self,
-		module_name: &str,
-		field_name: &str,
-		memory_type: &MemoryDescriptor,
-	) -> Result<MemoryRef, InterpreterError> {
-		if module_name == "spectest" {
-			self.spec_module.resolve_memory(field_name, memory_type)
-		} else {
-			self.module(module_name)?
-				.resolve_memory(field_name, memory_type)
-		}
-	}
+    fn resolve_memory(
+        &self,
+        module_name: &str,
+        field_name: &str,
+        memory_type: &MemoryDescriptor,
+    ) -> Result<MemoryRef, InterpreterError> {
+        if module_name == "spectest" {
+            self.spec_module.resolve_memory(field_name, memory_type)
+        } else {
+            self.module(module_name)?
+                .resolve_memory(field_name, memory_type)
+        }
+    }
 
-	fn resolve_table(
-		&self,
-		module_name: &str,
-		field_name: &str,
-		table_type: &TableDescriptor,
-	) -> Result<TableRef, InterpreterError> {
-		if module_name == "spectest" {
-			self.spec_module.resolve_table(field_name, table_type)
-		} else {
-			self.module(module_name)?
-				.resolve_table(field_name, table_type)
-		}
-	}
+    fn resolve_table(
+        &self,
+        module_name: &str,
+        field_name: &str,
+        table_type: &TableDescriptor,
+    ) -> Result<TableRef, InterpreterError> {
+        if module_name == "spectest" {
+            self.spec_module.resolve_table(field_name, table_type)
+        } else {
+            self.module(module_name)?
+                .resolve_table(field_name, table_type)
+        }
+    }
 }
 
 fn try_load_module(wasm: &[u8]) -> Result<Module, Error> {
-	Module::from_buffer(wasm).map_err(|e| Error::Load(e.to_string()))
+    Module::from_buffer(wasm).map_err(|e| Error::Load(e.to_string()))
 }
 
 fn try_load(wasm: &[u8], spec_driver: &mut SpecDriver) -> Result<(), Error> {
-	let module = try_load_module(wasm)?;
-	let instance = ModuleInstance::new(&module, &ImportsBuilder::default())?;
-	instance
-		.run_start(spec_driver.spec_module())
-		.map_err(|trap| Error::Start(trap))?;
-	Ok(())
+    let module = try_load_module(wasm)?;
+    let instance = ModuleInstance::new(&module, &ImportsBuilder::default())?;
+    instance
+        .run_start(spec_driver.spec_module())
+        .map_err(|trap| Error::Start(trap))?;
+    Ok(())
 }
 
 fn load_module(
-	wasm: &[u8],
-	name: &Option<String>,
-	spec_driver: &mut SpecDriver,
+    wasm: &[u8],
+    name: &Option<String>,
+    spec_driver: &mut SpecDriver,
 ) -> Result<ModuleRef, Error> {
-	let module = try_load_module(wasm)?;
-	let instance = ModuleInstance::new(&module, spec_driver)
-		.map_err(|e| Error::Load(e.to_string()))?
-		.run_start(spec_driver.spec_module())
-		.map_err(|trap| Error::Start(trap))?;
+    let module = try_load_module(wasm)?;
+    let instance = ModuleInstance::new(&module, spec_driver)
+        .map_err(|e| Error::Load(e.to_string()))?
+        .run_start(spec_driver.spec_module())
+        .map_err(|trap| Error::Start(trap))?;
 
-	let module_name = name.clone();
-	spec_driver.add_module(module_name, instance.clone());
+    let module_name = name.clone();
+    spec_driver.add_module(module_name, instance.clone());
 
-	Ok(instance)
+    Ok(instance)
 }
 
 fn run_action(
-	program: &mut SpecDriver,
-	action: &Action<u32, u64>,
+    program: &mut SpecDriver,
+    action: &Action<u32, u64>,
 ) -> Result<Option<RuntimeValue>, InterpreterError> {
-	match *action {
-		Action::Invoke {
-			ref module,
-			ref field,
-			ref args,
-		} => {
-			let module = program
-				.module_or_last(module.as_ref().map(|x| x.as_ref()))
-				.expect(&format!(
-					"Expected program to have loaded module {:?}",
-					module
-				));
-			let vec_args = args.iter()
-				.cloned()
-				.map(spec_to_runtime_value)
-				.collect::<Vec<_>>();
-			module.invoke_export(field, &vec_args, program.spec_module())
-		}
-		Action::Get {
-			ref module,
-			ref field,
-			..
-		} => {
-			let module = program
-				.module_or_last(module.as_ref().map(|x| x.as_ref()))
-				.expect(&format!(
-					"Expected program to have loaded module {:?}",
-					module
-				));
-			let global = module
-				.export_by_name(&field)
-				.ok_or_else(|| {
-					InterpreterError::Global(format!("Expected to have export with name {}", field))
-				})?
-				.as_global()
-				.cloned()
-				.ok_or_else(|| {
-					InterpreterError::Global(format!("Expected export {} to be a global", field))
-				})?;
-			Ok(Some(global.get()))
-		}
-	}
+    match *action {
+        Action::Invoke {
+            ref module,
+            ref field,
+            ref args,
+        } => {
+            let module = program
+                .module_or_last(module.as_ref().map(|x| x.as_ref()))
+                .expect(&format!(
+                    "Expected program to have loaded module {:?}",
+                    module
+                ));
+            let vec_args = args
+                .iter()
+                .cloned()
+                .map(spec_to_runtime_value)
+                .collect::<Vec<_>>();
+            module.invoke_export(field, &vec_args, program.spec_module())
+        }
+        Action::Get {
+            ref module,
+            ref field,
+            ..
+        } => {
+            let module = program
+                .module_or_last(module.as_ref().map(|x| x.as_ref()))
+                .expect(&format!(
+                    "Expected program to have loaded module {:?}",
+                    module
+                ));
+            let global = module
+                .export_by_name(&field)
+                .ok_or_else(|| {
+                    InterpreterError::Global(format!("Expected to have export with name {}", field))
+                })?
+                .as_global()
+                .cloned()
+                .ok_or_else(|| {
+                    InterpreterError::Global(format!("Expected export {} to be a global", field))
+                })?;
+            Ok(Some(global.get()))
+        }
+    }
 }
 
 pub fn spec(name: &str) {
-	println!("running test: {}", name);
-	try_spec(name).expect("Failed to run spec");
+    println!("running test: {}", name);
+    try_spec(name).expect("Failed to run spec");
 }
 
 fn try_spec(name: &str) -> Result<(), Error> {
-	let mut spec_driver = SpecDriver::new();
-	let spec_script_path = format!("tests/spec/testsuite/{}.wast", name);
-	let mut parser = ScriptParser::from_file(spec_script_path).expect("Can't read spec script");
-	let mut errors = vec![];
+    let mut spec_driver = SpecDriver::new();
+    let spec_script_path = format!("tests/spec/testsuite/{}.wast", name);
 
-	while let Some(Command { kind, line }) = parser.next()? {
-		macro_rules! assert_eq {
-			($a:expr, $b:expr) => {{
-				let (a, b) = ($a, $b);
+    use std::io::Read;
+    let mut spec_source = Vec::new();
+    let mut spec_file = File::open(&spec_script_path).expect("Can't open file");
+    spec_file
+        .read_to_end(&mut spec_source)
+        .expect("Can't read file");
 
-				if a != b {
-					errors.push(format!(
-						r#"ERROR (line {}):
+    let mut parser = ScriptParser::from_source_and_name(&spec_source, &format!("{}.wast", name))
+        .expect("Can't read spec script");
+    let mut errors = vec![];
+
+    while let Some(Command { kind, line }) = parser.next()? {
+        macro_rules! assert_eq {
+            ($a:expr, $b:expr) => {{
+                let (a, b) = ($a, $b);
+
+                if a != b {
+                    errors.push(format!(
+                        r#"ERROR (line {}):
   expected: {:?}
   got:      {:?}
 "#,
-						line, b, a,
-					));
-					}
-				}};
-		}
+                        line, b, a,
+                    ));
+                }
+            }};
+        }
 
-		match kind {
-			CommandKind::Module { name, module, .. } => {
-				load_module(&module.into_vec()?, &name, &mut spec_driver)
-					.expect("Failed to load module");
-			}
-			CommandKind::AssertReturn { action, expected } => {
-				let result = run_action(&mut spec_driver, &action);
-				match result {
-					Ok(result) => {
-						let spec_expected = expected
-							.iter()
-							.cloned()
-							.map(spec_to_runtime_value)
-							.collect::<Vec<_>>();
-						let actual_result = result.into_iter().collect::<Vec<RuntimeValue>>();
-						for (actual_result, spec_expected) in
-							actual_result.iter().zip(spec_expected.iter())
-						{
-							assert_eq!(actual_result.value_type(), spec_expected.value_type());
-							// f32::NAN != f32::NAN
-							match spec_expected {
-								&RuntimeValue::F32(val) if val.is_nan() => match actual_result {
-									&RuntimeValue::F32(val) => assert!(val.is_nan()),
-									_ => unreachable!(), // checked above that types are same
-								},
-								&RuntimeValue::F64(val) if val.is_nan() => match actual_result {
-									&RuntimeValue::F64(val) => assert!(val.is_nan()),
-									_ => unreachable!(), // checked above that types are same
-								},
-								spec_expected @ _ => assert_eq!(actual_result, spec_expected),
-							}
-						}
-					}
-					Err(e) => {
-						panic!("Expected action to return value, got error: {:?}", e);
-					}
-				}
-			}
-			CommandKind::AssertReturnCanonicalNan { action }
-			| CommandKind::AssertReturnArithmeticNan { action } => {
-				let result = run_action(&mut spec_driver, &action);
-				match result {
-					Ok(result) => {
-						for actual_result in result.into_iter().collect::<Vec<RuntimeValue>>() {
-							match actual_result {
-								RuntimeValue::F32(val) => if !val.is_nan() {
-									panic!("Expected nan value, got {:?}", val)
-								},
-								RuntimeValue::F64(val) => if !val.is_nan() {
-									panic!("Expected nan value, got {:?}", val)
-								},
-								val @ _ => {
-									panic!("Expected action to return float value, got {:?}", val)
-								}
-							}
-						}
-					}
-					Err(e) => {
-						panic!("Expected action to return value, got error: {:?}", e);
-					}
-				}
-			}
-			CommandKind::AssertExhaustion { action, .. } => {
-				let result = run_action(&mut spec_driver, &action);
-				match result {
-					Ok(result) => panic!("Expected exhaustion, got result: {:?}", result),
-					Err(_e) => {},
-				}
-			}
-			CommandKind::AssertTrap { action, .. } => {
-				let result = run_action(&mut spec_driver, &action);
-				match result {
-					Ok(result) => {
-						panic!(
-							"Expected action to result in a trap, got result: {:?}",
-							result
-						);
-					}
-					Err(_e) => {}
-				}
-			}
-			CommandKind::AssertInvalid { module, .. }
-			| CommandKind::AssertMalformed { module, .. }
-			| CommandKind::AssertUnlinkable { module, .. } => {
-				let module_load = try_load(&module.into_vec()?, &mut spec_driver);
-				match module_load {
-					Ok(_) => panic!("Expected invalid module definition, got some module!"),
-					Err(_e) => {},
-				}
-			}
-			CommandKind::AssertUninstantiable { module, .. } => {
-				match try_load(&module.into_vec()?, &mut spec_driver) {
-					Ok(_) => panic!("Expected error running start function at line {}", line),
-					Err(_e) => {},
-				}
-			}
-			CommandKind::Register { name, as_name, .. } => {
-				let module = match spec_driver.module_or_last(name.as_ref().map(|x| x.as_ref())) {
-					Ok(module) => module,
-					Err(e) => panic!("No such module, at line {} - ({:?})", e, line),
-				};
-				spec_driver.add_module(Some(as_name.clone()), module);
-			}
-			CommandKind::PerformAction(action) => match run_action(&mut spec_driver, &action) {
-				Ok(_) => {}
-				Err(e) => panic!("Failed to invoke action at line {}: {:?}", line, e),
-			},
-		}
-	}
+        println!("Running spec cmd {}: {:?}", line, kind);
 
-	if !errors.is_empty() {
-		use std::fmt::Write;
-		let mut out = "\n".to_owned();
-		for err in errors {
-			write!(out, "{}", err).expect("Error formatting errors");
-		}
-		panic!(out);
-	}
+        match kind {
+            CommandKind::Module { name, module, .. } => {
+                load_module(&module.into_vec(), &name, &mut spec_driver)
+                    .expect("Failed to load module");
+            }
+            CommandKind::AssertReturn { action, expected } => {
+                let result = run_action(&mut spec_driver, &action);
+                match result {
+                    Ok(result) => {
+                        let spec_expected = expected
+                            .iter()
+                            .cloned()
+                            .map(spec_to_runtime_value)
+                            .collect::<Vec<_>>();
+                        let actual_result = result.into_iter().collect::<Vec<RuntimeValue>>();
+                        for (actual_result, spec_expected) in
+                            actual_result.iter().zip(spec_expected.iter())
+                        {
+                            assert_eq!(actual_result.value_type(), spec_expected.value_type());
+                            // f32::NAN != f32::NAN
+                            match spec_expected {
+                                &RuntimeValue::F32(val) if val.is_nan() => match actual_result {
+                                    &RuntimeValue::F32(val) => assert!(val.is_nan()),
+                                    _ => unreachable!(), // checked above that types are same
+                                },
+                                &RuntimeValue::F64(val) if val.is_nan() => match actual_result {
+                                    &RuntimeValue::F64(val) => assert!(val.is_nan()),
+                                    _ => unreachable!(), // checked above that types are same
+                                },
+                                spec_expected @ _ => assert_eq!(actual_result, spec_expected),
+                            }
+                        }
+                    }
+                    Err(e) => {
+                        panic!("Expected action to return value, got error: {:?}", e);
+                    }
+                }
+            }
+            CommandKind::AssertReturnCanonicalNan { action }
+            | CommandKind::AssertReturnArithmeticNan { action } => {
+                let result = run_action(&mut spec_driver, &action);
+                match result {
+                    Ok(result) => {
+                        for actual_result in result.into_iter().collect::<Vec<RuntimeValue>>() {
+                            match actual_result {
+                                RuntimeValue::F32(val) => {
+                                    if !val.is_nan() {
+                                        panic!("Expected nan value, got {:?}", val)
+                                    }
+                                }
+                                RuntimeValue::F64(val) => {
+                                    if !val.is_nan() {
+                                        panic!("Expected nan value, got {:?}", val)
+                                    }
+                                }
+                                val @ _ => {
+                                    panic!("Expected action to return float value, got {:?}", val)
+                                }
+                            }
+                        }
+                    }
+                    Err(e) => {
+                        panic!("Expected action to return value, got error: {:?}", e);
+                    }
+                }
+            }
+            CommandKind::AssertExhaustion { action, .. } => {
+                let result = run_action(&mut spec_driver, &action);
+                match result {
+                    Ok(result) => panic!("Expected exhaustion, got result: {:?}", result),
+                    Err(_e) => {}
+                }
+            }
+            CommandKind::AssertTrap { action, .. } => {
+                let result = run_action(&mut spec_driver, &action);
+                match result {
+                    Ok(result) => {
+                        panic!(
+                            "Expected action to result in a trap, got result: {:?}",
+                            result
+                        );
+                    }
+                    Err(_e) => {}
+                }
+            }
+            CommandKind::AssertInvalid { module, .. }
+            | CommandKind::AssertMalformed { module, .. }
+            | CommandKind::AssertUnlinkable { module, .. } => {
+                let module_load = try_load(&module.into_vec(), &mut spec_driver);
+                match module_load {
+                    Ok(_) => panic!("Expected invalid module definition, got some module!"),
+                    Err(_e) => {}
+                }
+            }
+            CommandKind::AssertUninstantiable { module, .. } => {
+                match try_load(&module.into_vec(), &mut spec_driver) {
+                    Ok(_) => panic!("Expected error running start function at line {}", line),
+                    Err(_e) => {}
+                }
+            }
+            CommandKind::Register { name, as_name, .. } => {
+                let module = match spec_driver.module_or_last(name.as_ref().map(|x| x.as_ref())) {
+                    Ok(module) => module,
+                    Err(e) => panic!("No such module, at line {} - ({:?})", e, line),
+                };
+                spec_driver.add_module(Some(as_name.clone()), module);
+            }
+            CommandKind::PerformAction(action) => match run_action(&mut spec_driver, &action) {
+                Ok(_) => {}
+                Err(e) => panic!("Failed to invoke action at line {}: {:?}", line, e),
+            },
+        }
+    }
 
-	Ok(())
+    if !errors.is_empty() {
+        use std::fmt::Write;
+        let mut out = "\n".to_owned();
+        for err in errors {
+            write!(out, "{}", err).expect("Error formatting errors");
+        }
+        panic!(out);
+    }
+
+    Ok(())
 }

tests/spec/testsuite

@@ -1 +1 @@
-Subproject commit c538faa43217146f458b9bc2d4b704d0a4d80963
+Subproject commit c6a690f89a0dda3c79700aa6377d8b5d8a970eba

tests/spec_shim.rs

@@ -1,6 +1,6 @@
 //! Official spec testsuite.
 
-extern crate wasmi;
 extern crate wabt;
+extern crate wasmi;
 
 mod spec;

validation/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "wasmi-validation"
+version = "0.2.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2018"
+license = "MIT/Apache-2.0"
+repository = "https://github.com/paritytech/wasmi"
+description = "Wasm code validator"
+
+[dependencies]
+parity-wasm = { version = "0.40.1", default-features = false }
+
+[dev-dependencies]
+assert_matches = "1.1"
+
+[features]
+default = ["std"]
+std = ["parity-wasm/std"]
+core = []

validation/src/context.rs

@@ -0,0 +1,141 @@
+use crate::Error;
+use alloc::vec::Vec;
+use parity_wasm::elements::{
+    BlockType, FunctionType, GlobalType, MemoryType, TableType, ValueType,
+};
+
+#[derive(Default, Debug)]
+pub struct ModuleContext {
+    pub memories: Vec<MemoryType>,
+    pub tables: Vec<TableType>,
+    pub globals: Vec<GlobalType>,
+    pub types: Vec<FunctionType>,
+    pub func_type_indexes: Vec<u32>,
+}
+
+impl ModuleContext {
+    pub fn memories(&self) -> &[MemoryType] {
+        &self.memories
+    }
+
+    pub fn tables(&self) -> &[TableType] {
+        &self.tables
+    }
+
+    pub fn globals(&self) -> &[GlobalType] {
+        &self.globals
+    }
+
+    pub fn types(&self) -> &[FunctionType] {
+        &self.types
+    }
+
+    pub fn func_type_indexes(&self) -> &[u32] {
+        &self.func_type_indexes
+    }
+
+    pub fn require_memory(&self, idx: u32) -> Result<(), Error> {
+        if self.memories().get(idx as usize).is_none() {
+            return Err(Error(format!("Memory at index {} doesn't exists", idx)));
+        }
+        Ok(())
+    }
+
+    pub fn require_table(&self, idx: u32) -> Result<&TableType, Error> {
+        self.tables()
+            .get(idx as usize)
+            .ok_or_else(|| Error(format!("Table at index {} doesn't exists", idx)))
+    }
+
+    pub fn require_function(&self, idx: u32) -> Result<(&[ValueType], BlockType), Error> {
+        let ty_idx = self
+            .func_type_indexes()
+            .get(idx as usize)
+            .ok_or_else(|| Error(format!("Function at index {} doesn't exists", idx)))?;
+        self.require_function_type(*ty_idx)
+    }
+
+    pub fn require_function_type(&self, idx: u32) -> Result<(&[ValueType], BlockType), Error> {
+        let ty = self
+            .types()
+            .get(idx as usize)
+            .ok_or_else(|| Error(format!("Type at index {} doesn't exists", idx)))?;
+
+        let params = ty.params();
+        let return_ty = ty
+            .return_type()
+            .map(BlockType::Value)
+            .unwrap_or(BlockType::NoResult);
+        Ok((params, return_ty))
+    }
+
+    pub fn require_global(&self, idx: u32, mutability: Option<bool>) -> Result<&GlobalType, Error> {
+        let global = self
+            .globals()
+            .get(idx as usize)
+            .ok_or_else(|| Error(format!("Global at index {} doesn't exists", idx)))?;
+
+        if let Some(expected_mutable) = mutability {
+            if expected_mutable && !global.is_mutable() {
+                return Err(Error(format!("Expected global {} to be mutable", idx)));
+            }
+            if !expected_mutable && global.is_mutable() {
+                return Err(Error(format!("Expected global {} to be immutable", idx)));
+            }
+        }
+        Ok(global)
+    }
+}
+
+#[derive(Default)]
+pub struct ModuleContextBuilder {
+    memories: Vec<MemoryType>,
+    tables: Vec<TableType>,
+    globals: Vec<GlobalType>,
+    types: Vec<FunctionType>,
+    func_type_indexes: Vec<u32>,
+}
+
+impl ModuleContextBuilder {
+    pub fn new() -> ModuleContextBuilder {
+        ModuleContextBuilder::default()
+    }
+
+    pub fn push_memory(&mut self, memory: MemoryType) {
+        self.memories.push(memory);
+    }
+
+    pub fn push_table(&mut self, table: TableType) {
+        self.tables.push(table);
+    }
+
+    pub fn push_global(&mut self, global: GlobalType) {
+        self.globals.push(global);
+    }
+
+    pub fn set_types(&mut self, types: Vec<FunctionType>) {
+        self.types = types;
+    }
+
+    pub fn push_func_type_index(&mut self, func_type_index: u32) {
+        self.func_type_indexes.push(func_type_index);
+    }
+
+    pub fn build(self) -> ModuleContext {
+        let ModuleContextBuilder {
+            memories,
+            tables,
+            globals,
+            types,
+            func_type_indexes,
+        } = self;
+
+        ModuleContext {
+            memories,
+            tables,
+            globals,
+            types,
+            func_type_indexes,
+        }
+    }
+}

validation/src/lib.rs

@@ -0,0 +1,449 @@
+// TODO: Uncomment
+// #![warn(missing_docs)]
+
+#![cfg_attr(not(feature = "std"), no_std)]
+
+#[cfg(not(feature = "std"))]
+#[macro_use]
+extern crate alloc;
+#[cfg(feature = "std")]
+extern crate std as alloc;
+
+pub mod stack;
+
+/// Index of default linear memory.
+pub const DEFAULT_MEMORY_INDEX: u32 = 0;
+/// Index of default table.
+pub const DEFAULT_TABLE_INDEX: u32 = 0;
+
+/// Maximal number of pages that a wasm instance supports.
+pub const LINEAR_MEMORY_MAX_PAGES: u32 = 65536;
+
+use alloc::{string::String, vec::Vec};
+use core::fmt;
+#[cfg(feature = "std")]
+use std::error;
+
+use self::context::ModuleContextBuilder;
+use parity_wasm::elements::{
+    BlockType, ExportEntry, External, FuncBody, GlobalEntry, GlobalType, InitExpr, Instruction,
+    Internal, MemoryType, Module, ResizableLimits, TableType, Type, ValueType,
+};
+
+pub mod context;
+pub mod func;
+pub mod util;
+
+#[cfg(test)]
+mod tests;
+
+// TODO: Consider using a type other than String, because
+// of formatting machinary is not welcomed in substrate runtimes.
+#[derive(Debug)]
+pub struct Error(pub String);
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self.0)
+    }
+}
+
+#[cfg(feature = "std")]
+impl error::Error for Error {
+    fn description(&self) -> &str {
+        &self.0
+    }
+}
+
+impl From<stack::Error> for Error {
+    fn from(e: stack::Error) -> Error {
+        Error(format!("Stack: {}", e))
+    }
+}
+
+pub trait Validator {
+    type Output;
+    type FuncValidator: FuncValidator;
+    fn new(module: &Module) -> Self;
+    fn on_function_validated(
+        &mut self,
+        index: u32,
+        output: <<Self as Validator>::FuncValidator as FuncValidator>::Output,
+    );
+    fn finish(self) -> Self::Output;
+}
+
+pub trait FuncValidator {
+    type Output;
+    fn new(ctx: &func::FunctionValidationContext, body: &FuncBody) -> Self;
+    fn next_instruction(
+        &mut self,
+        ctx: &mut func::FunctionValidationContext,
+        instruction: &Instruction,
+    ) -> Result<(), Error>;
+    fn finish(self) -> Self::Output;
+}
+
+/// A module validator that just validates modules and produces no result.
+pub struct PlainValidator;
+
+impl Validator for PlainValidator {
+    type Output = ();
+    type FuncValidator = PlainFuncValidator;
+    fn new(_module: &Module) -> PlainValidator {
+        PlainValidator
+    }
+    fn on_function_validated(
+        &mut self,
+        _index: u32,
+        _output: <<Self as Validator>::FuncValidator as FuncValidator>::Output,
+    ) -> () {
+        ()
+    }
+    fn finish(self) -> () {
+        ()
+    }
+}
+
+/// A function validator that just validates modules and produces no result.
+pub struct PlainFuncValidator;
+
+impl FuncValidator for PlainFuncValidator {
+    type Output = ();
+
+    fn new(_ctx: &func::FunctionValidationContext, _body: &FuncBody) -> PlainFuncValidator {
+        PlainFuncValidator
+    }
+
+    fn next_instruction(
+        &mut self,
+        ctx: &mut func::FunctionValidationContext,
+        instruction: &Instruction,
+    ) -> Result<(), Error> {
+        ctx.step(instruction)
+    }
+
+    fn finish(self) -> () {
+        ()
+    }
+}
+
+pub fn validate_module<V: Validator>(module: &Module) -> Result<V::Output, Error> {
+    let mut context_builder = ModuleContextBuilder::new();
+    let mut imported_globals = Vec::new();
+    let mut validation = V::new(&module);
+
+    // Copy types from module as is.
+    context_builder.set_types(
+        module
+            .type_section()
+            .map(|ts| {
+                ts.types()
+                    .into_iter()
+                    .map(|&Type::Function(ref ty)| ty)
+                    .cloned()
+                    .collect()
+            })
+            .unwrap_or_default(),
+    );
+
+    // Fill elements with imported values.
+    for import_entry in module
+        .import_section()
+        .map(|i| i.entries())
+        .unwrap_or_default()
+    {
+        match *import_entry.external() {
+            External::Function(idx) => context_builder.push_func_type_index(idx),
+            External::Table(ref table) => context_builder.push_table(table.clone()),
+            External::Memory(ref memory) => context_builder.push_memory(memory.clone()),
+            External::Global(ref global) => {
+                context_builder.push_global(global.clone());
+                imported_globals.push(global.clone());
+            }
+        }
+    }
+
+    // Concatenate elements with defined in the module.
+    if let Some(function_section) = module.function_section() {
+        for func_entry in function_section.entries() {
+            context_builder.push_func_type_index(func_entry.type_ref())
+        }
+    }
+    if let Some(table_section) = module.table_section() {
+        for table_entry in table_section.entries() {
+            validate_table_type(table_entry)?;
+            context_builder.push_table(table_entry.clone());
+        }
+    }
+    if let Some(mem_section) = module.memory_section() {
+        for mem_entry in mem_section.entries() {
+            validate_memory_type(mem_entry)?;
+            context_builder.push_memory(mem_entry.clone());
+        }
+    }
+    if let Some(global_section) = module.global_section() {
+        for global_entry in global_section.entries() {
+            validate_global_entry(global_entry, &imported_globals)?;
+            context_builder.push_global(global_entry.global_type().clone());
+        }
+    }
+
+    let context = context_builder.build();
+
+    let function_section_len = module
+        .function_section()
+        .map(|s| s.entries().len())
+        .unwrap_or(0);
+    let code_section_len = module.code_section().map(|s| s.bodies().len()).unwrap_or(0);
+    if function_section_len != code_section_len {
+        return Err(Error(format!(
+            "length of function section is {}, while len of code section is {}",
+            function_section_len, code_section_len
+        )));
+    }
+
+    // validate every function body in user modules
+    if function_section_len != 0 {
+        // tests use invalid code
+        let function_section = module
+            .function_section()
+            .expect("function_section_len != 0; qed");
+        let code_section = module
+            .code_section()
+            .expect("function_section_len != 0; function_section_len == code_section_len; qed");
+        // check every function body
+        for (index, function) in function_section.entries().iter().enumerate() {
+            let function_body = code_section
+                .bodies()
+                .get(index as usize)
+                .ok_or(Error(format!("Missing body for function {}", index)))?;
+
+            let output = func::drive::<V::FuncValidator>(&context, function, function_body)
+                .map_err(|Error(ref msg)| {
+                    Error(format!(
+                        "Function #{} reading/validation error: {}",
+                        index, msg
+                    ))
+                })?;
+            validation.on_function_validated(index as u32, output);
+        }
+    }
+
+    // validate start section
+    if let Some(start_fn_idx) = module.start_section() {
+        let (params, return_ty) = context.require_function(start_fn_idx)?;
+        if return_ty != BlockType::NoResult || params.len() != 0 {
+            return Err(Error(
+                "start function expected to have type [] -> []".into(),
+            ));
+        }
+    }
+
+    // validate export section
+    if let Some(export_section) = module.export_section() {
+        let mut export_names = export_section
+            .entries()
+            .iter()
+            .map(ExportEntry::field)
+            .collect::<Vec<_>>();
+
+        export_names.sort_unstable();
+
+        for (fst, snd) in export_names.iter().zip(export_names.iter().skip(1)) {
+            if fst == snd {
+                return Err(Error(format!("duplicate export {}", fst)));
+            }
+        }
+
+        for export in export_section.entries() {
+            match *export.internal() {
+                Internal::Function(function_index) => {
+                    context.require_function(function_index)?;
+                }
+                Internal::Global(global_index) => {
+                    context.require_global(global_index, Some(false))?;
+                }
+                Internal::Memory(memory_index) => {
+                    context.require_memory(memory_index)?;
+                }
+                Internal::Table(table_index) => {
+                    context.require_table(table_index)?;
+                }
+            }
+        }
+    }
+
+    // validate import section
+    if let Some(import_section) = module.import_section() {
+        for import in import_section.entries() {
+            match *import.external() {
+                External::Function(function_type_index) => {
+                    context.require_function_type(function_type_index)?;
+                }
+                External::Global(ref global_type) => {
+                    if global_type.is_mutable() {
+                        return Err(Error(format!(
+                            "trying to import mutable global {}",
+                            import.field()
+                        )));
+                    }
+                }
+                External::Memory(ref memory_type) => {
+                    validate_memory_type(memory_type)?;
+                }
+                External::Table(ref table_type) => {
+                    validate_table_type(table_type)?;
+                }
+            }
+        }
+    }
+
+    // there must be no greater than 1 table in tables index space
+    if context.tables().len() > 1 {
+        return Err(Error(format!(
+            "too many tables in index space: {}",
+            context.tables().len()
+        )));
+    }
+
+    // there must be no greater than 1 linear memory in memory index space
+    if context.memories().len() > 1 {
+        return Err(Error(format!(
+            "too many memory regions in index space: {}",
+            context.memories().len()
+        )));
+    }
+
+    // use data section to initialize linear memory regions
+    if let Some(data_section) = module.data_section() {
+        for data_segment in data_section.entries() {
+            context.require_memory(data_segment.index())?;
+            let offset = data_segment
+                .offset()
+                .as_ref()
+                .ok_or_else(|| Error("passive memory segments are not supported".into()))?;
+            let init_ty = expr_const_type(&offset, context.globals())?;
+            if init_ty != ValueType::I32 {
+                return Err(Error("segment offset should return I32".into()));
+            }
+        }
+    }
+
+    // use element section to fill tables
+    if let Some(element_section) = module.elements_section() {
+        for element_segment in element_section.entries() {
+            context.require_table(element_segment.index())?;
+            let offset = element_segment
+                .offset()
+                .as_ref()
+                .ok_or_else(|| Error("passive element segments are not supported".into()))?;
+            let init_ty = expr_const_type(&offset, context.globals())?;
+            if init_ty != ValueType::I32 {
+                return Err(Error("segment offset should return I32".into()));
+            }
+
+            for function_index in element_segment.members() {
+                context.require_function(*function_index)?;
+            }
+        }
+    }
+
+    Ok(validation.finish())
+}
+
+fn validate_limits(limits: &ResizableLimits) -> Result<(), Error> {
+    if let Some(maximum) = limits.maximum() {
+        if limits.initial() > maximum {
+            return Err(Error(format!(
+                "maximum limit {} is less than minimum {}",
+                maximum,
+                limits.initial()
+            )));
+        }
+    }
+    Ok(())
+}
+
+fn validate_memory_type(memory_type: &MemoryType) -> Result<(), Error> {
+    let initial = memory_type.limits().initial();
+    let maximum: Option<u32> = memory_type.limits().maximum();
+    validate_memory(initial, maximum).map_err(Error)
+}
+
+pub fn validate_memory(initial: u32, maximum: Option<u32>) -> Result<(), String> {
+    if initial > LINEAR_MEMORY_MAX_PAGES {
+        return Err(format!(
+            "initial memory size must be at most {} pages",
+            LINEAR_MEMORY_MAX_PAGES
+        ));
+    }
+    if let Some(maximum) = maximum {
+        if initial > maximum {
+            return Err(format!(
+                "maximum limit {} is less than minimum {}",
+                maximum, initial,
+            ));
+        }
+
+        if maximum > LINEAR_MEMORY_MAX_PAGES {
+            return Err(format!(
+                "maximum memory size must be at most {} pages",
+                LINEAR_MEMORY_MAX_PAGES
+            ));
+        }
+    }
+    Ok(())
+}
+
+fn validate_table_type(table_type: &TableType) -> Result<(), Error> {
+    validate_limits(table_type.limits())
+}
+
+fn validate_global_entry(global_entry: &GlobalEntry, globals: &[GlobalType]) -> Result<(), Error> {
+    let init = global_entry.init_expr();
+    let init_expr_ty = expr_const_type(init, globals)?;
+    if init_expr_ty != global_entry.global_type().content_type() {
+        return Err(Error(format!(
+            "Trying to initialize variable of type {:?} with value of type {:?}",
+            global_entry.global_type().content_type(),
+            init_expr_ty
+        )));
+    }
+    Ok(())
+}
+
+/// Returns type of this constant expression.
+fn expr_const_type(init_expr: &InitExpr, globals: &[GlobalType]) -> Result<ValueType, Error> {
+    let code = init_expr.code();
+    if code.len() != 2 {
+        return Err(Error(
+            "Init expression should always be with length 2".into(),
+        ));
+    }
+    let expr_ty: ValueType = match code[0] {
+        Instruction::I32Const(_) => ValueType::I32,
+        Instruction::I64Const(_) => ValueType::I64,
+        Instruction::F32Const(_) => ValueType::F32,
+        Instruction::F64Const(_) => ValueType::F64,
+        Instruction::GetGlobal(idx) => match globals.get(idx as usize) {
+            Some(target_global) => {
+                if target_global.is_mutable() {
+                    return Err(Error(format!("Global {} is mutable", idx)));
+                }
+                target_global.content_type()
+            }
+            None => {
+                return Err(Error(format!(
+                    "Global {} doesn't exists or not yet defined",
+                    idx
+                )));
+            }
+        },
+        _ => return Err(Error("Non constant opcode in init expr".into())),
+    };
+    if code[1] != Instruction::End {
+        return Err(Error("Expression doesn't ends with `end` opcode".into()));
+    }
+    Ok(expr_ty)
+}

validation/src/stack.rs

@@ -0,0 +1,100 @@
+use alloc::{string::String, vec::Vec};
+
+use core::fmt;
+#[cfg(feature = "std")]
+use std::error;
+
+#[derive(Debug)]
+pub struct Error(String);
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self.0)
+    }
+}
+
+#[cfg(feature = "std")]
+impl error::Error for Error {
+    fn description(&self) -> &str {
+        &self.0
+    }
+}
+
+/// Stack with limit.
+#[derive(Debug)]
+pub struct StackWithLimit<T>
+where
+    T: Clone,
+{
+    /// Stack values.
+    values: Vec<T>,
+    /// Stack limit (maximal stack len).
+    limit: usize,
+}
+
+impl<T> StackWithLimit<T>
+where
+    T: Clone,
+{
+    pub fn with_limit(limit: usize) -> Self {
+        StackWithLimit {
+            values: Vec::new(),
+            limit: limit,
+        }
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.values.is_empty()
+    }
+
+    pub fn len(&self) -> usize {
+        self.values.len()
+    }
+
+    pub fn top(&self) -> Result<&T, Error> {
+        self.values
+            .last()
+            .ok_or_else(|| Error("non-empty stack expected".into()))
+    }
+
+    pub fn top_mut(&mut self) -> Result<&mut T, Error> {
+        self.values
+            .last_mut()
+            .ok_or_else(|| Error("non-empty stack expected".into()))
+    }
+
+    pub fn get(&self, index: usize) -> Result<&T, Error> {
+        if index >= self.values.len() {
+            return Err(Error(format!(
+                "trying to get value at position {} on stack of size {}",
+                index,
+                self.values.len()
+            )));
+        }
+
+        Ok(self
+            .values
+            .get(self.values.len() - 1 - index)
+            .expect("checked couple of lines above"))
+    }
+
+    pub fn push(&mut self, value: T) -> Result<(), Error> {
+        if self.values.len() >= self.limit {
+            return Err(Error(format!("exceeded stack limit {}", self.limit)));
+        }
+
+        self.values.push(value);
+        Ok(())
+    }
+
+    pub fn pop(&mut self) -> Result<T, Error> {
+        self.values
+            .pop()
+            .ok_or_else(|| Error("non-empty stack expected".into()))
+    }
+
+    pub fn resize(&mut self, new_size: usize, dummy: T) {
+        debug_assert!(new_size <= self.values.len());
+        self.values.resize(new_size, dummy);
+    }
+}

validation/src/tests.rs

@@ -0,0 +1,277 @@
+use crate::{Error, PlainValidator};
+use parity_wasm::{
+    builder::module,
+    elements::{
+        BlockType, External, GlobalEntry, GlobalType, ImportEntry, InitExpr, Instruction,
+        Instructions, MemoryType, Module, TableType, ValueType,
+    },
+};
+
+fn validate_module(module: &Module) -> Result<(), Error> {
+    super::validate_module::<PlainValidator>(module)
+}
+
+#[test]
+fn empty_is_valid() {
+    let module = module().build();
+    assert!(validate_module(&module).is_ok());
+}
+
+#[test]
+fn limits() {
+    let test_cases = vec![
+        // min > max
+        (10, Some(9), false),
+        // min = max
+        (10, Some(10), true),
+        // table/memory is always valid without max
+        (10, None, true),
+    ];
+
+    for (min, max, is_valid) in test_cases {
+        // defined table
+        let m = module().table().with_min(min).with_max(max).build().build();
+        assert_eq!(validate_module(&m).is_ok(), is_valid);
+
+        // imported table
+        let m = module()
+            .with_import(ImportEntry::new(
+                "core".into(),
+                "table".into(),
+                External::Table(TableType::new(min, max)),
+            ))
+            .build();
+        assert_eq!(validate_module(&m).is_ok(), is_valid);
+
+        // defined memory
+        let m = module()
+            .memory()
+            .with_min(min)
+            .with_max(max)
+            .build()
+            .build();
+        assert_eq!(validate_module(&m).is_ok(), is_valid);
+
+        // imported table
+        let m = module()
+            .with_import(ImportEntry::new(
+                "core".into(),
+                "memory".into(),
+                External::Memory(MemoryType::new(min, max)),
+            ))
+            .build();
+        assert_eq!(validate_module(&m).is_ok(), is_valid);
+    }
+}
+
+#[test]
+fn global_init_const() {
+    let m = module()
+        .with_global(GlobalEntry::new(
+            GlobalType::new(ValueType::I32, true),
+            InitExpr::new(vec![Instruction::I32Const(42), Instruction::End]),
+        ))
+        .build();
+    assert!(validate_module(&m).is_ok());
+
+    // init expr type differs from declared global type
+    let m = module()
+        .with_global(GlobalEntry::new(
+            GlobalType::new(ValueType::I64, true),
+            InitExpr::new(vec![Instruction::I32Const(42), Instruction::End]),
+        ))
+        .build();
+    assert!(validate_module(&m).is_err());
+}
+
+#[test]
+fn global_init_global() {
+    let m = module()
+        .with_import(ImportEntry::new(
+            "env".into(),
+            "ext_global".into(),
+            External::Global(GlobalType::new(ValueType::I32, false)),
+        ))
+        .with_global(GlobalEntry::new(
+            GlobalType::new(ValueType::I32, true),
+            InitExpr::new(vec![Instruction::GetGlobal(0), Instruction::End]),
+        ))
+        .build();
+    assert!(validate_module(&m).is_ok());
+
+    // get_global can reference only previously defined globals
+    let m = module()
+        .with_global(GlobalEntry::new(
+            GlobalType::new(ValueType::I32, true),
+            InitExpr::new(vec![Instruction::GetGlobal(0), Instruction::End]),
+        ))
+        .build();
+    assert!(validate_module(&m).is_err());
+
+    // get_global can reference only const globals
+    let m = module()
+        .with_import(ImportEntry::new(
+            "env".into(),
+            "ext_global".into(),
+            External::Global(GlobalType::new(ValueType::I32, true)),
+        ))
+        .with_global(GlobalEntry::new(
+            GlobalType::new(ValueType::I32, true),
+            InitExpr::new(vec![Instruction::GetGlobal(0), Instruction::End]),
+        ))
+        .build();
+    assert!(validate_module(&m).is_err());
+
+    // get_global in init_expr can only refer to imported globals.
+    let m = module()
+        .with_global(GlobalEntry::new(
+            GlobalType::new(ValueType::I32, false),
+            InitExpr::new(vec![Instruction::I32Const(0), Instruction::End]),
+        ))
+        .with_global(GlobalEntry::new(
+            GlobalType::new(ValueType::I32, true),
+            InitExpr::new(vec![Instruction::GetGlobal(0), Instruction::End]),
+        ))
+        .build();
+    assert!(validate_module(&m).is_err());
+}
+
+#[test]
+fn global_init_misc() {
+    // without delimiting End opcode
+    let m = module()
+        .with_global(GlobalEntry::new(
+            GlobalType::new(ValueType::I32, true),
+            InitExpr::new(vec![Instruction::I32Const(42)]),
+        ))
+        .build();
+    assert!(validate_module(&m).is_err());
+
+    // empty init expr
+    let m = module()
+        .with_global(GlobalEntry::new(
+            GlobalType::new(ValueType::I32, true),
+            InitExpr::new(vec![Instruction::End]),
+        ))
+        .build();
+    assert!(validate_module(&m).is_err());
+
+    // not an constant opcode used
+    let m = module()
+        .with_global(GlobalEntry::new(
+            GlobalType::new(ValueType::I32, true),
+            InitExpr::new(vec![Instruction::Unreachable, Instruction::End]),
+        ))
+        .build();
+    assert!(validate_module(&m).is_err());
+}
+
+#[test]
+fn module_limits_validity() {
+    // module cannot contain more than 1 memory atm.
+    let m = module()
+        .with_import(ImportEntry::new(
+            "core".into(),
+            "memory".into(),
+            External::Memory(MemoryType::new(10, None)),
+        ))
+        .memory()
+        .with_min(10)
+        .build()
+        .build();
+    assert!(validate_module(&m).is_err());
+
+    // module cannot contain more than 1 table atm.
+    let m = module()
+        .with_import(ImportEntry::new(
+            "core".into(),
+            "table".into(),
+            External::Table(TableType::new(10, None)),
+        ))
+        .table()
+        .with_min(10)
+        .build()
+        .build();
+    assert!(validate_module(&m).is_err());
+}
+
+#[test]
+fn funcs() {
+    // recursive function calls is legal.
+    let m = module()
+        .function()
+        .signature()
+        .return_type()
+        .i32()
+        .build()
+        .body()
+        .with_instructions(Instructions::new(vec![
+            Instruction::Call(1),
+            Instruction::End,
+        ]))
+        .build()
+        .build()
+        .function()
+        .signature()
+        .return_type()
+        .i32()
+        .build()
+        .body()
+        .with_instructions(Instructions::new(vec![
+            Instruction::Call(0),
+            Instruction::End,
+        ]))
+        .build()
+        .build()
+        .build();
+    assert!(validate_module(&m).is_ok());
+}
+
+#[test]
+fn globals() {
+    // import immutable global is legal.
+    let m = module()
+        .with_import(ImportEntry::new(
+            "env".into(),
+            "ext_global".into(),
+            External::Global(GlobalType::new(ValueType::I32, false)),
+        ))
+        .build();
+    assert!(validate_module(&m).is_ok());
+
+    // import mutable global is invalid.
+    let m = module()
+        .with_import(ImportEntry::new(
+            "env".into(),
+            "ext_global".into(),
+            External::Global(GlobalType::new(ValueType::I32, true)),
+        ))
+        .build();
+    assert!(validate_module(&m).is_err());
+}
+
+#[test]
+fn if_else_with_return_type_validation() {
+    let m = module()
+        .function()
+        .signature()
+        .build()
+        .body()
+        .with_instructions(Instructions::new(vec![
+            Instruction::I32Const(1),
+            Instruction::If(BlockType::NoResult),
+            Instruction::I32Const(1),
+            Instruction::If(BlockType::Value(ValueType::I32)),
+            Instruction::I32Const(1),
+            Instruction::Else,
+            Instruction::I32Const(2),
+            Instruction::End,
+            Instruction::Drop,
+            Instruction::End,
+            Instruction::End,
+        ]))
+        .build()
+        .build()
+        .build();
+    validate_module(&m).unwrap();
+}

validation/src/util.rs

@@ -0,0 +1,130 @@
+use crate::Error;
+use alloc::string::String;
+use parity_wasm::elements::{Local, ValueType};
+
+#[cfg(test)]
+use assert_matches::assert_matches;
+
+/// Locals are the concatenation of a slice of function parameters
+/// with function declared local variables.
+///
+/// Local variables are given in the form of groups represented by pairs
+/// of a value_type and a count.
+#[derive(Debug)]
+pub struct Locals<'a> {
+    params: &'a [ValueType],
+    local_groups: &'a [Local],
+    count: u32,
+}
+
+impl<'a> Locals<'a> {
+    /// Create a new wrapper around declared variables and parameters.
+    pub fn new(params: &'a [ValueType], local_groups: &'a [Local]) -> Result<Locals<'a>, Error> {
+        let mut acc = params.len() as u32;
+        for locals_group in local_groups {
+            acc = acc
+                .checked_add(locals_group.count())
+                .ok_or_else(|| Error(String::from("Locals range not in 32-bit range")))?;
+        }
+
+        Ok(Locals {
+            params,
+            local_groups,
+            count: acc,
+        })
+    }
+
+    /// Returns parameter count.
+    pub fn param_count(&self) -> u32 {
+        self.params.len() as u32
+    }
+
+    /// Returns total count of all declared locals and paramaterers.
+    pub fn count(&self) -> u32 {
+        self.count
+    }
+
+    /// Returns the type of a local variable (either a declared local or a param).
+    ///
+    /// Returns `Err` in the case of overflow or when idx falls out of range.
+    pub fn type_of_local(&self, idx: u32) -> Result<ValueType, Error> {
+        if let Some(param) = self.params.get(idx as usize) {
+            return Ok(*param);
+        }
+
+        // If an index doesn't point to a param, then we have to look into local declarations.
+        let mut start_idx = self.param_count();
+        for locals_group in self.local_groups {
+            let end_idx = start_idx
+                .checked_add(locals_group.count())
+                .ok_or_else(|| Error(String::from("Locals range not in 32-bit range")))?;
+
+            if idx >= start_idx && idx < end_idx {
+                return Ok(locals_group.value_type());
+            }
+
+            start_idx = end_idx;
+        }
+
+        // We didn't find anything, that's an error.
+        // At this moment `start_idx` should hold the count of all locals
+        // (since it's either set to the `end_idx` or equal to `params.len()`)
+        let total_count = start_idx;
+
+        Err(Error(format!(
+            "Trying to access local with index {} when there are only {} locals",
+            idx, total_count
+        )))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn locals_it_works() {
+        let params = vec![ValueType::I32, ValueType::I64];
+        let local_groups = vec![Local::new(2, ValueType::F32), Local::new(2, ValueType::F64)];
+        let locals = Locals::new(&params, &local_groups).unwrap();
+
+        assert_matches!(locals.type_of_local(0), Ok(ValueType::I32));
+        assert_matches!(locals.type_of_local(1), Ok(ValueType::I64));
+        assert_matches!(locals.type_of_local(2), Ok(ValueType::F32));
+        assert_matches!(locals.type_of_local(3), Ok(ValueType::F32));
+        assert_matches!(locals.type_of_local(4), Ok(ValueType::F64));
+        assert_matches!(locals.type_of_local(5), Ok(ValueType::F64));
+        assert_matches!(locals.type_of_local(6), Err(_));
+    }
+
+    #[test]
+    fn locals_no_declared_locals() {
+        let params = vec![ValueType::I32];
+        let locals = Locals::new(&params, &[]).unwrap();
+
+        assert_matches!(locals.type_of_local(0), Ok(ValueType::I32));
+        assert_matches!(locals.type_of_local(1), Err(_));
+    }
+
+    #[test]
+    fn locals_no_params() {
+        let local_groups = vec![Local::new(2, ValueType::I32), Local::new(3, ValueType::I64)];
+        let locals = Locals::new(&[], &local_groups).unwrap();
+
+        assert_matches!(locals.type_of_local(0), Ok(ValueType::I32));
+        assert_matches!(locals.type_of_local(1), Ok(ValueType::I32));
+        assert_matches!(locals.type_of_local(2), Ok(ValueType::I64));
+        assert_matches!(locals.type_of_local(3), Ok(ValueType::I64));
+        assert_matches!(locals.type_of_local(4), Ok(ValueType::I64));
+        assert_matches!(locals.type_of_local(5), Err(_));
+    }
+
+    #[test]
+    fn locals_u32_overflow() {
+        let local_groups = vec![
+            Local::new(u32::max_value(), ValueType::I32),
+            Local::new(1, ValueType::I64),
+        ];
+        assert_matches!(Locals::new(&[], &local_groups), Err(_));
+    }
+}