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 --git https://github.com/deadlinks/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 = "0.4.1"
+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 = "0.31"
-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 = "0.4"
+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

@@ -3,18 +3,11 @@
 
 # `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.
-
-# License
-
-`wasmi` is primarily distributed under the terms of both the MIT
-license and the Apache License (Version 2.0), at your choice.
-
-See LICENSE-APACHE, and LICENSE-MIT for details.
+With all that said, `wasmi` should be a good option for initial prototyping.
 
 # Build & Test
 
@@ -27,6 +20,32 @@ 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
+
+`wasmi` is primarily distributed under the terms of both the MIT
+license and the Apache License (Version 2.0), at your choice.
+
+See LICENSE-APACHE, and LICENSE-MIT for details.
+
 ## Contribution
 
 Unless you explicitly state otherwise, any contribution intentionally submitted

benches/Cargo.toml

@@ -6,7 +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

@@ -1,7 +1,6 @@
 use std::env;
 use std::process;
 
-
 fn main() {
     println!("cargo:rerun-if-changed=./wasm-kernel/");
 
@@ -23,9 +22,9 @@ fn main() {
     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),
+            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

@@ -4,7 +4,7 @@ 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::*;
@@ -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

@@ -1,14 +1,13 @@
-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)]
@@ -64,9 +63,7 @@ mod tictactoe {
 
     impl Game {
         pub fn new() -> Game {
-			Game {
-				board: [None; 9],
-			}
+            Game { board: [None; 9] }
         }
 
         pub fn set(&mut self, idx: i32, player: Player) -> Result<(), Error> {
@@ -96,12 +93,10 @@ mod tictactoe {
                 (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),
@@ -161,7 +156,7 @@ impl<'a> Externals for Runtime<'a> {
                 let val: i32 = tictactoe::Player::into_i32(self.game.get(idx)?);
                 Ok(Some(val.into()))
             }
-			_ => panic!("unknown function index")
+            _ => panic!("unknown function index"),
         }
     }
 }
@@ -175,15 +170,20 @@ impl<'a> ModuleImportResolver for RuntimeModuleImportResolver {
         _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)
-				)
-			)
+            "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)
     }
@@ -201,8 +201,7 @@ fn instantiate(path: &str) -> Result<ModuleRef, Error> {
     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)
 }

fuzz/Cargo.toml

@@ -10,7 +10,7 @@ cargo-fuzz = true
 
 [dependencies]
 wasmi = { path = ".." }
-wabt = "0.2.0"
+wabt = "0.9"
 wasmparser = "0.14.1"
 tempdir = "0.3.6"
 

hfuzz/Cargo.toml

@@ -7,4 +7,4 @@ authors = ["Sergey Pepyakin <s.pepyakin@gmail.com>"]
 honggfuzz = "=0.5.9" # Strict equal since hfuzz requires dep and cmd versions to match.
 wasmi = { path = ".." }
 tempdir = "0.3.6"
-wabt = "0.2.0"
+wabt = "0.9"

src/bin/instantiate.rs

@@ -5,12 +5,12 @@ 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::*;
@@ -46,7 +46,8 @@ impl ModuleImportResolver for ResolveAll {
         Ok(MemoryInstance::alloc(
             Pages(memory_type.initial() as usize),
             memory_type.maximum().map(|m| Pages(m as usize)),
-		).unwrap())
+        )
+        .unwrap())
     }
 
     fn resolve_table(
@@ -75,7 +76,8 @@ fn main() {
             .with_resolver("global.Math", &ResolveAll)
             .with_resolver("asm2wasm", &ResolveAll)
             .with_resolver("spectest", &ResolveAll),
-	).expect("Failed to instantiate module")
+    )
+    .expect("Failed to instantiate module")
     .run_start(&mut NopExternals)
     .expect("Failed to run start function in module");
 }

src/common/mod.rs

@@ -1,9 +0,0 @@
-
-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;
-
-// TODO: Move BlockFrame under validation.

src/common/stack.rs

@@ -1,84 +0,0 @@
-
-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: 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);
-	}
-}

src/func.rs

@@ -1,13 +1,17 @@
-use std::rc::{Rc, Weak};
-use std::fmt;
-use parity_wasm::elements::Local;
-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, InterpreterState};
-use value::RuntimeValue;
-use types::ValueType;
-use module::ModuleInstance;
 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).
 ///
@@ -17,7 +21,7 @@ use isa;
 #[derive(Clone, Debug)]
 pub struct FuncRef(Rc<FuncInstance>);
 
-impl ::std::ops::Deref for FuncRef {
+impl ::core::ops::Deref for FuncRef {
     type Target = FuncInstance;
     fn deref(&self) -> &FuncInstance {
         &self.0
@@ -56,17 +60,10 @@ pub(crate) enum FuncInstanceInternal {
 impl fmt::Debug for FuncInstance {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match self.as_internal() {
-			&FuncInstanceInternal::Internal {
-				ref signature,
-				..
-			} => {
+            &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,
-				)
+                write!(f, "Internal {{ signature={:?} }}", signature,)
             }
             &FuncInstanceInternal::Host { ref signature, .. } => {
                 write!(f, "Host {{ signature={:?} }}", signature)
@@ -142,10 +139,10 @@ impl FuncInstance {
         args: &[RuntimeValue],
         externals: &mut E,
     ) -> Result<Option<RuntimeValue>, Trap> {
-		check_function_args(func.signature(), &args).map_err(|_| TrapKind::UnexpectedSignature)?;
+        check_function_args(func.signature(), &args)?;
         match *func.as_internal() {
             FuncInstanceInternal::Internal { .. } => {
-				let mut interpreter = Interpreter::new(func, args)?;
+                let mut interpreter = Interpreter::new(func, args, None)?;
                 interpreter.start_execution(externals)
             }
             FuncInstanceInternal::Host {
@@ -155,6 +152,34 @@ impl FuncInstance {
         }
     }
 
+    /// 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.
@@ -171,12 +196,13 @@ impl FuncInstance {
     /// [`resume_execution`]: struct.FuncInvocation.html#method.resume_execution
     pub fn invoke_resumable<'args>(
         func: &FuncRef,
-		args: &'args [RuntimeValue],
+        args: impl Into<Cow<'args, [RuntimeValue]>>,
     ) -> Result<FuncInvocation<'args>, Trap> {
-		check_function_args(func.signature(), &args).map_err(|_| TrapKind::UnexpectedSignature)?;
+        let args = args.into();
+        check_function_args(func.signature(), &args)?;
         match *func.as_internal() {
             FuncInstanceInternal::Internal { .. } => {
-				let interpreter = Interpreter::new(func, args)?;
+                let interpreter = Interpreter::new(func, &*args, None)?;
                 Ok(FuncInvocation {
                     kind: FuncInvocationKind::Internal(interpreter),
                 })
@@ -184,15 +210,13 @@ impl FuncInstance {
             FuncInstanceInternal::Host {
                 ref host_func_index,
                 ..
-			} => {
-				Ok(FuncInvocation {
+            } => Ok(FuncInvocation {
                 kind: FuncInvocationKind::Host {
                     args,
                     host_func_index: *host_func_index,
                     finished: false,
                 },
-				})
-			},
+            }),
         }
     }
 }
@@ -235,9 +259,9 @@ pub struct FuncInvocation<'args> {
 enum FuncInvocationKind<'args> {
     Internal(Interpreter),
     Host {
-		args: &'args [RuntimeValue],
+        args: Cow<'args, [RuntimeValue]>,
         host_func_index: usize,
-		finished: bool
+        finished: bool,
     },
 }
 
@@ -253,32 +277,37 @@ impl<'args> FuncInvocation<'args> {
     /// 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() {
+            &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> {
+    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 } => {
+            }
+            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.clone().into())?)
-			},
+                Ok(externals.invoke_index(*host_func_index, args.as_ref().into())?)
+            }
         }
     }
 
@@ -290,17 +319,28 @@ impl<'args> FuncInvocation<'args> {
     ///
     /// [`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> {
-		match self.kind {
-			FuncInvocationKind::Internal(ref mut interpreter) => {
-				if !interpreter.state().is_resumable() {
-					return Err(ResumableError::AlreadyStarted);
+    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)?)
-			},
-			FuncInvocationKind::Host { .. } => {
-				return Err(ResumableError::NotResumable);
-			},
+                } else {
+                    Err(ResumableError::AlreadyStarted)
+                }
+            }
+            FuncInvocationKind::Host { .. } => Err(ResumableError::NotResumable),
         }
     }
 }

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).
 ///
@@ -13,7 +13,7 @@ use parity_wasm::elements::{ValueType as EValueType};
 #[derive(Clone, Debug)]
 pub struct GlobalRef(Rc<GlobalInstance>);
 
-impl ::std::ops::Deref for GlobalRef {
+impl ::core::ops::Deref for GlobalRef {
     type Target = GlobalInstance;
     fn deref(&self) -> &GlobalInstance {
         &self.0
@@ -57,7 +57,9 @@ impl GlobalInstance {
     /// 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()));
+            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()));

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.
@@ -27,8 +27,14 @@ impl<'a> RuntimeArgs<'a> {
     /// # 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)?)
+    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`.
@@ -50,7 +56,10 @@ impl<'a> RuntimeArgs<'a> {
     /// # Panics
     ///
     /// Panics if cast is invalid or not enough arguments.
-	pub fn nth<T>(&self, idx: usize) -> T where T: FromRuntimeValue {
+    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")
     }
@@ -98,18 +107,18 @@ impl<'a> RuntimeArgs<'a> {
 ///     _ => panic!(),
 /// }
 /// ```
-pub trait HostError: 'static + ::std::fmt::Display + ::std::fmt::Debug + Send + Sync {
+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 {
+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 HostError as *const T)) }
+            unsafe { Some(&*(self as *const dyn HostError as *const T)) }
         } else {
             None
         }
@@ -119,7 +128,7 @@ impl HostError {
     /// 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)) }
+            unsafe { Some(&mut *(self as *mut dyn HostError as *mut T)) }
         } else {
             None
         }
@@ -190,9 +199,15 @@ 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,
 ///         ))
 ///     }
 /// }
@@ -225,8 +240,8 @@ impl Externals for NopExternals {
 #[cfg(test)]
 mod tests {
 
+    use super::{HostError, RuntimeArgs};
     use value::RuntimeValue;
-	use super::{RuntimeArgs, HostError};
 
     #[test]
     fn i32_runtime_args() {
@@ -242,6 +257,5 @@ mod tests {
     }
 
     // Tests that `HostError` trait is object safe.
-	fn _host_error_is_object_safe(_: &HostError) {
-	}
+    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.
@@ -20,7 +20,6 @@ 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.
@@ -101,7 +100,7 @@ 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> {
@@ -113,14 +112,16 @@ impl<'a> Default for ImportsBuilder<'a> {
 impl<'a> ImportsBuilder<'a> {
     /// Create an empty `ImportsBuilder`.
     pub fn new() -> ImportsBuilder<'a> {
-		ImportsBuilder { modules: HashMap::new() }
+        ImportsBuilder {
+            modules: BTreeMap::new(),
+        }
     }
 
     /// Register an resolver by a name.
     pub fn with_resolver<N: Into<String>>(
         mut self,
         name: N,
-		resolver: &'a ModuleImportResolver,
+        resolver: &'a dyn ModuleImportResolver,
     ) -> Self {
         self.modules.insert(name.into(), resolver);
         self
@@ -129,11 +130,15 @@ impl<'a> ImportsBuilder<'a> {
     /// Register an resolver by a name.
     ///
     /// Mutable borrowed version.
-	pub fn push_resolver<N: Into<String>>(&mut self, name: N, resolver: &'a ModuleImportResolver) {
+    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> {
+    fn resolver(&self, name: &str) -> Option<&dyn ModuleImportResolver> {
         self.modules.get(name).cloned()
     }
 }
@@ -145,9 +150,9 @@ impl<'a> ImportResolver for ImportsBuilder<'a> {
         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)
+        self.resolver(module_name)
+            .ok_or_else(|| Error::Instantiation(format!("Module {} not found", module_name)))?
+            .resolve_func(field_name, signature)
     }
 
     fn resolve_global(
@@ -156,9 +161,9 @@ impl<'a> ImportResolver for ImportsBuilder<'a> {
         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)
+        self.resolver(module_name)
+            .ok_or_else(|| Error::Instantiation(format!("Module {} not found", module_name)))?
+            .resolve_global(field_name, global_type)
     }
 
     fn resolve_memory(
@@ -167,9 +172,9 @@ impl<'a> ImportResolver for ImportsBuilder<'a> {
         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)
+        self.resolver(module_name)
+            .ok_or_else(|| Error::Instantiation(format!("Module {} not found", module_name)))?
+            .resolve_memory(field_name, memory_type)
     }
 
     fn resolve_table(
@@ -178,9 +183,9 @@ impl<'a> ImportResolver for ImportsBuilder<'a> {
         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)
+        self.resolver(module_name)
+            .ok_or_else(|| Error::Instantiation(format!("Module {} not found", module_name)))?
+            .resolve_table(field_name, table_type)
     }
 }
 
@@ -193,14 +198,11 @@ pub trait ModuleImportResolver {
     /// 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),
-		))
+    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.
@@ -213,9 +215,10 @@ pub trait ModuleImportResolver {
         field_name: &str,
         _global_type: &GlobalDescriptor,
     ) -> Result<GlobalRef, Error> {
-		Err(Error::Instantiation(
-			format!("Export {} not found", field_name),
-		))
+        Err(Error::Instantiation(format!(
+            "Export {} not found",
+            field_name
+        )))
     }
 
     /// Resolve a memory.
@@ -228,9 +231,10 @@ pub trait ModuleImportResolver {
         field_name: &str,
         _memory_type: &MemoryDescriptor,
     ) -> Result<MemoryRef, Error> {
-		Err(Error::Instantiation(
-			format!("Export {} not found", field_name),
-		))
+        Err(Error::Instantiation(format!(
+            "Export {} not found",
+            field_name
+        )))
     }
 
     /// Resolve a table.
@@ -243,22 +247,18 @@ pub trait ModuleImportResolver {
         field_name: &str,
         _table_type: &TableDescriptor,
     ) -> Result<TableRef, Error> {
-		Err(Error::Instantiation(
-			format!("Export {} not found", field_name),
-		))
+        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))
-			})?
+    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(|| {
@@ -271,10 +271,9 @@ impl ModuleImportResolver for ModuleRef {
         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))
-			})?
+        Ok(self
+            .export_by_name(field_name)
+            .ok_or_else(|| Error::Instantiation(format!("Export {} not found", field_name)))?
             .as_global()
             .cloned()
             .ok_or_else(|| {
@@ -287,10 +286,9 @@ impl ModuleImportResolver for ModuleRef {
         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))
-			})?
+        Ok(self
+            .export_by_name(field_name)
+            .ok_or_else(|| Error::Instantiation(format!("Export {} not found", field_name)))?
             .as_memory()
             .cloned()
             .ok_or_else(|| {
@@ -303,14 +301,11 @@ impl ModuleImportResolver for ModuleRef {
         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))
-			})?
+        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))
-			})?)
+            .ok_or_else(|| Error::Instantiation(format!("Export {} is not a table", field_name)))?)
     }
 }

src/isa.rs

@@ -67,11 +67,12 @@
 //! - 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.
-#[repr(u8)]
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub enum Keep {
     None,
@@ -80,6 +81,16 @@ pub enum Keep {
     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 {
@@ -87,30 +98,46 @@ pub struct DropKeep {
     pub keep: Keep,
 }
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub struct Target {
     pub dst_pc: u32,
     pub drop_keep: DropKeep,
 }
 
 /// A relocation entry that specifies.
-#[derive(Debug)]
+#[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,
-	},
+    Br { pc: u32 },
     /// Patch the specified destination index inside of br_table instruction at
     /// the specified pc.
-	BrTable {
-		pc: u32,
-		idx: usize,
-	},
+    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 {
+pub enum Instruction<'a> {
     /// Push a local variable or an argument from the specified depth.
     GetLocal(u32),
 
@@ -135,7 +162,202 @@ pub enum Instruction {
     /// 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(Box<[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),
@@ -315,7 +537,7 @@ pub enum Instruction {
 
 #[derive(Debug, Clone)]
 pub struct Instructions {
-	vec: Vec<Instruction>,
+    vec: Vec<InstructionInternal>,
 }
 
 impl Instructions {
@@ -329,27 +551,27 @@ impl Instructions {
         self.vec.len() as u32
     }
 
-	pub fn push(&mut self, instruction: Instruction) {
+    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] {
-				Instruction::Br(ref mut target)
-				| Instruction::BrIfEqz(ref mut target)
-				| Instruction::BrIfNez(ref mut target) => target.dst_pc = dst_pc,
+                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 self.vec[pc as usize] {
-				Instruction::BrTable(ref mut targets) => targets[idx].dst_pc = dst_pc,
+            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{
+        InstructionIter {
             instructions: &self.vec,
             position,
         }
@@ -357,7 +579,7 @@ impl Instructions {
 }
 
 pub struct InstructionIter<'a> {
-	instructions: &'a [Instruction],
+    instructions: &'a [InstructionInternal],
     position: u32,
 }
 
@@ -369,13 +591,212 @@ impl<'a> InstructionIter<'a> {
 }
 
 impl<'a> Iterator for InstructionIter<'a> {
-	type Item = &'a Instruction;
+    type Item = Instruction<'a>;
 
     #[inline]
-	fn next(&mut self) -> Option<<Self as Iterator>::Item> {
-		self.instructions.get(self.position as usize).map(|instruction| {
+    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;
-			instruction
-		})
+
+        Some(out)
     }
 }

src/lib.rs

@@ -1,10 +1,10 @@
 //! # wasmi
 //!
-//! This library allows to load WebAssembly modules in binary format and invoke their functions.
+//! This library allows WebAssembly modules to be loaded in binary format and their functions invoked.
 //!
 //! # Introduction
 //!
-//! WebAssembly (wasm) is a safe, portable and 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 the form of modules that contains definitions of:
 //!
@@ -20,15 +20,15 @@
 //!
 //! ## Loading and Validation
 //!
-//! Before execution, a module must 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.
 //!
-//! A valid module can't access memory out of its sandbox, can't cause stack underflows
+//! A valid module can't access memory outside its sandbox, can't cause stack underflows
 //! and can only call functions with correct signatures.
 //!
 //! ## Instantiation
 //!
-//! In order to execute code from a wasm module, it must be instatiated.
+//! In order to execute code from a wasm module, it must be instantiated.
 //! Instantiation includes the following steps:
 //!
 //! 1. Creating an empty module instance.
@@ -95,22 +95,43 @@
 //! ```
 
 #![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 parity_wasm;
 
-pub extern crate nan_preserving_float;
+extern crate wasmi_validation as validation;
 
-use std::fmt;
+use alloc::{
+    boxed::Box,
+    string::{String, ToString},
+    vec::Vec,
+};
+use core::fmt;
+#[cfg(feature = "std")]
 use std::error;
 
+#[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.
@@ -138,6 +159,7 @@ impl fmt::Display for Trap {
     }
 }
 
+#[cfg(feature = "std")]
 impl error::Error for Trap {
     fn description(&self) -> &str {
         "runtime trap"
@@ -218,7 +240,7 @@ pub enum TrapKind {
     /// Typically returned from an implementation of [`Externals`].
     ///
     /// [`Externals`]: trait.Externals.html
-	Host(Box<host::HostError>),
+    Host(Box<dyn host::HostError>),
 }
 
 impl TrapKind {
@@ -252,7 +274,7 @@ pub enum Error {
     /// Trap.
     Trap(Trap),
     /// Custom embedder error.
-	Host(Box<host::HostError>),
+    Host(Box<dyn host::HostError>),
 }
 
 impl Error {
@@ -264,13 +286,13 @@ impl Error {
     /// [`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> {
+    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,
         }
     }
@@ -308,6 +330,7 @@ impl fmt::Display for Error {
     }
 }
 
+#[cfg(feature = "std")]
 impl error::Error for Error {
     fn description(&self) -> &str {
         match *self {
@@ -324,13 +347,19 @@ impl error::Error for Error {
     }
 }
 
-impl<U> From<U> for Error where U: host::HostError + Sized {
+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 {
+impl<U> From<U> for Trap
+where
+    U: host::HostError + Sized,
+{
     fn from(e: U) -> Self {
         Trap::new(TrapKind::Host(Box::new(e)))
     }
@@ -354,37 +383,38 @@ impl From<validation::Error> for Error {
     }
 }
 
-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 types;
 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, FuncInvocation, ResumableError};
-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::{size_of, ByteSize, Bytes, RoundUpTo};
 }
 
 /// Deserialized module prepared for instantiation.
@@ -427,16 +457,9 @@ impl Module {
     /// }
     /// ```
     pub fn from_parity_wasm_module(module: parity_wasm::elements::Module) -> Result<Module, Error> {
-		use validation::{validate_module, ValidatedModule};
-		let ValidatedModule {
-			code_map,
-			module,
-		} = validate_module(module)?;
+        let prepare::CompiledModule { code_map, module } = prepare::compile_module(module)?;
 
-		Ok(Module {
-			code_map,
-			module,
-		})
+        Ok(Module { code_map, module })
     }
 
     /// Fail if the module contains any floating-point operations
@@ -496,7 +519,7 @@ impl Module {
     /// 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)
+        prepare::deny_floating_point(&self.module).map_err(Into::into)
     }
 
     /// Create `Module` from a given buffer.

src/memory.rs

@@ -1,643 +0,0 @@
-use std::u32;
-use std::ops::Range;
-use std::cmp;
-use std::fmt;
-use std::rc::Rc;
-use std::cell::{Cell, RefCell};
-use parity_wasm::elements::ResizableLimits;
-use Error;
-use memory_units::{RoundUpTo, Pages, Bytes};
-use value::LittleEndianConvert;
-
-/// 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 with lazy allocation.
-	buffer: RefCell<Vec<u8>>,
-	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> {
-		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::with_capacity(4096)),
-			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.current_size.get()).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, ::std::mem::size_of::<T>())?;
-		Ok(T::from_little_endian(&buffer[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[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[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[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, ::std::mem::size_of::<T>())?.range();
-		value.into_little_endian(&mut buffer[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(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,
-			)));
-		}
-
-		let new_buffer_length: Bytes = new_size.into();
-		self.current_size.set(new_buffer_length.0);
-		Ok(size_before_grow)
-	}
-
-	fn checked_region<B>(&self, buffer: &mut B, offset: usize, size: usize) -> Result<CheckedRegion, Error>
-		where B: ::std::ops::DerefMut<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 <= self.current_size.get() && buffer.len() < end {
-			buffer.resize(end, 0);
-		}
-
-		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<B>(&self, buffer: &mut B, offset1: usize, size1: usize, offset2: usize, size2: usize)
-		-> Result<(CheckedRegion, CheckedRegion), Error>
-		where B: ::std::ops::DerefMut<Target=Vec<u8>>
-	{
-		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)))?;
-
-		let max = cmp::max(end1, end2);
-		if max <= self.current_size.get() && buffer.len() < max {
-			buffer.resize(max, 0);
-		}
-
-		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 { ::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 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 { ::std::ptr::copy_nonoverlapping(
-			buffer[read_region.range()].as_ptr(),
-			buffer[write_region.range()].as_ptr() as *mut _,
-			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[dst_range].copy_from_slice(&src_buffer[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[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. Note that the buffer size may be arbitraty. 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. Note that the buffer size may be arbitraty.
-	/// The closure may however resize it. Proceed with caution.
-	///
-	/// [`get`]: #method.get
-	/// [`set`]: #method.set
-	/// [`copy`]: #method.copy
-	pub fn with_direct_access_mut<R, F: FnOnce(&mut Vec<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::{MemoryRef, MemoryInstance, LINEAR_MEMORY_PAGE_SIZE};
-	use std::rc::Rc;
-	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 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);
-		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(), 101);
-			buf[..10].copy_from_slice(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
-		});
-		mem.with_direct_access(|buf| {
-			assert_eq!(buf.len(), 101);
-			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/module.rs

@@ -1,20 +1,28 @@
-use runner::check_function_args;
+use alloc::{
+    borrow::ToOwned,
+    rc::Rc,
+    string::{String, ToString},
+    vec::Vec,
+};
+use core::cell::RefCell;
+use core::fmt;
 use Trap;
-use std::rc::Rc;
-use std::cell::RefCell;
-use std::fmt;
-use std::collections::HashMap;
-use parity_wasm::elements::{External, InitExpr, Internal, Instruction, ResizableLimits, Type};
-use {Module, Error, Signature, MemoryInstance, RuntimeValue, TableInstance};
-use imports::ImportResolver;
+
+use alloc::collections::BTreeMap;
+
+use core::cell::Ref;
+use func::{FuncBody, FuncInstance, FuncRef};
 use global::{GlobalInstance, GlobalRef};
-use func::{FuncRef, FuncBody, FuncInstance};
-use table::TableRef;
-use memory::MemoryRef;
 use host::Externals;
-use common::{DEFAULT_MEMORY_INDEX, DEFAULT_TABLE_INDEX};
-use types::{GlobalDescriptor, TableDescriptor, MemoryDescriptor};
+use imports::ImportResolver;
+use memory::MemoryRef;
 use memory_units::Pages;
+use parity_wasm::elements::{External, InitExpr, Instruction, Internal, ResizableLimits, Type};
+use runner::StackRecycler;
+use table::TableRef;
+use types::{GlobalDescriptor, MemoryDescriptor, TableDescriptor};
+use validation::{DEFAULT_MEMORY_INDEX, DEFAULT_TABLE_INDEX};
+use {Error, MemoryInstance, Module, RuntimeValue, Signature, TableInstance};
 
 /// Reference to a [`ModuleInstance`].
 ///
@@ -32,7 +40,7 @@ use memory_units::Pages;
 #[derive(Clone, Debug)]
 pub struct ModuleRef(pub(crate) Rc<ModuleInstance>);
 
-impl ::std::ops::Deref for ModuleRef {
+impl ::core::ops::Deref for ModuleRef {
     type Target = ModuleInstance;
     fn deref(&self) -> &ModuleInstance {
         &self.0
@@ -154,7 +162,7 @@ pub struct ModuleInstance {
     funcs: RefCell<Vec<FuncRef>>,
     memories: RefCell<Vec<MemoryRef>>,
     globals: RefCell<Vec<GlobalRef>>,
-	exports: RefCell<HashMap<String, ExternVal>>,
+    exports: RefCell<BTreeMap<String, ExternVal>>,
 }
 
 impl ModuleInstance {
@@ -165,7 +173,7 @@ impl ModuleInstance {
             tables: RefCell::new(Vec::new()),
             memories: RefCell::new(Vec::new()),
             globals: RefCell::new(Vec::new()),
-			exports: RefCell::new(HashMap::new()),
+            exports: RefCell::new(BTreeMap::new()),
         }
     }
 
@@ -209,6 +217,12 @@ impl ModuleInstance {
         self.globals.borrow_mut().push(global)
     }
 
+    /// Access all globals. This is a non-standard API so it's unlikely to be
+    /// portable to other engines.
+    pub fn globals<'a>(&self) -> Ref<Vec<GlobalRef>> {
+        self.globals.borrow()
+    }
+
     fn insert_export<N: Into<String>>(&self, name: N, extern_val: ExternVal) {
         self.exports.borrow_mut().insert(name.into(), extern_val);
     }
@@ -248,9 +262,9 @@ impl ModuleInstance {
 
                 match (import.external(), extern_val) {
                     (&External::Function(fn_type_idx), &ExternVal::Func(ref func)) => {
-						let expected_fn_type = instance.signature_by_index(fn_type_idx).expect(
-							"Due to validation function type should exists",
-						);
+                        let expected_fn_type = instance
+                            .signature_by_index(fn_type_idx)
+                            .expect("Due to validation function type should exists");
                         let actual_fn_type = func.signature();
                         if &*expected_fn_type != actual_fn_type {
                             return Err(Error::Instantiation(format!(
@@ -283,8 +297,7 @@ impl ModuleInstance {
                     (expected_import, actual_extern_val) => {
                         return Err(Error::Instantiation(format!(
                             "Expected {:?} type, but provided {:?} extern_val",
-							expected_import,
-							actual_extern_val
+                            expected_import, actual_extern_val
                         )));
                     }
                 }
@@ -293,9 +306,10 @@ impl ModuleInstance {
 
         let code = loaded_module.code();
         {
-			let funcs = module.function_section().map(|fs| fs.entries()).unwrap_or(
-				&[],
-			);
+            let funcs = module
+                .function_section()
+                .map(|fs| fs.entries())
+                .unwrap_or(&[]);
             let bodies = module.code_section().map(|cs| cs.bodies()).unwrap_or(&[]);
             debug_assert!(
                 funcs.len() == bodies.len(),
@@ -305,9 +319,9 @@ impl ModuleInstance {
             for (index, (ty, body)) in
                 Iterator::zip(funcs.into_iter(), bodies.into_iter()).enumerate()
             {
-				let signature = instance.signature_by_index(ty.type_ref()).expect(
-					"Due to validation type should exists",
-				);
+                let signature = instance
+                    .signature_by_index(ty.type_ref())
+                    .expect("Due to validation type should exists");
                 let code = code.get(index).expect(
 					"At func validation time labels are collected; Collected labels are added by index; qed",
 				).clone();
@@ -322,16 +336,15 @@ impl ModuleInstance {
         }
 
         for table_type in module.table_section().map(|ts| ts.entries()).unwrap_or(&[]) {
-			let table = TableInstance::alloc(
-				table_type.limits().initial(),
-				table_type.limits().maximum(),
-			)?;
+            let table =
+                TableInstance::alloc(table_type.limits().initial(), table_type.limits().maximum())?;
             instance.push_table(table);
         }
 
-		for memory_type in module.memory_section().map(|ms| ms.entries()).unwrap_or(
-			&[],
-		)
+        for memory_type in module
+            .memory_section()
+            .map(|ms| ms.entries())
+            .unwrap_or(&[])
         {
             let initial: Pages = Pages(memory_type.limits().initial() as usize);
             let maximum: Option<Pages> = memory_type.limits().maximum().map(|m| Pages(m as usize));
@@ -341,46 +354,45 @@ impl ModuleInstance {
             instance.push_memory(memory);
         }
 
-		for global_entry in module.global_section().map(|gs| gs.entries()).unwrap_or(
-			&[],
-		)
+        for global_entry in module
+            .global_section()
+            .map(|gs| gs.entries())
+            .unwrap_or(&[])
         {
             let init_val = eval_init_expr(global_entry.init_expr(), &*instance);
-			let global = GlobalInstance::alloc(
-				init_val,
-				global_entry.global_type().is_mutable(),
-			);
+            let global = GlobalInstance::alloc(init_val, global_entry.global_type().is_mutable());
             instance.push_global(global);
         }
 
-		for export in module.export_section().map(|es| es.entries()).unwrap_or(
-			&[],
-		)
+        for export in module
+            .export_section()
+            .map(|es| es.entries())
+            .unwrap_or(&[])
         {
             let field = export.field();
             let extern_val: ExternVal = match *export.internal() {
                 Internal::Function(idx) => {
-					let func = instance.func_by_index(idx).expect(
-						"Due to validation func should exists",
-					);
+                    let func = instance
+                        .func_by_index(idx)
+                        .expect("Due to validation func should exists");
                     ExternVal::Func(func)
                 }
                 Internal::Global(idx) => {
-					let global = instance.global_by_index(idx).expect(
-						"Due to validation global should exists",
-					);
+                    let global = instance
+                        .global_by_index(idx)
+                        .expect("Due to validation global should exists");
                     ExternVal::Global(global)
                 }
                 Internal::Memory(idx) => {
-					let memory = instance.memory_by_index(idx).expect(
-						"Due to validation memory should exists",
-					);
+                    let memory = instance
+                        .memory_by_index(idx)
+                        .expect("Due to validation memory should exists");
                     ExternVal::Memory(memory)
                 }
                 Internal::Table(idx) => {
-					let table = instance.table_by_index(idx).expect(
-						"Due to validation table should exists",
-					);
+                    let table = instance
+                        .table_by_index(idx)
+                        .expect("Due to validation table should exists");
                     ExternVal::Table(table)
                 }
             };
@@ -404,45 +416,56 @@ impl ModuleInstance {
 
         let module_ref = ModuleInstance::alloc_module(loaded_module, extern_vals)?;
 
-		for element_segment in module.elements_section().map(|es| es.entries()).unwrap_or(
-			&[],
-		)
+        for element_segment in module
+            .elements_section()
+            .map(|es| es.entries())
+            .unwrap_or(&[])
         {
-			let offset_val = match eval_init_expr(element_segment.offset(), &module_ref) {
+            let offset = element_segment
+                .offset()
+                .as_ref()
+                .expect("passive segments are rejected due to validation");
+            let offset_val = match eval_init_expr(offset, &module_ref) {
                 RuntimeValue::I32(v) => v as u32,
                 _ => panic!("Due to validation elem segment offset should evaluate to i32"),
             };
 
-			let table_inst = module_ref.table_by_index(DEFAULT_TABLE_INDEX).expect(
-				"Due to validation default table should exists",
-			);
+            let table_inst = module_ref
+                .table_by_index(DEFAULT_TABLE_INDEX)
+                .expect("Due to validation default table should exists");
 
             // This check is not only for bailing out early, but also to check the case when
             // segment consist of 0 members.
-			if offset_val as u64 + element_segment.members().len() as u64 > table_inst.current_size() as u64 {
-				return Err(
-					Error::Instantiation("elements segment does not fit".to_string())
-				);
+            if offset_val as u64 + element_segment.members().len() as u64
+                > table_inst.current_size() as u64
+            {
+                return Err(Error::Instantiation(
+                    "elements segment does not fit".to_string(),
+                ));
             }
 
             for (j, func_idx) in element_segment.members().into_iter().enumerate() {
-				let func = module_ref.func_by_index(*func_idx).expect(
-					"Due to validation funcs from element segments should exists",
-				);
+                let func = module_ref
+                    .func_by_index(*func_idx)
+                    .expect("Due to validation funcs from element segments should exists");
 
                 table_inst.set(offset_val + j as u32, Some(func))?;
             }
         }
 
         for data_segment in module.data_section().map(|ds| ds.entries()).unwrap_or(&[]) {
-			let offset_val = match eval_init_expr(data_segment.offset(), &module_ref) {
+            let offset = data_segment
+                .offset()
+                .as_ref()
+                .expect("passive segments are rejected due to validation");
+            let offset_val = match eval_init_expr(offset, &module_ref) {
                 RuntimeValue::I32(v) => v as u32,
                 _ => panic!("Due to validation data segment offset should evaluate to i32"),
             };
 
-			let memory_inst = module_ref.memory_by_index(DEFAULT_MEMORY_INDEX).expect(
-				"Due to validation default memory should exists",
-			);
+            let memory_inst = module_ref
+                .memory_by_index(DEFAULT_MEMORY_INDEX)
+                .expect("Due to validation default memory should exists");
             memory_inst.set(offset_val, data_segment.value())?;
         }
 
@@ -534,17 +557,20 @@ impl ModuleInstance {
                 }
                 External::Table(ref table_type) => {
                     let table_descriptor = TableDescriptor::from_elements(table_type);
-					let table = imports.resolve_table(module_name, field_name, &table_descriptor)?;
+                    let table =
+                        imports.resolve_table(module_name, field_name, &table_descriptor)?;
                     ExternVal::Table(table)
                 }
                 External::Memory(ref memory_type) => {
                     let memory_descriptor = MemoryDescriptor::from_elements(memory_type);
-					let memory = imports.resolve_memory(module_name, field_name, &memory_descriptor)?;
+                    let memory =
+                        imports.resolve_memory(module_name, field_name, &memory_descriptor)?;
                     ExternVal::Memory(memory)
                 }
                 External::Global(ref global_type) => {
                     let global_descriptor = GlobalDescriptor::from_elements(global_type);
-					let global = imports.resolve_global(module_name, field_name, &global_descriptor)?;
+                    let global =
+                        imports.resolve_global(module_name, field_name, &global_descriptor)?;
                     ExternVal::Global(global)
                 }
             };
@@ -608,26 +634,45 @@ impl ModuleInstance {
         args: &[RuntimeValue],
         externals: &mut E,
     ) -> Result<Option<RuntimeValue>, Error> {
-		let extern_val = self.export_by_name(func_name).ok_or_else(|| {
-			Error::Function(format!("Module doesn't have export {}", func_name))
-		})?;
+        let func_instance = self.func_by_name(func_name)?;
 
-		let func_instance = match extern_val {
-			ExternVal::Func(func_instance) => func_instance,
-			unexpected => {
-				return Err(Error::Function(format!(
-					"Export {} is not a function, but {:?}",
-					func_name,
-					unexpected
-				)));
+        FuncInstance::invoke(&func_instance, args, externals).map_err(|t| Error::Trap(t))
     }
-		};
 
-		check_function_args(func_instance.signature(), &args)?;
-		FuncInstance::invoke(&func_instance, args, externals)
+    /// Invoke exported function by a name using recycled stacks.
+    ///
+    /// # Errors
+    ///
+    /// Same as [`invoke_export`].
+    ///
+    /// [`invoke_export`]: #method.invoke_export
+    pub fn invoke_export_with_stack<E: Externals>(
+        &self,
+        func_name: &str,
+        args: &[RuntimeValue],
+        externals: &mut E,
+        stack_recycler: &mut StackRecycler,
+    ) -> Result<Option<RuntimeValue>, Error> {
+        let func_instance = self.func_by_name(func_name)?;
+
+        FuncInstance::invoke_with_stack(&func_instance, args, externals, stack_recycler)
             .map_err(|t| Error::Trap(t))
     }
 
+    fn func_by_name(&self, func_name: &str) -> Result<FuncRef, Error> {
+        let extern_val = self
+            .export_by_name(func_name)
+            .ok_or_else(|| Error::Function(format!("Module doesn't have export {}", func_name)))?;
+
+        match extern_val {
+            ExternVal::Func(func_instance) => Ok(func_instance),
+            unexpected => Err(Error::Function(format!(
+                "Export {} is not a function, but {:?}",
+                func_name, unexpected
+            ))),
+        }
+    }
+
     /// Find export by a name.
     ///
     /// Returns `None` if there is no export with such name.
@@ -680,9 +725,10 @@ impl<'a> NotStartedModuleRef<'a> {
     /// Returns `Err` if start function traps.
     pub fn run_start<E: Externals>(self, state: &mut E) -> Result<ModuleRef, Trap> {
         if let Some(start_fn_idx) = self.loaded_module.module().start_section() {
-			let start_func = self.instance.func_by_index(start_fn_idx).expect(
-				"Due to validation start function should exists",
-			);
+            let start_func = self
+                .instance
+                .func_by_index(start_fn_idx)
+                .expect("Due to validation start function should exists");
             FuncInstance::invoke(&start_func, &[], state)?;
         }
         Ok(self.instance)
@@ -699,6 +745,13 @@ impl<'a> NotStartedModuleRef<'a> {
         }
         self.instance
     }
+
+    /// Whether or not the module has a `start` function.
+    ///
+    /// Returns `true` if it has a `start` function.
+    pub fn has_start(&self) -> bool {
+        self.loaded_module.module().start_section().is_some()
+    }
 }
 
 fn eval_init_expr(init_expr: &InitExpr, module: &ModuleInstance) -> RuntimeValue {
@@ -713,9 +766,9 @@ fn eval_init_expr(init_expr: &InitExpr, module: &ModuleInstance) -> RuntimeValue
         Instruction::F32Const(v) => RuntimeValue::decode_f32(v),
         Instruction::F64Const(v) => RuntimeValue::decode_f64(v),
         Instruction::GetGlobal(idx) => {
-			let global = module.global_by_index(idx).expect(
-				"Due to validation global should exists in module",
-			);
+            let global = module
+                .global_by_index(idx)
+                .expect("Due to validation global should exists in module");
             global.get()
         }
         _ => panic!("Due to validation init should be a const expr"),
@@ -739,7 +792,7 @@ fn match_limits(l1: &ResizableLimits, l2: &ResizableLimits) -> Result<(), Error>
                 "trying to import with limits l1.max={:?} and l2.max={:?}",
                 l1.maximum(),
                 l2.maximum()
-			)))
+            )));
         }
     }
 
@@ -760,14 +813,13 @@ pub fn check_limits(limits: &ResizableLimits) -> Result<(), Error> {
     Ok(())
 }
 
-
 #[cfg(test)]
 mod tests {
-	use imports::ImportsBuilder;
+    use super::{ExternVal, ModuleInstance};
     use func::FuncInstance;
-	use types::{Signature, ValueType};
-	use super::{ModuleInstance, ExternVal};
+    use imports::ImportsBuilder;
     use tests::parse_wat;
+    use types::{Signature, ValueType};
 
     #[should_panic]
     #[test]
@@ -777,12 +829,11 @@ mod tests {
 			(module
 				(func $f)
 				(start $f))
-			"#
+			"#,
         );
-		ModuleInstance::new(
-			&module_with_start,
-			&ImportsBuilder::default()
-		).unwrap().assert_no_start();
+        let module = ModuleInstance::new(&module_with_start, &ImportsBuilder::default()).unwrap();
+        assert!(!module.has_start());
+        module.assert_no_start();
     }
 
     #[test]
@@ -795,40 +846,39 @@ mod tests {
 			"#,
         );
 
-		assert!(
-			ModuleInstance::with_externvals(
+        assert!(ModuleInstance::with_externvals(
             &module_with_single_import,
-				[
-					ExternVal::Func(FuncInstance::alloc_host(Signature::new(&[][..], None), 0),)
-				].iter(),
-			).is_ok()
-		);
+            [ExternVal::Func(FuncInstance::alloc_host(
+                Signature::new(&[][..], None),
+                0
+            ),)]
+            .iter(),
+        )
+        .is_ok());
 
         // externval vector is longer than import count.
-		assert!(
-			ModuleInstance::with_externvals(
+        assert!(ModuleInstance::with_externvals(
             &module_with_single_import,
             [
                 ExternVal::Func(FuncInstance::alloc_host(Signature::new(&[][..], None), 0)),
                 ExternVal::Func(FuncInstance::alloc_host(Signature::new(&[][..], None), 1)),
-				].iter(),
-			).is_err()
-		);
+            ]
+            .iter(),
+        )
+        .is_err());
 
         // externval vector is shorter than import count.
         assert!(ModuleInstance::with_externvals(&module_with_single_import, [].iter(),).is_err());
 
         // externval vector has an unexpected type.
-		assert!(
-			ModuleInstance::with_externvals(
+        assert!(ModuleInstance::with_externvals(
             &module_with_single_import,
-				[
-					ExternVal::Func(FuncInstance::alloc_host(
+            [ExternVal::Func(FuncInstance::alloc_host(
                 Signature::new(&[][..], Some(ValueType::I32)),
                 0
-					),)
-				].iter(),
-			).is_err()
-		);
+            ),)]
+            .iter(),
+        )
+        .is_err());
     }
 }

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).
 ///
@@ -16,7 +16,7 @@ use module::check_limits;
 #[derive(Clone, Debug)]
 pub struct TableRef(Rc<TableInstance>);
 
-impl ::std::ops::Deref for TableRef {
+impl ::core::ops::Deref for TableRef {
     type Target = TableInstance;
     fn deref(&self) -> &TableInstance {
         &self.0
@@ -104,7 +104,9 @@ impl TableInstance {
     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)
+        let new_size = self
+            .current_size()
+            .checked_add(by)
             .and_then(|new_size| {
                 if maximum_size < new_size {
                     None
@@ -112,13 +114,13 @@ impl TableInstance {
                     Some(new_size)
                 }
             })
-			.ok_or_else(||
+            .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(())
     }
@@ -127,13 +129,12 @@ impl TableInstance {
     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(||
+        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
-			)),
-		)?;
+                offset, buffer_len
+            ))
+        })?;
         Ok(table_elem)
     }
 
@@ -141,13 +142,12 @@ impl TableInstance {
     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(||
+        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
+                offset, buffer_len
             ))
-		)?;
+        })?;
         *table_elem = value;
         Ok(())
     }

src/tests/host.rs

@@ -1,19 +1,19 @@
-use {
-	Error, Signature, Externals, FuncInstance, FuncRef, HostError, ImportsBuilder,
-	MemoryInstance, MemoryRef, TableInstance, TableRef, ModuleImportResolver, ModuleInstance, ModuleRef,
-	RuntimeValue, RuntimeArgs, TableDescriptor, MemoryDescriptor, Trap, TrapKind, ResumableError,
-};
-use types::ValueType;
-use memory_units::Pages;
 use super::parse_wat;
+use memory_units::Pages;
+use types::ValueType;
+use {
+    Error, Externals, FuncInstance, FuncRef, HostError, ImportsBuilder, MemoryDescriptor,
+    MemoryInstance, MemoryRef, ModuleImportResolver, ModuleInstance, ModuleRef, ResumableError,
+    RuntimeArgs, RuntimeValue, Signature, TableDescriptor, TableInstance, TableRef, Trap, TrapKind,
+};
 
 #[derive(Debug, Clone, PartialEq)]
 struct HostErrorWithCode {
     error_code: u32,
 }
 
-impl ::std::fmt::Display for HostErrorWithCode {
-	fn fmt(&self, f: &mut ::std::fmt::Formatter) -> Result<(), ::std::fmt::Error> {
+impl ::core::fmt::Display for HostErrorWithCode {
+    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> Result<(), ::core::fmt::Error> {
         write!(f, "{}", self.error_code)
     }
 }
@@ -107,9 +107,10 @@ impl Externals for TestHost {
             INC_MEM_FUNC_INDEX => {
                 let ptr: u32 = args.nth(0);
 
-				let memory = self.memory.as_ref().expect(
-					"Function 'inc_mem' expects attached memory",
-				);
+                let memory = self
+                    .memory
+                    .as_ref()
+                    .expect("Function 'inc_mem' expects attached memory");
                 let mut buf = [0u8; 1];
                 memory.get_into(ptr, &mut buf).unwrap();
                 buf[0] += 1;
@@ -120,18 +121,22 @@ impl Externals for TestHost {
             GET_MEM_FUNC_INDEX => {
                 let ptr: u32 = args.nth(0);
 
-				let memory = self.memory.as_ref().expect(
-					"Function 'get_mem' expects attached memory",
-				);
+                let memory = self
+                    .memory
+                    .as_ref()
+                    .expect("Function 'get_mem' expects attached memory");
                 let mut buf = [0u8; 1];
                 memory.get_into(ptr, &mut buf).unwrap();
 
                 Ok(Some(RuntimeValue::I32(buf[0] as i32)))
             }
             RECURSE_FUNC_INDEX => {
-				let val = args.nth_value_checked(0).expect("Exactly one argument expected");
+                let val = args
+                    .nth_value_checked(0)
+                    .expect("Exactly one argument expected");
 
-				let instance = self.instance
+                let instance = self
+                    .instance
                     .as_ref()
                     .expect("Function 'recurse' expects attached module instance")
                     .clone();
@@ -141,7 +146,9 @@ impl Externals for TestHost {
                     .expect("expected to be Some");
 
                 if val.value_type() != result.value_type() {
-					return Err(TrapKind::Host(Box::new(HostErrorWithCode { error_code: 123 })).into());
+                    return Err(
+                        TrapKind::Host(Box::new(HostErrorWithCode { error_code: 123 })).into(),
+                    );
                 }
                 Ok(Some(result))
             }
@@ -192,17 +199,17 @@ impl ModuleImportResolver for TestHost {
             "recurse" => RECURSE_FUNC_INDEX,
             "trap_sub" => TRAP_SUB_FUNC_INDEX,
             _ => {
-				return Err(Error::Instantiation(
-					format!("Export {} not found", field_name),
-				))
+                return Err(Error::Instantiation(format!(
+                    "Export {} not found",
+                    field_name
+                )));
             }
         };
 
         if !self.check_signature(index, signature) {
             return Err(Error::Instantiation(format!(
                 "Export `{}` doesnt match expected type {:?}",
-				field_name,
-				signature
+                field_name, signature
             )));
         }
 
@@ -214,9 +221,10 @@ impl ModuleImportResolver for TestHost {
         field_name: &str,
         _memory_type: &MemoryDescriptor,
     ) -> Result<MemoryRef, Error> {
-		Err(Error::Instantiation(
-			format!("Export {} not found", field_name),
-		))
+        Err(Error::Instantiation(format!(
+            "Export {} not found",
+            field_name
+        )))
     }
 }
 
@@ -244,9 +252,9 @@ fn call_host_func() {
         .assert_no_start();
 
     assert_eq!(
-		instance.invoke_export("test", &[], &mut env).expect(
-			"Failed to invoke 'test' function",
-		),
+        instance
+            .invoke_export("test", &[], &mut env)
+            .expect("Failed to invoke 'test' function",),
         Some(RuntimeValue::I32(-2))
     );
 }
@@ -277,23 +285,83 @@ fn resume_call_host_func() {
     let export = instance.export_by_name("test").unwrap();
     let func_instance = export.as_func().unwrap();
 
-	let mut invocation = FuncInstance::invoke_resumable(&func_instance, &[]).unwrap();
+    let mut invocation = FuncInstance::invoke_resumable(&func_instance, &[][..]).unwrap();
     let result = invocation.start_execution(&mut env);
     match result {
-		Err(ResumableError::Trap(_)) => {},
+        Err(ResumableError::Trap(_)) => {}
         _ => panic!(),
     }
 
     assert!(invocation.is_resumable());
     let trap_sub_result = env.trap_sub_result.take();
     assert_eq!(
-		invocation.resume_execution(trap_sub_result, &mut env).expect(
-			"Failed to invoke 'test' function",
-		),
+        invocation
+            .resume_execution(trap_sub_result, &mut env)
+            .expect("Failed to invoke 'test' function",),
         Some(RuntimeValue::I32(-2))
     );
 }
 
+#[test]
+fn resume_call_host_func_type_mismatch() {
+    fn resume_with_val(val: Option<RuntimeValue>) {
+        let module = parse_wat(
+            r#"
+            (module
+                (import "env" "trap_sub" (func $trap_sub (param i32 i32) (result i32)))
+
+                (func (export "test") (result i32)
+                    (call $trap_sub
+                        (i32.const 5)
+                        (i32.const 7)
+                    )
+                )
+            )
+            "#,
+        );
+
+        let mut env = TestHost::new();
+
+        let instance =
+            ModuleInstance::new(&module, &ImportsBuilder::new().with_resolver("env", &env))
+                .expect("Failed to instantiate module")
+                .assert_no_start();
+
+        let export = instance.export_by_name("test").unwrap();
+        let func_instance = export.as_func().unwrap();
+
+        let mut invocation = FuncInstance::invoke_resumable(&func_instance, &[][..]).unwrap();
+        let result = invocation.start_execution(&mut env);
+        match result {
+            Err(ResumableError::Trap(_)) => {}
+            _ => panic!(),
+        }
+
+        assert!(invocation.is_resumable());
+        let err = invocation.resume_execution(val, &mut env).unwrap_err();
+
+        match &err {
+            ResumableError::Trap(trap) => {
+                if let TrapKind::UnexpectedSignature = trap.kind() {
+                    return;
+                }
+            }
+            _ => {}
+        }
+
+        // If didn't return in the previous `match`...
+
+        panic!(
+            "Expected `ResumableError::Trap(Trap {{ kind: \
+             TrapKind::UnexpectedSignature, }})`, got `{:?}`",
+            err
+        )
+    }
+
+    resume_with_val(None);
+    resume_with_val(Some((-1i64).into()));
+}
+
 #[test]
 fn host_err() {
     let module = parse_wat(
@@ -316,13 +384,15 @@ fn host_err() {
         .expect("Failed to instantiate module")
         .assert_no_start();
 
-	let error = instance.invoke_export("test", &[], &mut env).expect_err(
-		"`test` expected to return error",
-	);
+    let error = instance
+        .invoke_export("test", &[], &mut env)
+        .expect_err("`test` expected to return error");
 
-	let error_with_code = error.as_host_error().expect("Expected host error").downcast_ref::<HostErrorWithCode>().expect(
-		"Failed to downcast to expected error type",
-	);
+    let error_with_code = error
+        .as_host_error()
+        .expect("Expected host error")
+        .downcast_ref::<HostErrorWithCode>()
+        .expect("Failed to downcast to expected error type");
     assert_eq!(error_with_code.error_code, 228);
 }
 
@@ -351,9 +421,9 @@ fn modify_mem_with_host_funcs() {
         .expect("Failed to instantiate module")
         .assert_no_start();
 
-	instance.invoke_export("modify_mem", &[], &mut env).expect(
-		"Failed to invoke 'test' function",
-	);
+    instance
+        .invoke_export("modify_mem", &[], &mut env)
+        .expect("Failed to invoke 'test' function");
 
     // Check contents of memory at address 12.
     let mut buf = [0u8; 1];
@@ -451,9 +521,9 @@ fn recursion() {
     env.instance = Some(instance.clone());
 
     assert_eq!(
-		instance.invoke_export("test", &[], &mut env).expect(
-			"Failed to invoke 'test' function",
-		),
+        instance
+            .invoke_export("test", &[], &mut env)
+            .expect("Failed to invoke 'test' function",),
         // 363 = 321 + 42
         Some(RuntimeValue::I64(363))
     );
@@ -472,21 +542,17 @@ fn defer_providing_externals() {
     }
 
     impl ModuleImportResolver for HostImportResolver {
-		fn resolve_func(
-			&self,
-			field_name: &str,
-			signature: &Signature,
-		) -> Result<FuncRef, Error> {
+        fn resolve_func(&self, field_name: &str, signature: &Signature) -> Result<FuncRef, Error> {
             if field_name != "inc" {
-				return Err(Error::Instantiation(
-					format!("Export {} not found", field_name),
-				));
+                return Err(Error::Instantiation(format!(
+                    "Export {} not found",
+                    field_name
+                )));
             }
             if signature.params() != &[ValueType::I32] || signature.return_type() != None {
                 return Err(Error::Instantiation(format!(
                     "Export `{}` doesnt match expected type {:?}",
-					field_name,
-					signature
+                    field_name, signature
                 )));
             }
 
@@ -501,9 +567,10 @@ fn defer_providing_externals() {
             if field_name == "mem" {
                 Ok(self.mem.clone())
             } else {
-				Err(Error::Instantiation(
-					format!("Export {} not found", field_name),
-				))
+                Err(Error::Instantiation(format!(
+                    "Export {} not found",
+                    field_name
+                )))
             }
         }
     }
@@ -547,14 +614,16 @@ fn defer_providing_externals() {
 
     // Create HostImportResolver with some initialized memory instance.
     // This memory instance will be provided as 'mem' export.
-	let host_import_resolver =
-		HostImportResolver { mem: MemoryInstance::alloc(Pages(1), Some(Pages(1))).unwrap() };
+    let host_import_resolver = HostImportResolver {
+        mem: MemoryInstance::alloc(Pages(1), Some(Pages(1))).unwrap(),
+    };
 
     // Instantiate module with `host_import_resolver` as import resolver for "host" module.
     let instance = ModuleInstance::new(
         &module,
         &ImportsBuilder::new().with_resolver("host", &host_import_resolver),
-	).expect("Failed to instantiate module")
+    )
+    .expect("Failed to instantiate module")
     .assert_no_start();
 
     let mut acc = 89;
@@ -599,18 +668,15 @@ fn two_envs_one_externals() {
     struct OrdinaryResolver;
 
     impl ModuleImportResolver for PrivilegedResolver {
-		fn resolve_func(
-			&self,
-			field_name: &str,
-			signature: &Signature,
-		) -> Result<FuncRef, Error> {
+        fn resolve_func(&self, field_name: &str, signature: &Signature) -> Result<FuncRef, Error> {
             let index = match field_name {
                 "ordinary" => ORDINARY_FUNC_INDEX,
                 "privileged" => PRIVILEGED_FUNC_INDEX,
                 _ => {
-					return Err(Error::Instantiation(
-						format!("Export {} not found", field_name),
-					))
+                    return Err(Error::Instantiation(format!(
+                        "Export {} not found",
+                        field_name
+                    )));
                 }
             };
 
@@ -619,22 +685,19 @@ fn two_envs_one_externals() {
     }
 
     impl ModuleImportResolver for OrdinaryResolver {
-		fn resolve_func(
-			&self,
-			field_name: &str,
-			signature: &Signature,
-		) -> Result<FuncRef, Error> {
+        fn resolve_func(&self, field_name: &str, signature: &Signature) -> Result<FuncRef, Error> {
             let index = match field_name {
                 "ordinary" => ORDINARY_FUNC_INDEX,
                 "privileged" => {
                     return Err(Error::Instantiation(
                         "'priveleged' can be imported only in privileged context".into(),
-					))
+                    ));
                 }
                 _ => {
-					return Err(Error::Instantiation(
-						format!("Export {} not found", field_name),
-					))
+                    return Err(Error::Instantiation(format!(
+                        "Export {} not found",
+                        field_name
+                    )));
                 }
             };
 
@@ -673,7 +736,8 @@ fn two_envs_one_externals() {
     let trusted_instance = ModuleInstance::new(
         &trusted_module,
         &ImportsBuilder::new().with_resolver("env", &PrivilegedResolver),
-	).expect("Failed to instantiate module")
+    )
+    .expect("Failed to instantiate module")
     .assert_no_start();
 
     let untrusted_instance = ModuleInstance::new(
@@ -681,7 +745,8 @@ fn two_envs_one_externals() {
         &ImportsBuilder::new()
             .with_resolver("env", &OrdinaryResolver)
             .with_resolver("trusted", &trusted_instance),
-	).expect("Failed to instantiate module")
+    )
+    .expect("Failed to instantiate module")
     .assert_no_start();
 
     untrusted_instance
@@ -716,7 +781,8 @@ fn dynamically_add_host_func() {
                         Signature::new(&[][..], Some(ValueType::I32)),
                         host_func_index as usize,
                     );
-					self.table.set(table_index, Some(added_func))
+                    self.table
+                        .set(table_index, Some(added_func))
                         .map_err(|_| TrapKind::TableAccessOutOfBounds)?;
 
                     Ok(Some(RuntimeValue::I32(table_index as i32)))
@@ -730,17 +796,14 @@ fn dynamically_add_host_func() {
     }
 
     impl ModuleImportResolver for HostExternals {
-		fn resolve_func(
-			&self,
-			field_name: &str,
-			signature: &Signature,
-		) -> Result<FuncRef, Error> {
+        fn resolve_func(&self, field_name: &str, signature: &Signature) -> Result<FuncRef, Error> {
             let index = match field_name {
                 "add_func" => ADD_FUNC_FUNC_INDEX,
                 _ => {
-					return Err(Error::Instantiation(
-						format!("Export {} not found", field_name),
-					))
+                    return Err(Error::Instantiation(format!(
+                        "Export {} not found",
+                        field_name
+                    )));
                 }
             };
             Ok(FuncInstance::alloc_host(signature.clone(), index))
@@ -754,9 +817,10 @@ fn dynamically_add_host_func() {
             if field_name == "table" {
                 Ok(self.table.clone())
             } else {
-				Err(Error::Instantiation(
-					format!("Export {} not found", field_name),
-				))
+                Err(Error::Instantiation(format!(
+                    "Export {} not found",
+                    field_name
+                )))
             }
         }
     }
@@ -788,7 +852,8 @@ fn dynamically_add_host_func() {
     let instance = ModuleInstance::new(
         &module,
         &ImportsBuilder::new().with_resolver("env", &host_externals),
-	).expect("Failed to instantiate module")
+    )
+    .expect("Failed to instantiate module")
     .assert_no_start();
 
     assert_eq!(

src/tests/mod.rs

@@ -1,5 +1,5 @@
 use wabt;
-use {Module};
+use Module;
 
 mod host;
 mod wasm;
@@ -23,11 +23,17 @@ fn assert_error_properties() {
 fn unsigned_to_runtime_value() {
     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 {

src/tests/wasm.rs

@@ -1,10 +1,10 @@
-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,
@@ -60,12 +60,17 @@ impl ModuleImportResolver for Env {
         }
     }
 
-	fn resolve_table(&self, field_name: &str, _table_type: &TableDescriptor) -> Result<TableRef, Error> {
+    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),
-			)),
+            _ => Err(Error::Instantiation(format!(
+                "env module doesn't provide table '{}'",
+                field_name
+            ))),
         }
     }
 }
@@ -90,10 +95,8 @@ fn interpreter_inc_i32() {
 
     let env = Env::new();
 
-	let instance = ModuleInstance::new(
-		&module,
-		&ImportsBuilder::new().with_resolver("env", &env),
-	).expect("Failed to instantiate module")
+    let instance = ModuleInstance::new(&module, &ImportsBuilder::new().with_resolver("env", &env))
+        .expect("Failed to instantiate module")
         .assert_no_start();
 
     let i32_val = 42;
@@ -114,17 +117,14 @@ 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 env = Env::new();
-	let instance = ModuleInstance::new(
-		&module,
-		&ImportsBuilder::new().with_resolver("env", &env),
-	).expect("Failed to instantiate module")
+    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].
 ///
@@ -38,7 +39,7 @@ impl Signature {
     /// ```
     pub fn new<C: Into<Cow<'static, [ValueType]>>>(
         params: C,
-		return_type: Option<ValueType>
+        return_type: Option<ValueType>,
     ) -> Signature {
         Signature {
             params: params.into(),
@@ -58,7 +59,12 @@ impl Signature {
 
     pub(crate) fn from_elements(func_type: &FunctionType) -> Signature {
         Signature {
-			params: func_type.params().iter().cloned().map(ValueType::from_elements).collect(),
+            params: func_type
+                .params()
+                .iter()
+                .cloned()
+                .map(ValueType::from_elements)
+                .collect(),
             return_type: func_type.return_type().map(ValueType::from_elements),
         }
     }

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/mod.rs

@@ -1,452 +0,0 @@
-use std::error;
-use std::fmt;
-use std::collections::HashSet;
-use parity_wasm::elements::{
-	BlockType, External, GlobalEntry, GlobalType, Internal, MemoryType, Module, Instruction,
-	ResizableLimits, TableType, ValueType, InitExpr, Type,
-};
-use common::stack;
-use self::context::ModuleContextBuilder;
-use self::func::FunctionReader;
-use memory_units::Pages;
-use isa;
-
-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 code_map: Vec<isa::Instructions>,
-	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::Instruction::*;
-
-			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()) {
-		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 code_map = Vec::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 code = FunctionReader::read_function(&context, function, function_body)
-				.map_err(|e| {
-					let Error(ref msg) = e;
-					Error(format!("Function #{} reading/validation error: {}", index, msg))
-				})?;
-			code_map.push(code);
-		}
-	}
-
-	// 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,
-		code_map,
-	})
-}
-
-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] {
-		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)
-}

src/validation/tests.rs

@@ -1,932 +0,0 @@
-use super::{validate_module, ValidatedModule};
-use parity_wasm::builder::module;
-use parity_wasm::elements::{
-	External, GlobalEntry, GlobalType, ImportEntry, InitExpr, MemoryType,
-	Instruction, Instructions, TableType, ValueType, BlockType, deserialize_buffer,
-	Module,
-};
-use isa;
-use wabt;
-
-#[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();
-}
-
-fn validate(wat: &str) -> ValidatedModule {
-	let wasm = wabt::wat2wasm(wat).unwrap();
-	let module = deserialize_buffer::<Module>(&wasm).unwrap();
-	let validated_module = validate_module(module).unwrap();
-	validated_module
-}
-
-fn compile(wat: &str) -> (Vec<isa::Instruction>, Vec<u32>) {
-	let validated_module = validate(wat);
-	let code = &validated_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)
-}
-
-#[test]
-fn implicit_return_no_value() {
-	let (code, _) = compile(r#"
-		(module
-			(func (export "call")
-			)
-		)
-	"#);
-	assert_eq!(
-		code,
-		vec![
-			isa::Instruction::Return(isa::DropKeep {
-				drop: 0,
-				keep: isa::Keep::None,
-			})
-		]
-	)
-}
-
-#[test]
-fn implicit_return_with_value() {
-	let (code, _) = compile(r#"
-		(module
-			(func (export "call") (result i32)
-				i32.const 0
-			)
-		)
-	"#);
-	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 (code, _) = compile(r#"
-		(module
-			(func (export "call") (param i32)
-			)
-		)
-	"#);
-	assert_eq!(
-		code,
-		vec![
-			isa::Instruction::Return(isa::DropKeep {
-				drop: 1,
-				keep: isa::Keep::None,
-			}),
-		]
-	)
-}
-
-#[test]
-fn get_local() {
-	let (code, _) = compile(r#"
-		(module
-			(func (export "call") (param i32) (result i32)
-				get_local 0
-			)
-		)
-	"#);
-	assert_eq!(
-		code,
-		vec![
-			isa::Instruction::GetLocal(1),
-			isa::Instruction::Return(isa::DropKeep {
-				drop: 1,
-				keep: isa::Keep::Single,
-			}),
-		]
-	)
-}
-
-#[test]
-fn explicit_return() {
-	let (code, _) = compile(r#"
-		(module
-			(func (export "call") (param i32) (result i32)
-				get_local 0
-				return
-			)
-		)
-	"#);
-	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 (code, _) = compile(r#"
-		(module
-			(func (export "call") (param i32) (param i32) (result i32)
-				get_local 0
-				get_local 1
-				i32.add
-			)
-		)
-	"#);
-	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 (code, _) = compile(r#"
-		(module
-			(func (export "call") (param i32)
-				(local i32)
-				get_local 0
-				set_local 1
-			)
-		)
-	"#);
-	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 (code, pcs) = compile(r#"
-		(module
-			(func (export "call") (param i32) (result i32)
-				i32.const 1
-				if
-					i32.const 2
-					return
-				end
-				i32.const 3
-			)
-		)
-	"#);
-	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 (code, pcs) = compile(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
-			)
-		)
-	"#);
-	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 (code, pcs) = compile(r#"
-		(module
-			(func (export "call")
-				i32.const 1
-				if (result i32)
-					i32.const 2
-				else
-					i32.const 3
-				end
-				drop
-			)
-		)
-	"#);
-	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 (code, pcs) = compile(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
-			)
-		)
-	"#);
-	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 (code, pcs) = compile(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
-			)
-		)
-	"#);
-	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 (code, _) = compile(r#"
-		(module
-			(func (export "call")
-				loop (result i32)
-					i32.const 1
-					br_if 0
-					i32.const 2
-				end
-				drop
-			)
-		)
-	"#);
-	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 (code, _) = compile(r#"
-		(module
-			(func (export "call")
-				loop
-				end
-			)
-		)
-	"#);
-	assert_eq!(
-		code,
-		vec![
-			isa::Instruction::Return(isa::DropKeep {
-				drop: 0,
-				keep: isa::Keep::None,
-			}),
-		]
-	)
-}
-
-#[test]
-fn brtable() {
-	let (code, pcs) = compile(r#"
-		(module
-			(func (export "call")
-				block $1
-					loop $2
-						i32.const 0
-						br_table $2 $1
-					end
-				end
-			)
-		)
-	"#);
-	assert_eq!(
-		code,
-		vec![
-			isa::Instruction::I32Const(0),
-			isa::Instruction::BrTable(
-				vec![
-					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,
-						},
-					},
-				].into_boxed_slice()
-			),
-			isa::Instruction::Return(isa::DropKeep {
-				drop: 0,
-				keep: isa::Keep::None,
-			}),
-		]
-	)
-}
-
-#[test]
-fn brtable_returns_result() {
-	let (code, pcs) = compile(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
-			)
-		)
-	"#);
-	assert_eq!(
-		code,
-		vec![
-			isa::Instruction::I32Const(0),
-			isa::Instruction::I32Const(1),
-			isa::Instruction::BrTable(
-				vec![
-					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,
-						},
-					},
-				].into_boxed_slice()
-			),
-			isa::Instruction::Unreachable,
-			isa::Instruction::Drop,
-			isa::Instruction::Return(isa::DropKeep {
-				drop: 0,
-				keep: isa::Keep::None,
-			}),
-		]
-	)
-}
-
-#[test]
-fn wabt_example() {
-	let (code, pcs) = compile(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
-			)
-		)
-	"#);
-	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/validation/util.rs

@@ -1,131 +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],
-	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(_)
-		);
-	}
-}

src/value.rs

@@ -1,12 +1,12 @@
-use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt};
+use core::{f32, i32, i64, u32, u64};
 use nan_preserving_float::{F32, F64};
-use std::io;
-use std::mem::transmute;
-use std::{f32, i32, i64, u32, u64};
+use types::ValueType;
 use TrapKind;
 
+/// Error for `LittleEndianConvert`
 #[derive(Debug)]
 pub enum Error {
+    /// The buffer is too short for the type being deserialized
     InvalidLittleEndianBuffer,
 }
 
@@ -38,7 +38,10 @@ pub enum RuntimeValue {
 /// [`I32`]: enum.RuntimeValue.html#variant.I32
 /// [`F64`]: enum.RuntimeValue.html#variant.F64
 /// [`RuntimeValue`]: enum.RuntimeValue.html
-pub trait FromRuntimeValue where Self: Sized {
+pub trait FromRuntimeValue
+where
+    Self: Sized,
+{
     /// Create a value of type `Self` from a given [`RuntimeValue`].
     ///
     /// Returns `None` if the [`RuntimeValue`] is of type different than
@@ -73,9 +76,12 @@ pub trait TransmuteInto<T> {
 }
 
 /// Convert from and to little endian.
-pub trait LittleEndianConvert where Self: Sized {
+pub trait LittleEndianConvert
+where
+    Self: Sized,
+{
     /// Convert to little endian buffer.
-	fn into_little_endian(self, buffer: &mut[u8]);
+    fn into_little_endian(self, buffer: &mut [u8]);
     /// Convert from little endian buffer.
     fn from_little_endian(buffer: &[u8]) -> Result<Self, Error>;
 }
@@ -134,12 +140,12 @@ pub trait Float<T>: ArithmeticOps<T> {
 
 impl RuntimeValue {
     /// Creates new default value of given type.
-	pub fn default(value_type: ::types::ValueType) -> Self {
+    pub fn default(value_type: ValueType) -> Self {
         match value_type {
-			::types::ValueType::I32 => RuntimeValue::I32(0),
-			::types::ValueType::I64 => RuntimeValue::I64(0),
-			::types::ValueType::F32 => RuntimeValue::F32(0f32.into()),
-			::types::ValueType::F64 => RuntimeValue::F64(0f64.into()),
+            ValueType::I32 => RuntimeValue::I32(0),
+            ValueType::I64 => RuntimeValue::I64(0),
+            ValueType::F32 => RuntimeValue::F32(0f32.into()),
+            ValueType::F64 => RuntimeValue::F64(0f64.into()),
         }
     }
 
@@ -154,12 +160,12 @@ impl RuntimeValue {
     }
 
     /// Get variable type for this value.
-	pub fn value_type(&self) -> ::types::ValueType {
+    pub fn value_type(&self) -> ValueType {
         match *self {
-			RuntimeValue::I32(_) => ::types::ValueType::I32,
-			RuntimeValue::I64(_) => ::types::ValueType::I64,
-			RuntimeValue::F32(_) => ::types::ValueType::F32,
-			RuntimeValue::F64(_) => ::types::ValueType::F64,
+            RuntimeValue::I32(_) => ValueType::I32,
+            RuntimeValue::I64(_) => ValueType::I64,
+            RuntimeValue::F32(_) => ValueType::F32,
+            RuntimeValue::F64(_) => ValueType::F64,
         }
     }
 
@@ -360,8 +366,17 @@ impl WrapInto<F32> for F64 {
 }
 
 macro_rules! impl_try_truncate_into {
-	($from: ident, $into: ident) => {
+    (@primitive $from: ident, $into: ident, $to_primitive:path) => {
         impl TryTruncateInto<$into, TrapKind> for $from {
+            #[cfg(feature = "std")]
+            fn try_truncate_into(self) -> Result<$into, TrapKind> {
+                // Casting from a float to an integer will round the float towards zero
+                num_rational::BigRational::from_float(self)
+                    .map(|val| val.to_integer())
+                    .and_then(|val| $to_primitive(&val))
+                    .ok_or(TrapKind::InvalidConversionToInt)
+            }
+            #[cfg(not(feature = "std"))]
             fn try_truncate_into(self) -> Result<$into, TrapKind> {
                 // Casting from a float to an integer will round the float towards zero
                 // NOTE: currently this will cause Undefined Behavior if the rounded value cannot be represented by the
@@ -380,7 +395,7 @@ macro_rules! impl_try_truncate_into {
             }
         }
     };
-	($from:ident, $intermediate:ident, $into:ident) => {
+    (@wrapped $from:ident, $intermediate:ident, $into:ident) => {
         impl TryTruncateInto<$into, TrapKind> for $from {
             fn try_truncate_into(self) -> Result<$into, TrapKind> {
                 $intermediate::from(self).try_truncate_into()
@@ -389,22 +404,22 @@ macro_rules! impl_try_truncate_into {
     };
 }
 
-impl_try_truncate_into!(f32, i32);
-impl_try_truncate_into!(f32, i64);
-impl_try_truncate_into!(f64, i32);
-impl_try_truncate_into!(f64, i64);
-impl_try_truncate_into!(f32, u32);
-impl_try_truncate_into!(f32, u64);
-impl_try_truncate_into!(f64, u32);
-impl_try_truncate_into!(f64, u64);
-impl_try_truncate_into!(F32, f32, i32);
-impl_try_truncate_into!(F32, f32, i64);
-impl_try_truncate_into!(F64, f64, i32);
-impl_try_truncate_into!(F64, f64, i64);
-impl_try_truncate_into!(F32, f32, u32);
-impl_try_truncate_into!(F32, f32, u64);
-impl_try_truncate_into!(F64, f64, u32);
-impl_try_truncate_into!(F64, f64, u64);
+impl_try_truncate_into!(@primitive f32, i32, num_traits::cast::ToPrimitive::to_i32);
+impl_try_truncate_into!(@primitive f32, i64, num_traits::cast::ToPrimitive::to_i64);
+impl_try_truncate_into!(@primitive f64, i32, num_traits::cast::ToPrimitive::to_i32);
+impl_try_truncate_into!(@primitive f64, i64, num_traits::cast::ToPrimitive::to_i64);
+impl_try_truncate_into!(@primitive f32, u32, num_traits::cast::ToPrimitive::to_u32);
+impl_try_truncate_into!(@primitive f32, u64, num_traits::cast::ToPrimitive::to_u64);
+impl_try_truncate_into!(@primitive f64, u32, num_traits::cast::ToPrimitive::to_u32);
+impl_try_truncate_into!(@primitive f64, u64, num_traits::cast::ToPrimitive::to_u64);
+impl_try_truncate_into!(@wrapped F32, f32, i32);
+impl_try_truncate_into!(@wrapped F32, f32, i64);
+impl_try_truncate_into!(@wrapped F64, f64, i32);
+impl_try_truncate_into!(@wrapped F64, f64, i64);
+impl_try_truncate_into!(@wrapped F32, f32, u32);
+impl_try_truncate_into!(@wrapped F32, f32, u64);
+impl_try_truncate_into!(@wrapped F64, f64, u32);
+impl_try_truncate_into!(@wrapped F64, f64, u64);
 
 macro_rules! impl_extend_into {
     ($from:ident, $into:ident) => {
@@ -463,7 +478,7 @@ macro_rules! impl_transmute_into_self {
                 self
             }
         }
-	}
+    };
 }
 
 impl_transmute_into_self!(i32);
@@ -480,7 +495,7 @@ macro_rules! impl_transmute_into_as {
                 self as $into
             }
         }
-	}
+    };
 }
 
 impl_transmute_into_as!(i8, u8);
@@ -531,141 +546,188 @@ impl_transmute_into_npf!(F32, f32, i32, u32);
 impl_transmute_into_npf!(F64, f64, i64, u64);
 
 impl TransmuteInto<i32> for f32 {
-	fn transmute_into(self) -> i32 { self.to_bits() as i32 }
+    fn transmute_into(self) -> i32 {
+        self.to_bits() as i32
+    }
 }
 
 impl TransmuteInto<i64> for f64 {
-	fn transmute_into(self) -> i64 { self.to_bits() as i64 }
+    fn transmute_into(self) -> i64 {
+        self.to_bits() as i64
+    }
 }
 
 impl TransmuteInto<f32> for i32 {
-	fn transmute_into(self) -> f32 { f32::from_bits(self as u32) }
+    fn transmute_into(self) -> f32 {
+        f32::from_bits(self as u32)
+    }
 }
 
 impl TransmuteInto<f64> for i64 {
-	fn transmute_into(self) -> f64 { f64::from_bits(self as u64) }
+    fn transmute_into(self) -> f64 {
+        f64::from_bits(self as u64)
+    }
 }
 
 impl TransmuteInto<i32> for u32 {
-	fn transmute_into(self) -> i32 { unsafe { transmute(self) } }
+    fn transmute_into(self) -> i32 {
+        self as _
+    }
 }
 
 impl TransmuteInto<i64> for u64 {
-	fn transmute_into(self) -> i64 { unsafe { transmute(self) } }
+    fn transmute_into(self) -> i64 {
+        self as _
+    }
 }
 
 impl LittleEndianConvert for i8 {
-	fn into_little_endian(self, buffer: &mut[u8]) {
+    fn into_little_endian(self, buffer: &mut [u8]) {
         buffer[0] = self as u8;
     }
 
     fn from_little_endian(buffer: &[u8]) -> Result<Self, Error> {
-		buffer.get(0)
+        buffer
+            .get(0)
             .map(|v| *v as i8)
             .ok_or_else(|| Error::InvalidLittleEndianBuffer)
     }
 }
 
 impl LittleEndianConvert for u8 {
-	fn into_little_endian(self, buffer: &mut[u8]) {
+    fn into_little_endian(self, buffer: &mut [u8]) {
         buffer[0] = self;
     }
 
     fn from_little_endian(buffer: &[u8]) -> Result<Self, Error> {
-		buffer.get(0)
+        buffer
+            .get(0)
             .cloned()
             .ok_or_else(|| Error::InvalidLittleEndianBuffer)
     }
 }
 
 impl LittleEndianConvert for i16 {
-	fn into_little_endian(self, mut buffer: &mut[u8]) {
-		buffer.write_i16::<LittleEndian>(self)
-			.expect("i16 is written without any errors");
+    fn into_little_endian(self, buffer: &mut [u8]) {
+        buffer.copy_from_slice(&self.to_le_bytes());
     }
 
     fn from_little_endian(buffer: &[u8]) -> Result<Self, Error> {
-		io::Cursor::new(buffer).read_i16::<LittleEndian>()
-			.map_err(|_| Error::InvalidLittleEndianBuffer)
+        let mut res = [0u8; 2];
+        buffer
+            .get(0..2)
+            .map(|s| {
+                res.copy_from_slice(s);
+                Self::from_le_bytes(res)
+            })
+            .ok_or_else(|| Error::InvalidLittleEndianBuffer)
     }
 }
 
 impl LittleEndianConvert for u16 {
-	fn into_little_endian(self, mut buffer: &mut[u8]) {
-		buffer.write_u16::<LittleEndian>(self)
-			.expect("u16 is written without any errors");
+    fn into_little_endian(self, buffer: &mut [u8]) {
+        buffer.copy_from_slice(&self.to_le_bytes());
     }
 
     fn from_little_endian(buffer: &[u8]) -> Result<Self, Error> {
-		io::Cursor::new(buffer).read_u16::<LittleEndian>()
-			.map_err(|_| Error::InvalidLittleEndianBuffer)
+        let mut res = [0u8; 2];
+        buffer
+            .get(0..2)
+            .map(|s| {
+                res.copy_from_slice(s);
+                Self::from_le_bytes(res)
+            })
+            .ok_or_else(|| Error::InvalidLittleEndianBuffer)
     }
 }
 
 impl LittleEndianConvert for i32 {
-	fn into_little_endian(self, mut buffer: &mut[u8]) {
-		buffer.write_i32::<LittleEndian>(self)
-			.expect("i32 is written without any errors");
+    fn into_little_endian(self, buffer: &mut [u8]) {
+        buffer.copy_from_slice(&self.to_le_bytes());
     }
 
     fn from_little_endian(buffer: &[u8]) -> Result<Self, Error> {
-		io::Cursor::new(buffer).read_i32::<LittleEndian>()
-			.map_err(|_| Error::InvalidLittleEndianBuffer)
+        let mut res = [0u8; 4];
+        buffer
+            .get(0..4)
+            .map(|s| {
+                res.copy_from_slice(s);
+                Self::from_le_bytes(res)
+            })
+            .ok_or_else(|| Error::InvalidLittleEndianBuffer)
     }
 }
 
 impl LittleEndianConvert for u32 {
-	fn into_little_endian(self, mut buffer: &mut[u8]) {
-		buffer.write_u32::<LittleEndian>(self)
-			.expect("u32 is written without any errors");
+    fn into_little_endian(self, buffer: &mut [u8]) {
+        buffer.copy_from_slice(&self.to_le_bytes());
     }
 
     fn from_little_endian(buffer: &[u8]) -> Result<Self, Error> {
-		io::Cursor::new(buffer).read_u32::<LittleEndian>()
-			.map_err(|_| Error::InvalidLittleEndianBuffer)
+        let mut res = [0u8; 4];
+        buffer
+            .get(0..4)
+            .map(|s| {
+                res.copy_from_slice(s);
+                Self::from_le_bytes(res)
+            })
+            .ok_or_else(|| Error::InvalidLittleEndianBuffer)
     }
 }
 
 impl LittleEndianConvert for i64 {
-	fn into_little_endian(self, mut buffer: &mut[u8]) {
-		buffer.write_i64::<LittleEndian>(self)
-			.expect("i64 is written without any errors");
+    fn into_little_endian(self, buffer: &mut [u8]) {
+        buffer.copy_from_slice(&self.to_le_bytes());
     }
 
     fn from_little_endian(buffer: &[u8]) -> Result<Self, Error> {
-		io::Cursor::new(buffer).read_i64::<LittleEndian>()
-			.map_err(|_| Error::InvalidLittleEndianBuffer)
+        let mut res = [0u8; 8];
+        buffer
+            .get(0..8)
+            .map(|s| {
+                res.copy_from_slice(s);
+                Self::from_le_bytes(res)
+            })
+            .ok_or_else(|| Error::InvalidLittleEndianBuffer)
     }
 }
 
 impl LittleEndianConvert for f32 {
-	fn into_little_endian(self, mut buffer: &mut[u8]) {
-		buffer.write_f32::<LittleEndian>(self)
-			.expect("f32 is written without any errors");
+    fn into_little_endian(self, buffer: &mut [u8]) {
+        buffer.copy_from_slice(&self.to_bits().to_le_bytes());
     }
 
     fn from_little_endian(buffer: &[u8]) -> Result<Self, Error> {
-		io::Cursor::new(buffer).read_u32::<LittleEndian>()
-			.map(f32::from_bits)
-			.map_err(|_| Error::InvalidLittleEndianBuffer)
+        let mut res = [0u8; 4];
+        buffer
+            .get(0..4)
+            .map(|s| {
+                res.copy_from_slice(s);
+                Self::from_bits(u32::from_le_bytes(res))
+            })
+            .ok_or_else(|| Error::InvalidLittleEndianBuffer)
     }
 }
 
 impl LittleEndianConvert for f64 {
-	fn into_little_endian(self, mut buffer: &mut[u8]) {
-		buffer.write_f64::<LittleEndian>(self)
-			.expect("i64 is written without any errors");
+    fn into_little_endian(self, buffer: &mut [u8]) {
+        buffer.copy_from_slice(&self.to_bits().to_le_bytes());
     }
 
     fn from_little_endian(buffer: &[u8]) -> Result<Self, Error> {
-		io::Cursor::new(buffer).read_u64::<LittleEndian>()
-			.map(f64::from_bits)
-			.map_err(|_| Error::InvalidLittleEndianBuffer)
+        let mut res = [0u8; 8];
+        buffer
+            .get(0..8)
+            .map(|s| {
+                res.copy_from_slice(s);
+                Self::from_bits(u64::from_le_bytes(res))
+            })
+            .ok_or_else(|| Error::InvalidLittleEndianBuffer)
     }
 }
 
 impl LittleEndianConvert for F32 {
-	fn into_little_endian(self, buffer: &mut[u8]) {
+    fn into_little_endian(self, buffer: &mut [u8]) {
         (self.to_bits() as i32).into_little_endian(buffer)
     }
 
@@ -675,7 +737,7 @@ impl LittleEndianConvert for F32 {
 }
 
 impl LittleEndianConvert for F64 {
-	fn into_little_endian(self, buffer: &mut[u8]) {
+    fn into_little_endian(self, buffer: &mut [u8]) {
         (self.to_bits() as i64).into_little_endian(buffer)
     }
 
@@ -687,14 +749,19 @@ impl LittleEndianConvert for F64 {
 macro_rules! impl_integer_arithmetic_ops {
     ($type: ident) => {
         impl ArithmeticOps<$type> for $type {
-			fn add(self, other: $type) -> $type { self.wrapping_add(other) }
-			fn sub(self, other: $type) -> $type { self.wrapping_sub(other) }
-			fn mul(self, other: $type) -> $type { self.wrapping_mul(other) }
+            fn add(self, other: $type) -> $type {
+                self.wrapping_add(other)
+            }
+            fn sub(self, other: $type) -> $type {
+                self.wrapping_sub(other)
+            }
+            fn mul(self, other: $type) -> $type {
+                self.wrapping_mul(other)
+            }
             fn div(self, other: $type) -> Result<$type, TrapKind> {
                 if other == 0 {
                     Err(TrapKind::DivisionByZero)
-				}
-				else {
+                } else {
                     let (result, overflow) = self.overflowing_div(other);
                     if overflow {
                         Err(TrapKind::InvalidConversionToInt)
@@ -704,7 +771,7 @@ macro_rules! impl_integer_arithmetic_ops {
                 }
             }
         }
-	}
+    };
 }
 
 impl_integer_arithmetic_ops!(i32);
@@ -715,12 +782,20 @@ impl_integer_arithmetic_ops!(u64);
 macro_rules! impl_float_arithmetic_ops {
     ($type: ident) => {
         impl ArithmeticOps<$type> for $type {
-			fn add(self, other: $type) -> $type { self + other }
-			fn sub(self, other: $type) -> $type { self - other }
-			fn mul(self, other: $type) -> $type { self * other }
-			fn div(self, other: $type) -> Result<$type, TrapKind> { Ok(self / other) }
+            fn add(self, other: $type) -> $type {
+                self + other
+            }
+            fn sub(self, other: $type) -> $type {
+                self - other
+            }
+            fn mul(self, other: $type) -> $type {
+                self * other
+            }
+            fn div(self, other: $type) -> Result<$type, TrapKind> {
+                Ok(self / other)
             }
         }
+    };
 }
 
 impl_float_arithmetic_ops!(f32);
@@ -731,17 +806,30 @@ impl_float_arithmetic_ops!(F64);
 macro_rules! impl_integer {
     ($type: ident) => {
         impl Integer<$type> for $type {
-			fn leading_zeros(self) -> $type { self.leading_zeros() as $type }
-			fn trailing_zeros(self) -> $type { self.trailing_zeros() as $type }
-			fn count_ones(self) -> $type { self.count_ones() as $type }
-			fn rotl(self, other: $type) -> $type { self.rotate_left(other as u32) }
-			fn rotr(self, other: $type) -> $type { self.rotate_right(other as u32) }
+            fn leading_zeros(self) -> $type {
+                self.leading_zeros() as $type
+            }
+            fn trailing_zeros(self) -> $type {
+                self.trailing_zeros() as $type
+            }
+            fn count_ones(self) -> $type {
+                self.count_ones() as $type
+            }
+            fn rotl(self, other: $type) -> $type {
+                self.rotate_left(other as u32)
+            }
+            fn rotr(self, other: $type) -> $type {
+                self.rotate_right(other as u32)
+            }
             fn rem(self, other: $type) -> Result<$type, TrapKind> {
-				if other == 0 { Err(TrapKind::DivisionByZero) }
-				else { Ok(self.wrapping_rem(other)) }
+                if other == 0 {
+                    Err(TrapKind::DivisionByZero)
+                } else {
+                    Ok(self.wrapping_rem(other))
                 }
             }
         }
+    };
 }
 
 impl_integer!(i32);
@@ -749,34 +837,43 @@ impl_integer!(u32);
 impl_integer!(i64);
 impl_integer!(u64);
 
-macro_rules! impl_float {
-	($type:ident, $int_type:ident) => {
-		impl_float!($type, $type, $int_type);
+macro_rules! call_math {
+    ($op:ident, $e:expr, $fXX:ident, $FXXExt:ident) => {
+        ::libm::$FXXExt::$op($e)
     };
-	($type:ident, $intermediate:ident, $int_type:ident) => {
+}
+
+// We cannot call the math functions directly, because there are multiple available implementaitons in no_std.
+// In std, there are only `Value::$op` and `std::$fXX:$op`.
+// The `std` ones are preferred, because they are not from a trait.
+// For `no_std`, the implementations are `Value::$op` and `libm::FXXExt::$op`,
+// both of which are trait implementations and hence ambiguous.
+// So we have to use a full path, which is what `call_math!` does.
+macro_rules! impl_float {
+    ($type:ident, $fXX:ident, $FXXExt:ident, $iXX:ident) => {
         impl Float<$type> for $type {
             fn abs(self) -> $type {
-				$intermediate::abs(self.into()).into()
+                call_math!(abs, $fXX::from(self), $fXX, $FXXExt).into()
             }
             fn floor(self) -> $type {
-				$intermediate::floor(self.into()).into()
+                call_math!(floor, $fXX::from(self), $fXX, $FXXExt).into()
             }
             fn ceil(self) -> $type {
-				$intermediate::ceil(self.into()).into()
+                call_math!(ceil, $fXX::from(self), $fXX, $FXXExt).into()
             }
             fn trunc(self) -> $type {
-				$intermediate::trunc(self.into()).into()
+                call_math!(trunc, $fXX::from(self), $fXX, $FXXExt).into()
             }
             fn round(self) -> $type {
-				$intermediate::round(self.into()).into()
+                call_math!(round, $fXX::from(self), $fXX, $FXXExt).into()
             }
             fn nearest(self) -> $type {
                 let round = self.round();
-				if self.fract().abs() != 0.5 {
+                if call_math!(fract, $fXX::from(self), $fXX, $FXXExt).abs() != 0.5 {
                     return round;
                 }
 
-				use std::ops::Rem;
+                use core::ops::Rem;
                 if round.rem(2.0) == 1.0 {
                     self.floor()
                 } else if round.rem(2.0) == -1.0 {
@@ -786,34 +883,40 @@ macro_rules! impl_float {
                 }
             }
             fn sqrt(self) -> $type {
-				$intermediate::sqrt(self.into()).into()
+                call_math!(sqrt, $fXX::from(self), $fXX, $FXXExt).into()
             }
             // This instruction corresponds to what is sometimes called "minNaN" in other languages.
             fn min(self, other: $type) -> $type {
-				if self.is_nan() || other.is_nan() {
-					return ::std::$intermediate::NAN.into();
+                if self.is_nan() {
+                    return self;
+                }
+                if other.is_nan() {
+                    return other;
                 }
 
                 self.min(other)
             }
             // This instruction corresponds to what is sometimes called "maxNaN" in other languages.
             fn max(self, other: $type) -> $type {
-				if self.is_nan() || other.is_nan() {
-					return ::std::$intermediate::NAN.into();
+                if self.is_nan() {
+                    return self;
+                }
+                if other.is_nan() {
+                    return other;
                 }
 
                 self.max(other)
             }
             fn copysign(self, other: $type) -> $type {
-				use std::mem::size_of;
+                use core::mem::size_of;
 
                 if self.is_nan() {
                     return self;
                 }
 
-				let sign_mask: $int_type = 1 << ((size_of::<$int_type>() << 3) - 1);
-				let self_int: $int_type = self.transmute_into();
-				let other_int: $int_type = other.transmute_into();
+                let sign_mask: $iXX = 1 << ((size_of::<$iXX>() << 3) - 1);
+                let self_int: $iXX = self.transmute_into();
+                let other_int: $iXX = other.transmute_into();
                 let is_self_sign_set = (self_int & sign_mask) != 0;
                 let is_other_sign_set = (other_int & sign_mask) != 0;
                 if is_self_sign_set == is_other_sign_set {
@@ -828,7 +931,7 @@ macro_rules! impl_float {
     };
 }
 
-impl_float!(f32, i32);
-impl_float!(f64, i64);
-impl_float!(F32, f32, i32);
-impl_float!(F64, f64, i64);
+impl_float!(f32, f32, F32Ext, i32);
+impl_float!(f64, f64, F64Ext, i64);
+impl_float!(F32, f32, F32Ext, i32);
+impl_float!(F64, f64, F64Ext, i64);

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);

tests/spec/run.rs

@@ -1,14 +1,16 @@
 #![cfg(test)]
 
-use std::fs::File;
 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 {
@@ -16,6 +18,7 @@ fn spec_to_runtime_value(val: Value<u32, u64>) -> RuntimeValue {
         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"),
     }
 }
 
@@ -190,7 +193,8 @@ impl SpecDriver {
     fn module_or_last(&self, name: Option<&str>) -> Result<ModuleRef, InterpreterError> {
         match name {
             Some(name) => self.module(name),
-			None => self.last_module
+            None => self
+                .last_module
                 .clone()
                 .ok_or_else(|| InterpreterError::Instantiation("No modules registered".into())),
         }
@@ -301,7 +305,8 @@ fn run_action(
                     "Expected program to have loaded module {:?}",
                     module
                 ));
-			let vec_args = args.iter()
+            let vec_args = args
+                .iter()
                 .cloned()
                 .map(spec_to_runtime_value)
                 .collect::<Vec<_>>();
@@ -345,9 +350,12 @@ fn try_spec(name: &str) -> Result<(), Error> {
     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");
+    spec_file
+        .read_to_end(&mut spec_source)
+        .expect("Can't read file");
 
-	let mut parser = ScriptParser::from_source_and_name(&spec_source, &format!("{}.wast", name)).expect("Can't read spec script");
+    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()? {
@@ -414,12 +422,16 @@ fn try_spec(name: &str) -> Result<(), Error> {
                     Ok(result) => {
                         for actual_result in result.into_iter().collect::<Vec<RuntimeValue>>() {
                             match actual_result {
-								RuntimeValue::F32(val) => if !val.is_nan() {
+                                RuntimeValue::F32(val) => {
+                                    if !val.is_nan() {
                                         panic!("Expected nan value, got {:?}", val)
-								},
-								RuntimeValue::F64(val) => if !val.is_nan() {
+                                    }
+                                }
+                                RuntimeValue::F64(val) => {
+                                    if !val.is_nan() {
                                         panic!("Expected nan value, got {:?}", val)
-								},
+                                    }
+                                }
                                 val @ _ => {
                                     panic!("Expected action to return float value, got {:?}", val)
                                 }
@@ -435,7 +447,7 @@ fn try_spec(name: &str) -> Result<(), Error> {
                 let result = run_action(&mut spec_driver, &action);
                 match result {
                     Ok(result) => panic!("Expected exhaustion, got result: {:?}", result),
-					Err(_e) => {},
+                    Err(_e) => {}
                 }
             }
             CommandKind::AssertTrap { action, .. } => {
@@ -456,13 +468,13 @@ fn try_spec(name: &str) -> Result<(), Error> {
                 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) => {},
+                    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) => {},
+                    Err(_e) => {}
                 }
             }
             CommandKind::Register { name, as_name, .. } => {

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(_));
+    }
+}