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    //! # wasmi
    //!
    //! 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 is designed for efficient execution.
    //!
    //! Wasm code is distributed in the form of modules that contains definitions of:
    //!
    //! - functions,
    //! - global variables,
    //! - linear memory instances and
    //! - tables.
    //!
    //! Each of these definitions can be imported and exported.
    //!
    //! In addition to these definitions, modules can define initialization data for their memory or tables. This initialization data can take the
    //! form of segments, copied to given offsets. They can also define a `start` function that is automatically executed when the module is loaded.
    //!
    //! ## Loading and Validation
    //!
    //! Before execution, a module must be validated. This process checks that the module is well-formed
    //! and makes only allowed operations.
    //!
    //! 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 instantiated.
    //! Instantiation includes the following steps:
    //!
    //! 1. Creating an empty module instance.
    //! 2. Resolving the definition instances for each declared import in the module.
    //! 3. Instantiating definitions declared in the module (e.g. allocate global variables, allocate linear memory, etc.).
    //! 4. Initializing memory and table contents by copying segments into them.
    //! 5. Executing the `start` function, if any.
    //!
    //! After these steps, the module instance is ready to execute functions.
    //!
    //! ## Execution
    //!
    //! It only is allowed to call functions which are exported by the module.
    //! Functions can either return a result or trap (e.g. there can't be linking error in the middle of the function execution).
    //! This property is ensured by the validation process.
    //!
    //! # Examples
    //!
    //! ```rust
    //! extern crate wasmi;
    //! extern crate wabt;
    //!
    //! use wasmi::{ModuleInstance, ImportsBuilder, NopExternals, RuntimeValue};
    //!
    //! fn main() {
    //!     // Parse WAT (WebAssembly Text format) into wasm bytecode.
    //!     let wasm_binary: Vec<u8> =
    //!         wabt::wat2wasm(
    //!             r#"
    //!             (module
    //!                 (func (export "test") (result i32)
    //!                     i32.const 1337
    //!                 )
    //!             )
    //!             "#,
    //!         )
    //!         .expect("failed to parse wat");
    //!
    //!     // Load wasm binary and prepare it for instantiation.
    //!     let module = wasmi::Module::from_buffer(&wasm_binary)
    //!         .expect("failed to load wasm");
    //!
    //!     // Instantiate a module with empty imports and
    //!     // assert that there is no `start` function.
    //!     let instance =
    //!         ModuleInstance::new(
    //!             &module,
    //!             &ImportsBuilder::default()
    //!         )
    //!         .expect("failed to instantiate wasm module")
    //!         .assert_no_start();
    //!
    //!     // Finally, invoke the exported function "test" with no parameters
    //!     // and empty external function executor.
    //!     assert_eq!(
    //!         instance.invoke_export(
    //!             "test",
    //!             &[],
    //!             &mut NopExternals,
    //!         ).expect("failed to execute export"),
    //!         Some(RuntimeValue::I32(1337)),
    //!     );
    //! }
    //! ```

    #![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;

    extern crate memory_units as memory_units_crate;
    extern crate parity_wasm;

    extern crate wasmi_validation as validation;

    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.
    /// Traps can't be handled by WebAssembly code, but are reported to the embedder.
    #[derive(Debug)]
    pub struct Trap {
        kind: TrapKind,
    }

    impl Trap {
        /// Create new trap.
        pub fn new(kind: TrapKind) -> Trap {
            Trap { kind }
        }

        /// Returns kind of this trap.
        pub fn kind(&self) -> &TrapKind {
            &self.kind
        }
    }

    impl fmt::Display for Trap {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            write!(f, "Trap: {:?}", self.kind)
        }
    }

    #[cfg(feature = "std")]
    impl error::Error for Trap {
        fn description(&self) -> &str {
            "runtime trap"
        }
    }

    /// Error type which can be thrown by wasm code or by host environment.
    ///
    /// See [`Trap`] for details.
    ///
    /// [`Trap`]: struct.Trap.html
    #[derive(Debug)]
    pub enum TrapKind {
        /// Wasm code executed `unreachable` opcode.
        ///
        /// `unreachable` is a special opcode which always traps upon execution.
        /// This opcode have a similar purpose as `ud2` in x86.
        Unreachable,

        /// Attempt to load or store at the address which
        /// lies outside of bounds of the memory.
        ///
        /// Since addresses are interpreted as unsigned integers, out of bounds access
        /// can't happen with negative addresses (i.e. they will always wrap).
        MemoryAccessOutOfBounds,

        /// Attempt to access table element at index which
        /// lies outside of bounds.
        ///
        /// This typically can happen when `call_indirect` is executed
        /// with index that lies out of bounds.
        ///
        /// Since indexes are interpreted as unsinged integers, out of bounds access
        /// can't happen with negative indexes (i.e. they will always wrap).
        TableAccessOutOfBounds,

        /// Attempt to access table element which is uninitialized (i.e. `None`).
        ///
        /// This typically can happen when `call_indirect` is executed.
        ElemUninitialized,

        /// Attempt to divide by zero.
        ///
        /// This trap typically can happen if `div` or `rem` is executed with
        /// zero as divider.
        DivisionByZero,

        /// Attempt to make a conversion to an int failed.
        ///
        /// This can happen when:
        ///
        /// - trying to do signed division (or get the remainder) -2<sup>N-1</sup> over -1. This is
        ///   because the result +2<sup>N-1</sup> isn't representable as a N-bit signed integer.
        /// - trying to truncate NaNs, infinity, or value for which the result is out of range into an integer.
        InvalidConversionToInt,

        /// Stack overflow.
        ///
        /// This is likely caused by some infinite or very deep recursion.
        /// Extensive inlining might also be the cause of stack overflow.
        StackOverflow,

        /// Attempt to invoke a function with mismatching signature.
        ///
        /// This can happen if [`FuncInstance`] was invoked
        /// with mismatching [signature][`Signature`].
        ///
        /// This can always happen with indirect calls. `call_indirect` instruction always
        /// specifies the expected signature of function. If `call_indirect` is executed
        /// with index that points on function with signature different that is
        /// expected by this `call_indirect`, this trap is raised.
        ///
        /// [`Signature`]: struct.Signature.html
        UnexpectedSignature,

        /// Error specified by the host.
        ///
        /// Typically returned from an implementation of [`Externals`].
        ///
        /// [`Externals`]: trait.Externals.html
        Host(Box<dyn host::HostError>),
    }

    impl TrapKind {
        /// Whether this trap is specified by the host.
        pub fn is_host(&self) -> bool {
            match self {
                &TrapKind::Host(_) => true,
                _ => false,
            }
        }
    }

    /// Internal interpreter error.
    #[derive(Debug)]
    pub enum Error {
        /// Module validation error. Might occur only at load time.
        Validation(String),
        /// Error while instantiating a module. Might occur when provided
        /// with incorrect exports (i.e. linkage failure).
        Instantiation(String),
        /// Function-level error.
        Function(String),
        /// Table-level error.
        Table(String),
        /// Memory-level error.
        Memory(String),
        /// Global-level error.
        Global(String),
        /// Value-level error.
        Value(String),
        /// Trap.
        Trap(Trap),
        /// Custom embedder error.
        Host(Box<dyn host::HostError>),
    }

    impl Error {
        /// Returns [`HostError`] if this `Error` represents some host error.
        ///
        /// I.e. if this error have variant [`Host`] or [`Trap`][`Trap`] with [host][`TrapKind::Host`] error.
        ///
        /// [`HostError`]: trait.HostError.html
        /// [`Host`]: enum.Error.html#variant.Host
        /// [`Trap`]: enum.Error.html#variant.Trap
        /// [`TrapKind::Host`]: enum.TrapKind.html#variant.Host
        pub fn as_host_error(&self) -> Option<&dyn host::HostError> {
            match *self {
                Error::Host(ref host_err) => Some(&**host_err),
                Error::Trap(ref trap) => match *trap.kind() {
                    TrapKind::Host(ref host_err) => Some(&**host_err),
                    _ => None,
                },
                _ => None,
            }
        }
    }

    impl Into<String> for Error {
        fn into(self) -> String {
            match self {
                Error::Validation(s) => s,
                Error::Instantiation(s) => s,
                Error::Function(s) => s,
                Error::Table(s) => s,
                Error::Memory(s) => s,
                Error::Global(s) => s,
                Error::Value(s) => s,
                Error::Trap(s) => format!("trap: {:?}", s),
                Error::Host(e) => format!("user: {}", e),
            }
        }
    }

    impl fmt::Display for Error {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            match *self {
                Error::Validation(ref s) => write!(f, "Validation: {}", s),
                Error::Instantiation(ref s) => write!(f, "Instantiation: {}", s),
                Error::Function(ref s) => write!(f, "Function: {}", s),
                Error::Table(ref s) => write!(f, "Table: {}", s),
                Error::Memory(ref s) => write!(f, "Memory: {}", s),
                Error::Global(ref s) => write!(f, "Global: {}", s),
                Error::Value(ref s) => write!(f, "Value: {}", s),
                Error::Trap(ref s) => write!(f, "Trap: {:?}", s),
                Error::Host(ref e) => write!(f, "User: {}", e),
            }
        }
    }

    #[cfg(feature = "std")]
    impl error::Error for Error {
        fn description(&self) -> &str {
            match *self {
                Error::Validation(ref s) => s,
                Error::Instantiation(ref s) => s,
                Error::Function(ref s) => s,
                Error::Table(ref s) => s,
                Error::Memory(ref s) => s,
                Error::Global(ref s) => s,
                Error::Value(ref s) => s,
                Error::Trap(_) => "Trap",
                Error::Host(_) => "Host error",
            }
        }
    }

    impl<U> From<U> for Error
    where
        U: host::HostError + Sized,
    {
        fn from(e: U) -> Self {
            Error::Host(Box::new(e))
        }
    }

    impl<U> From<U> for Trap
    where
        U: host::HostError + Sized,
    {
        fn from(e: U) -> Self {
            Trap::new(TrapKind::Host(Box::new(e)))
        }
    }

    impl From<Trap> for Error {
        fn from(e: Trap) -> Error {
            Error::Trap(e)
        }
    }

    impl From<TrapKind> for Trap {
        fn from(e: TrapKind) -> Trap {
            Trap::new(e)
        }
    }

    impl From<validation::Error> for Error {
        fn from(e: validation::Error) -> Error {
            Error::Validation(e.to_string())
        }
    }

    mod func;
    mod global;
    mod host;
    mod imports;
    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::func::{FuncInstance, FuncInvocation, FuncRef, ResumableError};
    pub use self::global::{GlobalInstance, GlobalRef};
    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::{size_of, ByteSize, Bytes, RoundUpTo};
    }

    /// Deserialized module prepared for instantiation.
    pub struct Module {
        code_map: Vec<isa::Instructions>,
        module: parity_wasm::elements::Module,
    }

    impl Module {
        /// Create `Module` from `parity_wasm::elements::Module`.
        ///
        /// This function will load, validate and prepare a `parity_wasm`'s `Module`.
        ///
        /// # Errors
        ///
        /// Returns `Err` if provided `Module` is not valid.
        ///
        /// # Examples
        ///
        /// ```rust
        /// extern crate parity_wasm;
        /// extern crate wasmi;
        ///
        /// use parity_wasm::builder;
        /// use parity_wasm::elements;
        ///
        /// fn main() {
        ///     let parity_module =
        ///         builder::module()
        ///             .function()
        ///                 .signature().with_param(elements::ValueType::I32).build()
        ///                 .body().build()
        ///             .build()
        ///         .build();
        ///
        ///     let module = wasmi::Module::from_parity_wasm_module(parity_module)
        ///         .expect("parity-wasm builder generated invalid module!");
        ///
        ///     // Instantiate `module`, etc...
        /// }
        /// ```
        pub fn from_parity_wasm_module(module: parity_wasm::elements::Module) -> Result<Module, Error> {
            let prepare::CompiledModule { code_map, module } = prepare::compile_module(module)?;

            Ok(Module { code_map, module })
        }

        /// Fail if the module contains any floating-point operations
        ///
        /// # Errors
        ///
        /// Returns `Err` if provided `Module` is not valid.
        ///
        /// # Examples
        ///
        /// ```rust
        /// # extern crate wasmi;
        /// # extern crate wabt;
        ///
        /// let wasm_binary: Vec<u8> =
        ///     wabt::wat2wasm(
        ///         r#"
        ///         (module
        ///          (func $add (param $lhs i32) (param $rhs i32) (result i32)
        ///                get_local $lhs
        ///                get_local $rhs
        ///                i32.add))
        ///         "#,
        ///     )
        ///     .expect("failed to parse wat");
        ///
        /// // Load wasm binary and prepare it for instantiation.
        /// let module = wasmi::Module::from_buffer(&wasm_binary).expect("Parsing failed");
        /// assert!(module.deny_floating_point().is_ok());
        ///
        /// let wasm_binary: Vec<u8> =
        ///     wabt::wat2wasm(
        ///         r#"
        ///         (module
        ///          (func $add (param $lhs f32) (param $rhs f32) (result f32)
        ///                get_local $lhs
        ///                get_local $rhs
        ///                f32.add))
        ///         "#,
        ///     )
        ///     .expect("failed to parse wat");
        ///
        /// let module = wasmi::Module::from_buffer(&wasm_binary).expect("Parsing failed");
        /// assert!(module.deny_floating_point().is_err());
        ///
        /// let wasm_binary: Vec<u8> =
        ///     wabt::wat2wasm(
        ///         r#"
        ///         (module
        ///          (func $add (param $lhs f32) (param $rhs f32) (result f32)
        ///                get_local $lhs))
        ///         "#,
        ///     )
        ///     .expect("failed to parse wat");
        ///
        /// let module = wasmi::Module::from_buffer(&wasm_binary).expect("Parsing failed");
        /// assert!(module.deny_floating_point().is_err());
        /// ```
        pub fn deny_floating_point(&self) -> Result<(), Error> {
            prepare::deny_floating_point(&self.module).map_err(Into::into)
        }

        /// Create `Module` from a given buffer.
        ///
        /// This function will deserialize wasm module from a given module,
        /// validate and prepare it for instantiation.
        ///
        /// # Errors
        ///
        /// Returns `Err` if wasm binary in provided `buffer` is not valid wasm binary.
        ///
        /// # Examples
        ///
        /// ```rust
        /// extern crate wasmi;
        ///
        /// fn main() {
        ///     let module =
        ///         wasmi::Module::from_buffer(
        ///             // Minimal module:
        ///             //   \0asm - magic
        ///             //    0x01 - version (in little-endian)
        ///             &[0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00]
        ///         ).expect("Failed to load minimal module");
        ///
        ///     // Instantiate `module`, etc...
        /// }
        /// ```
        pub fn from_buffer<B: AsRef<[u8]>>(buffer: B) -> Result<Module, Error> {
            let module = parity_wasm::elements::deserialize_buffer(buffer.as_ref())
                .map_err(|e: parity_wasm::elements::Error| Error::Validation(e.to_string()))?;
            Module::from_parity_wasm_module(module)
        }

        pub(crate) fn module(&self) -> &parity_wasm::elements::Module {
            &self.module
        }

        pub(crate) fn code(&self) -> &Vec<isa::Instructions> {
            &self.code_map
        }
    }

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  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g., `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g., `vec -> usize` or `* -> vec`)

Search multiple things at once by splitting your query with comma (e.g., `str,u8` or `String,struct:Vec,test`)