1 unstable release

0.46.0 Feb 4, 2023

#922 in WebAssembly

Used in wasmut




Low-level WebAssembly format library. This is a fork of paritytech/parity-wasm and has been enhanced specifically for wasmut.

crates.io link


Rust WebAssembly format serializing/deserializing

Add to Cargo.toml

wasmut-wasm = "0.42"

and then

let module = wasmut_wasm::deserialize_file("./res/cases/v1/hello.wasm").unwrap();

let code_section = module.code_section().unwrap(); // Part of the module with functions code

println!("Function count in wasm file: {}", code_section.bodies().len());

Wabt Test suite

wasmut-wasm supports full wasm testsuite, running asserts that involves deserialization.

To run testsuite:

  • checkout with submodules (git submodule update --init --recursive)
  • run cargo test --release --workspace

Decoder can be fuzzed with cargo-fuzz using wasm-opt:

  • make sure you have all prerequisites to build binaryen and cargo-fuzz (cmake and a C++11 toolchain)
  • checkout with submodules (git submodule update --init --recursive)
  • install cargo fuzz subcommand with cargo install cargo-fuzz
  • set rustup to use a nightly toolchain, because cargo fuzz uses a rust compiler plugin: rustup override set nightly
  • run cargo fuzz run deserialize

no_std crates

This crate has a feature, std, that is enabled by default. To use this crate in a no_std context, add the following to your Cargo.toml (still requires allocator though):

wasmut-wasm = { version = "0.41", default-features = false }


wasmut-wasm 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.


Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in wasmut-wasm by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

No runtime deps