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3 releases (breaking)

0.42.1 Feb 11, 2021
0.41.0 Mar 4, 2021
0.31.1 Feb 21, 2021

#31 in #wasm-bytecode

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Used in 183 crates (11 directly)




Low-level WebAssembly format library.

Build Status link


Rust WebAssembly format serializing/deserializing

Add to Cargo.toml

tetsy-wasm = "0.42"

and then

let module = tetsy_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

tetsy-wasm supports full wabt testsuite (, running asserts that involves deserialization.

To run testsuite:

  • make sure you have all prerequisites to build wabt (since tetsy-wasm builds it internally using wabt-rs, see
  • checkout with submodules (git submodule update --init --recursive)
  • run cargo test --release --manifest-path=spec/Cargo.toml

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):

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


tetsy-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 tetsy-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