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Wasmi - WebAssembly (Wasm) Interpreter

Wasmi is an efficient and lightweight WebAssembly interpreter with a focus on constrained and embedded systems.

Security Audits

Wasmi is suitable for safety critical use cases and has been audited several times already.

Wasmi Version(s)	Auditor	Contractor	Report
0.36.0-0.38.0	Runtime Verification Inc.	Stellar Development Foundation	PDF
0.31.0	SRLabs	Parity Technologies	PDF

Distinct Features

The following list states some of the distinct features of Wasmi.

• Simple, correct and deterministic execution of WebAssembly.
• Low-overhead and cross-platform WebAssembly runtime for embedded environments.
• JIT bomb resisting translation.
• Loosely mirrors the Wasmtime API.
• 100% WebAssembly spec testsuite compliance.
• Built-in support for fuel metering.
• Supports the official Wasm C-API.

Usage

Refer to the Wasmi usage guide to learn how properly to use Wasmi.

WebAssembly Proposals

The new Wasmi engine supports a variety of WebAssembly proposals and will support even more of them in the future.

WebAssembly Proposal	Status	Comment
mutable-global	✅	≥ 0.14.0.
saturating-float-to-int	✅	≥ 0.14.0.
sign-extension	✅	≥ 0.14.0.
multi-value	✅	≥ 0.14.0.
bulk-memory	✅	≥ 0.24.0. (#628)
reference-types	✅	≥ 0.24.0. (#635)
tail-calls	✅	≥ 0.28.0. (#683)
extended-const	✅	≥ 0.29.0. (#707)
multi-memory	✅	≥ 0.37.0. (#1191)
simd	❌	Unlikely to be supported.
relaxed-simd	❌	Unlikely to be supported. Depends on simd.
function-references	📅	Not yet implemented. (#774)
gc	📅	Not yet implemented. (#775)
threads	📅	Not yet implemented. (#777)
exception-handling	📅	Not yet implemented. (#1037)
custom-page-sizes	📅	Not yet implemented. (#1197)
WASI	👨‍🔬	Experimental support for WASI (wasip1) via the wasmi_wasi crate.
C-API	👨‍🔬	Experimental support for the official Wasm C-API via the wasmi_c_api_impl crate.

Development

Build & Test

Clone the Wasmi repository and build using cargo:

git clone https://github.com/wasmi-labs/wasmi.git --recursive
cd wasmi
cargo build
cargo test

Benchmarks

In order to benchmark Wasmi use the following command:

cargo bench

Use translate, instantiate, execute or overhead filters to only run benchmarks that test performance of Wasm translation, instantiation, execution or miscellaneous overhead respectively, e.g. cargo bench execute.

Supported Platforms

Wasmi supports a wide variety of architectures and platforms.

• Fore more details see this list of supported platforms for Rust.
• Note: Wasmi can be used in no_std embedded environments, thus not requiring the standard library (std).
• Only some platforms are checked in CI and guaranteed to be fully working by the Wasmi maintainers.

License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

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