12 unstable releases (4 breaking)

0.4.3 Jan 3, 2019
0.4.2 Nov 15, 2018
0.4.1 Oct 2, 2018
0.4.0 Jul 31, 2018
0.1.1 Mar 24, 2018

#3 in WebAssembly

Download history 763/week @ 2018-10-21 869/week @ 2018-10-28 1080/week @ 2018-11-04 985/week @ 2018-11-11 1111/week @ 2018-11-18 1074/week @ 2018-11-25 1286/week @ 2018-12-02 1146/week @ 2018-12-09 1462/week @ 2018-12-16 2497/week @ 2018-12-23 944/week @ 2018-12-30 2375/week @ 2019-01-06 2620/week @ 2019-01-13

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Used in 2 crates (1 directly)



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WASM interpreter (previously lived in parity-wasm)

Primary purpose of wasmi is to be used with parity (ethereum-like contracts in wasm) and with Polkadot. However, wasmi is designed to be as flexible as possible and might be suited well for other purposes.

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.


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.

Build & Test

As wasmi contains a git submodule, you need to use --recursive for cloning or to checkout the submodule explicitly, otherwise the testing would fail.

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

no_std support

This crate supports no_std environments. Enable the core feature and disable default features:

parity-wasm = {
	version = "0.31",
	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, 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.


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


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