wasi 0.12.1+wasi-0.2.0

WASI API bindings for Rust
Documentation

A Bytecode Alliance project

This crate contains bindings for WASI APIs for the worlds:

This crate is procedurally generated from WIT files using wit-bindgen.

Usage

First you can depend on this crate via Cargo.toml:

[dependencies]
wasi = "0.12.0"

Next you can use the APIs in the root of the module like so:

fn main() {
    let stdout = wasi::cli::stdout::get_stdout();
    stdout.blocking_write_and_flush(b"Hello, world!\n").unwrap();
}

This crate is intended to target components but today you need to go through the intermediate build step of a core WebAssembly module using the wasm32-wasi target:

$ cargo build --target wasm32-wasi

Next you'll want an "adapter" to convert the Rust standard library's usage of wasi_snapshot_preview1 to the component model. An example adapter can be found from Wasmtime's release page.

$ curl -LO https://github.com/bytecodealliance/wasmtime/releases/download/v17.0.0/wasi_snapshot_preview1.command.wasm

Next to create a component you'll use the wasm-tools CLI to create a component:

$ cargo install wasm-tools
$ wasm-tools component new target/wasm32-wasi/debug/foo.wasm \
    --adapt ./wasi_snapshot_preview1.command.wasm \
    -o component.wasm

And finally the component can be run by a runtime that has Component Model support, such as Wasmtime:

$ wasmtime run component.wasm
Hello, world!

Development

The bulk of the wasi crate is generated by the wit-bindgen tool. The src/bindings.rs file can be regenerated with:

$ ./ci/regenerate.sh

WASI definitions are located in the wit directory of this repository. Currently they're copied from upstream repositories but are hoped to be better managed in the future.

License

This project is triple licenced under the Apache 2/ Apache 2 with LLVM exceptions/ MIT licences. The reasoning for this is:

  • Apache 2/ MIT is common in the rust ecosystem.
  • Apache 2/ MIT is used in the rust standard library, and some of this code may be migrated there.
  • Some of this code may be used in compiler output, and the Apache 2 with LLVM exceptions licence is useful for this.

For more details see

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this project by you, as defined in the Apache 2/ Apache 2 with LLVM exceptions/ MIT licenses, shall be licensed as above, without any additional terms or conditions.