7a1b7cdf92
Implement Wasmtime's new API as designed by RFC 11. This is quite a large commit which has had lots of discussion externally, so for more information it's best to read the RFC thread and the PR thread.
73 lines
2.0 KiB
Markdown
73 lines
2.0 KiB
Markdown
# WASI
|
|
|
|
You can also [browse this source code online][code] and clone the wasmtime
|
|
repository to run the example locally.
|
|
|
|
[code]: https://github.com/bytecodealliance/wasmtime/blob/main/examples/wasi/main.rs
|
|
|
|
This example shows how to use the [`wasmtime-wasi`] crate to define WASI
|
|
functions within a [`Linker`] which can then be used to instantiate a
|
|
WebAssembly module.
|
|
|
|
[`wasmtime-wasi`]: https://crates.io/crates/wasmtime-wasi
|
|
[`Linker`]: https://docs.rs/wasmtime/*/wasmtime/struct.Linker.html
|
|
|
|
## Wasm Source code
|
|
|
|
```rust
|
|
{{#include ../examples/wasi/wasm/wasi.rs}}
|
|
```
|
|
|
|
## `wasi.rs`
|
|
|
|
```rust,ignore
|
|
{{#include ../examples/wasi/main.rs}}
|
|
```
|
|
|
|
## WASI state with other custom host state
|
|
|
|
The [`add_to_linker`] takes a second argument which is a closure to access `&mut
|
|
WasiCtx` from within the `T` stored in the `Store<T>` itself. In the above
|
|
example this is trivial because the `T` in `Store<T>` is `WasiCtx` itself, but
|
|
you can also store other state in `Store` like so:
|
|
|
|
[`add_to_linker`]: https://docs.rs/wasmtime-wasi/*/wasmtime_wasi/sync/fn.add_to_linker.html
|
|
[`Store`]: https://docs.rs/wasmtime/0.26.0/wasmtime/struct.Store.html
|
|
[`BorrowMut<WasiCtx>`]: https://doc.rust-lang.org/stable/std/borrow/trait.BorrowMut.html
|
|
[`WasiCtx`]: https://docs.rs/wasmtime-wasi/*/wasmtime_wasi/struct.WasiCtx.html
|
|
|
|
```rust
|
|
# extern crate wasmtime;
|
|
# extern crate wasmtime_wasi;
|
|
# extern crate anyhow;
|
|
use anyhow::Result;
|
|
use std::borrow::{Borrow, BorrowMut};
|
|
use wasmtime::*;
|
|
use wasmtime_wasi::{WasiCtx, sync::WasiCtxBuilder};
|
|
|
|
struct MyState {
|
|
message: String,
|
|
wasi: WasiCtx,
|
|
}
|
|
|
|
fn main() -> Result<()> {
|
|
let engine = Engine::default();
|
|
let mut linker = Linker::new(&engine);
|
|
wasmtime_wasi::add_to_linker(&mut linker, |state: &mut MyState| &mut state.wasi)?;
|
|
|
|
let wasi = WasiCtxBuilder::new()
|
|
.inherit_stdio()
|
|
.inherit_args()?
|
|
.build();
|
|
let mut store = Store::new(&engine, MyState {
|
|
message: format!("hello!"),
|
|
wasi,
|
|
});
|
|
|
|
// ...
|
|
|
|
# let _linker: Linker<MyState> = linker;
|
|
Ok(())
|
|
}
|
|
```
|