Function add_to_linker_async

pub fn add_to_linker_async<T: Send>(
    linker: &mut Linker<T>,
    f: impl Fn(&mut T) -> &mut WasiP1Ctx + Copy + Send + Sync + 'static,
) -> Result<()>

Available on crate feature preview1 only.

Adds asynchronous versions of all WASIp1 functions to the wasmtime::Linker provided.

This method will add WASIp1 functions to linker. Access to WasiP1Ctx is provided with f by projecting from the store-local state of T to WasiP1Ctx. The closure f is invoked every time a WASIp1 function is called to get access to [WASIp1] from T. The returned WasiP1Ctx is used to implement I/O and controls what each function will return.

It’s recommended that WasiP1Ctx is stored as a field in T or that T = WasiP1Ctx itself. The closure f should be a small projection (e.g. &mut arg.field) or something otherwise “small” as it will be executed every time a WASI call is made.

Note that this function is intended for use with Config::async_support(true). If you’re looking for a synchronous version see add_to_linker_sync.

Examples

If the T in Linker<T> is just WasiP1Ctx:

use wasmtime::{Result, Linker, Engine, Config};
use wasmtime_wasi::preview1::{self, WasiP1Ctx};

fn main() -> Result<()> {
    let mut config = Config::new();
    config.async_support(true);
    let engine = Engine::new(&config)?;

    let mut linker: Linker<WasiP1Ctx> = Linker::new(&engine);
    preview1::add_to_linker_async(&mut linker, |cx| cx)?;

    // ... continue to add more to `linker` as necessary and use it ...

    Ok(())
}

If the T in Linker<T> is custom state:

use wasmtime::{Result, Linker, Engine, Config};
use wasmtime_wasi::preview1::{self, WasiP1Ctx};

struct MyState {
    // .. other custom state here ..

    wasi: WasiP1Ctx,
}

fn main() -> Result<()> {
    let mut config = Config::new();
    config.async_support(true);
    let engine = Engine::new(&config)?;

    let mut linker: Linker<MyState> = Linker::new(&engine);
    preview1::add_to_linker_async(&mut linker, |cx| &mut cx.wasi)?;

    // ... continue to add more to `linker` as necessary and use it ...

    Ok(())
}