b0939f6626
* Remove explicit `S` type parameters This commit removes the explicit `S` type parameter on `Func::typed` and `Instance::get_typed_func`. Historical versions of Rust required that this be a type parameter but recent rustcs support a mixture of explicit type parameters and `impl Trait`. This removes, at callsites, a superfluous `, _` argument which otherwise never needs specification. * Fix mdbook examples
115 lines
3.6 KiB
Rust
115 lines
3.6 KiB
Rust
use anyhow::Error;
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use std::sync::Arc;
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use tokio::time::Duration;
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use wasmtime::{Config, Engine, Linker, Module, Store};
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// For this example we want to use the async version of wasmtime_wasi.
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// Notably, this version of wasi uses a scheduler that will async yield
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// when sleeping in `poll_oneoff`.
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use wasmtime_wasi::{tokio::WasiCtxBuilder, WasiCtx};
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#[tokio::main]
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async fn main() -> Result<(), Error> {
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// Create an environment shared by all wasm execution. This contains
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// the `Engine` and the `Module` we are executing.
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let env = Environment::new()?;
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// The inputs to run_wasm are `Send`: we can create them here and send
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// them to a new task that we spawn.
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let inputs1 = Inputs::new(env.clone(), "Gussie");
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let inputs2 = Inputs::new(env.clone(), "Willa");
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let inputs3 = Inputs::new(env, "Sparky");
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// Spawn some tasks. Insert sleeps before run_wasm so that the
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// interleaving is easy to observe.
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let join1 = tokio::task::spawn(async move { run_wasm(inputs1).await });
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let join2 = tokio::task::spawn(async move {
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tokio::time::sleep(Duration::from_millis(750)).await;
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run_wasm(inputs2).await
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});
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let join3 = tokio::task::spawn(async move {
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tokio::time::sleep(Duration::from_millis(1250)).await;
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run_wasm(inputs3).await
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});
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// All tasks should join successfully.
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join1.await??;
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join2.await??;
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join3.await??;
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Ok(())
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}
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#[derive(Clone)]
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struct Environment {
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engine: Engine,
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module: Module,
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linker: Arc<Linker<WasiCtx>>,
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}
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impl Environment {
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pub fn new() -> Result<Self, Error> {
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let mut config = Config::new();
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// We need this engine's `Store`s to be async, and consume fuel, so
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// that they can co-operatively yield during execution.
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config.async_support(true);
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config.consume_fuel(true);
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let engine = Engine::new(&config)?;
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let module = Module::from_file(&engine, "target/wasm32-wasi/debug/tokio-wasi.wasm")?;
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// A `Linker` is shared in the environment amongst all stores, and this
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// linker is used to instantiate the `module` above. This example only
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// adds WASI functions to the linker, notably the async versions built
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// on tokio.
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let mut linker = Linker::new(&engine);
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wasmtime_wasi::tokio::add_to_linker(&mut linker, |cx| cx)?;
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Ok(Self {
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engine,
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module,
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linker: Arc::new(linker),
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})
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}
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}
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struct Inputs {
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env: Environment,
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name: String,
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}
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impl Inputs {
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fn new(env: Environment, name: &str) -> Self {
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Self {
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env,
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name: name.to_owned(),
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}
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}
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}
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async fn run_wasm(inputs: Inputs) -> Result<(), Error> {
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let wasi = WasiCtxBuilder::new()
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// Let wasi print to this process's stdout.
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.inherit_stdout()
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// Set an environment variable so the wasm knows its name.
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.env("NAME", &inputs.name)?
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.build();
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let mut store = Store::new(&inputs.env.engine, wasi);
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// WebAssembly execution will be paused for an async yield every time it
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// consumes 10000 fuel. Fuel will be refilled u64::MAX times.
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store.out_of_fuel_async_yield(u64::MAX, 10000);
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// Instantiate into our own unique store using the shared linker, afterwards
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// acquiring the `_start` function for the module and executing it.
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let instance = inputs
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.env
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.linker
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.instantiate_async(&mut store, &inputs.env.module)
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.await?;
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instance
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.get_typed_func::<(), ()>(&mut store, "_start")?
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.call_async(&mut store, ())
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.await?;
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Ok(())
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}
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