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63 lines
2.2 KiB
63 lines
2.2 KiB
10 months ago
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use anyhow::Context;
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use std::{fs, path::Path};
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use wasmtime::{
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component::{bindgen, Component, Linker},
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Config, Engine, Result, Store,
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};
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// Generate bindings of the guest and host components.
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bindgen!("convert" in "./examples/component/convert.wit");
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struct HostComponent;
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// Implmentation of the host interface defined in the wit file.
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impl host::Host for HostComponent {
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fn multiply(&mut self, a: f32, b: f32) -> wasmtime::Result<f32> {
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Ok(a * b)
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}
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}
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struct MyState {
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host: HostComponent,
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}
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/// This function is only needed until rust can natively output a component.
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///
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/// Generally embeddings should not be expected to do this programatically, but instead
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/// language specific tooling should be used, for example in Rust `cargo component`
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/// is a good way of doing that: https://github.com/bytecodealliance/cargo-component
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///
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/// In this example we convert the code here to simplify the testing process and build system.
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fn convert_to_component(path: impl AsRef<Path>) -> Result<Vec<u8>> {
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let bytes = &fs::read(&path).context("failed to read input file")?;
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wit_component::ComponentEncoder::default()
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.module(&bytes)?
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.encode()
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}
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fn main() -> Result<()> {
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// Create an engine with the component model enabled (disabled by default).
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let engine = Engine::new(Config::new().wasm_component_model(true))?;
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// NOTE: The wasm32-unknown-unknown target is used here for simplicity, real world use cases
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// should probably use the wasm32-wasi target, and enable wasi preview2 within the component
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// model.
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let component = convert_to_component("target/wasm32-unknown-unknown/debug/guest.wasm")?;
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// Create our component and call our generated host function.
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let component = Component::from_binary(&engine, &component)?;
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let mut store = Store::new(
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&engine,
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MyState {
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host: HostComponent {},
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},
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);
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let mut linker = Linker::new(&engine);
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host::add_to_linker(&mut linker, |state: &mut MyState| &mut state.host)?;
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let (convert, _instance) = Convert::instantiate(&mut store, &component, &linker)?;
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let result = convert.call_convert_celsius_to_fahrenheit(&mut store, 23.4)?;
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println!("Converted to: {:?}", result);
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Ok(())
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}
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