1 use std::{fs, path::Path};
2 use wasmtime::{
3 Config, Engine, Result, Store, ToWasmtimeResult as _,
4 component::{Component, HasSelf, Linker, bindgen},
5 error::Context as _,
6 };
7
8 // Generate bindings of the guest and host components.
9 bindgen!("convert" in "./examples/component/convert.wit");
10
11 struct MyState {
12 // ..
13 }
14
15 // Implementation of the host interface defined in the wit file.
16 impl host::Host for MyState {
multiply(&mut self, a: f32, b: f32) -> f3217 fn multiply(&mut self, a: f32, b: f32) -> f32 {
18 a * b
19 }
20 }
21
22 /// This function is only needed until rust can natively output a component.
23 ///
24 /// Generally embeddings should not be expected to do this programmatically, but instead
25 /// language specific tooling should be used, for example in Rust `cargo component`
26 /// is a good way of doing that: https://github.com/bytecodealliance/cargo-component
27 ///
28 /// In this example we convert the code here to simplify the testing process and build system.
convert_to_component(path: impl AsRef<Path>) -> Result<Vec<u8>>29 fn convert_to_component(path: impl AsRef<Path>) -> Result<Vec<u8>> {
30 let bytes = &fs::read(&path).context("failed to read input file")?;
31 wit_component::ComponentEncoder::default()
32 .module(&bytes)
33 .to_wasmtime_result()?
34 .encode()
35 .to_wasmtime_result()
36 }
37
main() -> Result<()>38 fn main() -> Result<()> {
39 // Create an engine with the component model enabled (disabled by default).
40 let engine = Engine::new(Config::new().wasm_component_model(true))?;
41
42 // NOTE: The wasm32-unknown-unknown target is used here for simplicity, real world use cases
43 // should probably use the wasm32-wasip1 target, and enable wasi preview2 within the component
44 // model.
45 let component = convert_to_component("target/wasm32-unknown-unknown/debug/guest.wasm")?;
46
47 // Create our component and call our generated host function.
48 let component = Component::from_binary(&engine, &component)?;
49 let mut store = Store::new(&engine, MyState {});
50 let mut linker = Linker::new(&engine);
51 host::add_to_linker::<_, HasSelf<_>>(&mut linker, |state| state)?;
52 let convert = Convert::instantiate(&mut store, &component, &linker)?;
53 let result = convert.call_convert_celsius_to_fahrenheit(&mut store, 23.4)?;
54 println!("Converted to: {result:?}");
55 Ok(())
56 }
57