16804673a2
* Support parsing the text format in `wasmtime` crate This commit adds support to the `wasmtime::Module` type to parse the text format. This is often quite convenient to support in testing or tinkering with the runtime. Additionally the `wat` parser is pretty lightweight and easy to add to builds, so it's relatively easy for us to support as well! The exact manner that this is now supported comes with a few updates to the existing API: * A new optional feature of the `wasmtime` crate, `wat`, has been added. This is enabled by default. * The `Module::new` API now takes `impl AsRef<[u8]>` instead of just `&[u8]`, and when the `wat` feature is enabled it will attempt to interpret it either as a wasm binary or as the text format. Note that this check is quite cheap since you just check the first byte. * A `Module::from_file` API was added as a convenience to parse a file from disk, allowing error messages for `*.wat` files on disk to be a bit nicer. * APIs like `Module::new_unchecked` and `Module::validate` remain unchanged, they require the binary format to be called. The intention here is to make this as convenient as possible for new developers of the `wasmtime` crate. By changing the default behavior though this has ramifications such as, for example, supporting the text format implicitly through the C API now. * Handle review comments * Update more tests to avoid usage of `wat` crate * Go back to unchecked for now in wasm_module_new Looks like C# tests rely on this?
61 lines
1.4 KiB
Rust
61 lines
1.4 KiB
Rust
//! Example of instantiating of the WebAssembly module and
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//! invoking its exported function.
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use wasmtime::*;
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const WAT: &str = r#"
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(module
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(func $gcd (param i32 i32) (result i32)
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(local i32)
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block ;; label = @1
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block ;; label = @2
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local.get 0
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br_if 0 (;@2;)
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local.get 1
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local.set 2
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br 1 (;@1;)
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end
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loop ;; label = @2
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local.get 1
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local.get 0
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local.tee 2
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i32.rem_u
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local.set 0
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local.get 2
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local.set 1
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local.get 0
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br_if 0 (;@2;)
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end
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end
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local.get 2
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)
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(export "gcd" (func $gcd))
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)
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"#;
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fn main() -> anyhow::Result<()> {
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// Load our WebAssembly (parsed WAT in our case), and then load it into a
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// `Module` which is attached to a `Store` cache.
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let store = Store::default();
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let module = Module::new(&store, WAT)?;
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// Find index of the `gcd` export.
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let gcd_index = module
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.exports()
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.iter()
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.enumerate()
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.find(|(_, export)| export.name().to_string() == "gcd")
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.unwrap()
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.0;
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// Instantiate the module.
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let instance = Instance::new(&module, &[])?;
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// Invoke `gcd` export
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let gcd = instance.exports()[gcd_index].func().expect("gcd");
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let result = gcd.call(&[Val::from(6i32), Val::from(27i32)])?;
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println!("{:?}", result);
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Ok(())
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}
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