7c8ac3d71c
Several of the examples wrap the Instance in a HostRef, only to immediately borrow it again to get the exports,and then never touch it again. Simplify this by owning the Instance directly.
70 lines
1.5 KiB
Rust
70 lines
1.5 KiB
Rust
//! Example of instantiating of the WebAssembly module and
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//! invoking its exported function.
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use anyhow::{format_err, Result};
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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() -> Result<()> {
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let wasm = wat::parse_str(WAT)?;
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// Instantiate engine and store.
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let engine = HostRef::new(Engine::default());
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let store = HostRef::new(Store::new(&engine));
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// Load a module.
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let module = HostRef::new(Module::new(&store, &wasm)?);
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// Find index of the `gcd` export.
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let gcd_index = module
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.borrow()
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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(&store, &module, &[])?;
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// Invoke `gcd` export
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let gcd = instance.exports()[gcd_index].func().expect("gcd").clone();
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let result = gcd
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.borrow()
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.call(&[Val::from(6i32), Val::from(27i32)])
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.map_err(|e| format_err!("call error: {:?}", e))?;
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println!("{:?}", result);
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Ok(())
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}
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