9364eb1d98
* Compute instance exports on demand. Instead having instances eagerly compute a Vec of Externs, and bumping the refcount for each Extern, compute Externs on demand. This also enables `Instance::get_export` to avoid doing a linear search. This also means that the closure returned by `get0` and friends now holds an `InstanceHandle` to dynamically hold the instance live rather than being scoped to a lifetime. * Compute module imports and exports on demand too. And compute Extern::ty on demand too. * Add a utility function for computing an ExternType. * Add a utility function for looking up a function's signature. * Add a utility function for computing the ValType of a Global. * Rename wasmtime_environ::Export to EntityIndex. This helps differentiate it from other Export types in the tree, and describes what it is. * Fix a typo in a comment. * Simplify module imports and exports. * Make `Instance::exports` return the export names. This significantly simplifies the public API, as it's relatively common to need the names, and this avoids the need to do a zip with `Module::exports`. This also changes `ImportType` and `ExportType` to have public members instead of private members and accessors, as I find that simplifies the usage particularly in cases where there are temporary instances. * Remove `Instance::module`. This doesn't quite remove `Instance`'s `module` member, it gets a step closer. * Use a InstanceHandle utility function. * Don't consume self in the `Func::get*` methods. Instead, just create a closure containing the instance handle and the export for them to call. * Use `ExactSizeIterator` to avoid needing separate `num_*` methods. * Rename `Extern::func()` etc. to `into_func()` etc. * Revise examples to avoid using `nth`. * Add convenience methods to instance for getting specific extern types. * Use the convenience functions in more tests and examples. * Avoid cloning strings for `ImportType` and `ExportType`. * Remove more obviated clone() calls. * Simplify `Func`'s closure state. * Make wasmtime::Export's fields private. This makes them more consistent with ExportType. * Fix compilation error. * Make a lifetime parameter explicit, and use better lifetime names. Instead of 'me, use 'instance and 'module to make it clear what the lifetime is. * More lifetime cleanups.
49 lines
1.8 KiB
Rust
49 lines
1.8 KiB
Rust
//! Small example of how to instantiate a wasm module that imports one function,
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//! showing how you can fill in host functionality for a wasm module.
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// You can execute this example with `cargo run --example hello`
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use anyhow::Result;
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use wasmtime::*;
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fn main() -> Result<()> {
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// Configure the initial compilation environment, creating the global
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// `Store` structure. Note that you can also tweak configuration settings
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// with a `Config` and an `Engine` if desired.
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println!("Initializing...");
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let store = Store::default();
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// Compile the wasm binary into an in-memory instance of a `Module`.
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println!("Compiling module...");
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let module = Module::from_file(&store, "examples/hello.wat")?;
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// Here we handle the imports of the module, which in this case is our
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// `HelloCallback` type and its associated implementation of `Callback.
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println!("Creating callback...");
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let hello_func = Func::wrap(&store, || {
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println!("Calling back...");
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println!("> Hello World!");
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});
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// Once we've got that all set up we can then move to the instantiation
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// phase, pairing together a compiled module as well as a set of imports.
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// Note that this is where the wasm `start` function, if any, would run.
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println!("Instantiating module...");
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let imports = [hello_func.into()];
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let instance = Instance::new(&module, &imports)?;
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// Next we poke around a bit to extract the `run` function from the module.
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println!("Extracting export...");
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let run = instance
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.get_func("run")
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.ok_or(anyhow::format_err!("failed to find `run` function export"))?
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.get0::<()>()?;
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// And last but not least we can call it!
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println!("Calling export...");
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run()?;
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println!("Done.");
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Ok(())
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}
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