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* 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.
58 lines
1.4 KiB
Markdown
58 lines
1.4 KiB
Markdown
# WebAssembly Text Format (`*.wat`)
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While not necessarily a full-blown language you might be curious how Wasmtime
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interacts with [the `*.wat` text format][spec]! The `wasmtime` CLI and Rust
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embedding API both support the `*.wat` text format by default.
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"Hello, World!" is pretty nontrivial in the `*.wat` format since it's
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assembly-like and not really intended to be a primary programming language. That
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being said we can create a simple add function to call it!
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For example if you have a file `add.wat` like so:
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```wat
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(module
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(func (export "add") (param i32 i32) (result i32)
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local.get 0
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local.get 1
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i32.add))
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```
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Then you can execute this on the CLI with:
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```sh
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$ wasmtime add.wat --invoke add 1 2
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warning: ...
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warning: ...
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3
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```
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And we can see that we're already adding numbers!
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You can also see how this works in the Rust API like so:
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```rust
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# extern crate wasmtime;
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# extern crate anyhow;
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use wasmtime::*;
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# fn main() -> anyhow::Result<()> {
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let store = Store::default();
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let wat = r#"
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(module
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(func (export "add") (param i32 i32) (result i32)
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local.get 0
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local.get 1
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i32.add))
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"#;
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let module = Module::new(&store, wat)?;
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let instance = Instance::new(&module, &[])?;
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let add = instance.get_func("add").unwrap();
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let add = add.get2::<i32, i32, i32>()?;
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println!("1 + 2 = {}", add(1, 2)?);
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# Ok(())
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# }
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```
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[spec]: https://webassembly.github.io/spec/core/text/index.html
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