d1b1500d19
This commit adds a `wasmtime-rust` crate to the `misc` folder next to the previously added Python extension. The intention is that this showcases loading a WebAssembly file natively in Rust and how with an attribute macro it can feel lightweight in terms of boilerplate. The macro itself is pretty non-featureful today beyond the bare bones to get anything working, but there's all sorts of possibilities like JIT-compiled entry stubs we could eventually do with all the type information!
38 lines
1.3 KiB
Markdown
38 lines
1.3 KiB
Markdown
# `wasmtime-rust` - Using WebAssembly from Rust
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This crate is intended to be an example of how to load WebAssembly files from a
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native Rust application. You can always use `wasmtime` and its family of crates
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directly, but the purpose of this crate is to provide an ergonomic macro:
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```rust
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#[wasmtime_rust::wasmtime]
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trait WasmMarkdown {
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fn render(&mut self, input: &str) -> String;
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}
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fn main() -> Result<(), failure::Error> {
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let mut markdown = WasmMarkdown::load_file("markdown.wasm")?;
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println!("{}", markdown.render("# Hello, Rust!"));
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Ok(())
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}
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```
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The `wasmtime` macro defined in the `wasmtime-rust` crate is placed on a `trait`
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which includes the set of functionality which a wasm module should export. In
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this case we're expecting one `render` function which takes and returns a
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string.
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The macro expands to a `struct` with all of the methods on the trait (they must
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all be `&mut self`) and one function called `load_file` to actually instantiate
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the module.
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Note that this macro is still in early stages of development, so error messages
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aren't great yet and all functionality isn't supported yet.
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## Missing features
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Currently if the wasm module imports any symbols outside of the WASI namespace
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the module will not load. It's intended that support for this will be added soon
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though!
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