#host #wasmer #define #wasmtime #compatible #function #wasm

uptown_funk

Define host functions compatible with Wasmer and Wasmtime

3 releases

0.1.3 Apr 8, 2021
0.1.2 Mar 1, 2021
0.1.1 Jan 26, 2021

#1930 in Rust patterns

Apache-2.0/MIT

21KB
647 lines

uptown_funk is a crate that lets you elegantly define Wasm host functions that are compatible with both Wasmtime and Wasmer runtimes.

It consists of a macro and a few structs/traits that let you translate from Wasm primitive types to higher level Rust types, and back.

Lets look at an example of a host function definition using uptown_funk:

#[host_functions(namespace = "wasi_snapshot_preview1")]
impl WasiState {
    async fn fd_pread(&mut self, fd: u32, iovs: &mut [IoSliceMut<'_>], offset: Filesize) -> (Status, u32) {
        // ...
    }

    // .. Other functions depending on the WasiState struct.
}

The host_function macro lets us grab any host side struct and use it as state for the Wasm instances. Instead of dealing with low level pointers + lengths passed from the WebAssembly guests, we can pretend to receive higher level Rust type (e.g. &mut [IoSliceMut<'_>]) and the macro is going to create appropriate wrappers for us. And of course, it correctly works with async functions on Lunatic.

Dependencies

~1.3–5.5MB
~108K SLoC