wasi_binio_host and wasi_binio_wasm

wasi_binio_host is the host crate of wasm_binio. Another crate is wasi_binio_wasm which used in wasm module. It creates a call_stub so that host can call a webassembly function with complex data structure arguments and results.

As of today, wasm function can only take i32 i64 f32 f64 types. If you have a function in wasm like this In wasm: do_compute(point1: &Point, point2: &Point)->Rect {...} there is no way to call it directly from host. With the help from wasm_binio, we can instead call the call_stub function and send arguments and results like this

Code in host:

let result: Rect = call_stub(&instance, &(point1, point2), "do_compute")

Code in wasm:

#[no_mangle]
fn do_compute(ptr:i32, buffer_size: i32)->i64{
   let point_tuple : (Point, Point) = wasi_binio_wasm::wasm_deserialize(ptr, buffer_size).unwrap();
   let rect: Rect = some_how_make_a_rect_from_two_points()... /* Your own logic here */
   wasi_binio_wasm::wasm_serialize(&rect).unwrap()
}
Since wasm and wasi are under active development. Wasi will soon provide complex arguments support.
At the time you find this crate, this feature probably have already been supported natively.