Crate web_message

A crate for sending and receiving messages via postMessage.

Any type that implements Message can be serialized and unserialized. Unlike using Serde for JSON encoding, this approach preserves Transferable Objects and can avoid expensive allocations and copying. Unlike using #[wasm-bindgen], this approach works outside of the wasm-bindgen ABI, supporting more types (ex. named enum variants).

For example, the main thread can send a [js_sys::ArrayBuffer] or a Web Worker without copying the data. If the WASM worker only needs to process a few header bytes, it can use the [js_sys::ArrayBuffer] instead of copying into a Vec. The resulting bytes can then be passed to VideoDecoder and the resulting VideoFrame (transferable) can be posted back to the main thread. You can even pass around a [web_sys::MessagePort]!

This crate is designed to be used in conjunction with the web-message-derive crate. We currently attempt parity with ts-rs so the resulting types can use postMessage directly from Typescript.

// NOTE: This is not possible with `wasm-bindgen` or `wasm-bindgen-serde`
#[derive(Message)]
#[msg(tag = "command")]
enum Command {
    Connect {
        url: String,
    },
    Frame {
        keyframe: bool,
        payload: js_sys::ArrayBuffer,
    },
    Close,
}

Some transferable types are gated behind feature flags:

Enums

Error

Traits

Message

Derive Macros

Message