Function callback

crates/guest-rust/src/rt/async_support.rs:510–534

(event0: u32, event1: u32, event2: u32)

/// This function assumes that `context_get()` returns a `FutureState`.
#[doc(hidden)]
pub unsafe fn callback(event0: u32, event1: u32, event2: u32) -> u32 {
    // Acquire our context-local state, assert it's not-null, and then reset
    // the state to null while we're running to help prevent any unintended
    // usage.
    let state = context_get().cast::<FutureState<'static>>();
    assert!(!state.is_null());
    unsafe {
        context_set(ptr::null_mut());
    }

    // Use `state` to run the `callback` function in the context of our event
    // codes we received. If the callback decides to exit then we're done with
    // our future so deallocate it. Otherwise put our future back in
    // context-local storage and forward the code.
    unsafe {
        let rc = (*state).callback(event0, event1, event2);
        if rc == CallbackCode::Exit {
            drop(Box::from_raw(state));
        } else {
            context_set(state.cast());
        }
        rtdebug!(" => (cb) {rc:?}");
        rc.encode()
    }
}

/// Run the specified future to completion, returning the result.
///