Crate poll_promise

poll-promise is a Rust crate for polling the result of a concurrent (e.g. async) operation.

It is particularly useful in games and immediate mode GUI:s, where one often wants to start a background operation and then ask “are we there yet?” on each subsequent frame until the operation completes.

Example:

let promise = Promise::spawn_thread("slow_operation", something_slow);

// Then in the game loop or immediate mode GUI code:
if let Some(result) = promise.ready() {
    // Use/show result
} else {
    // Show a loading screen
}

Features

poll-promise can be used with any async runtime (or without one!), but a few convenience methods are added when compiled with the following features:

• async-std — If you enable the async-std feature you can use Promise::spawn_async and Promise::spawn_blocking which will spawn tasks in the surrounding async-std runtime.

• smol — If you enable the smol feature you can use Promise::spawn_async and Promise::spawn_local which will spawn tasks using the smol executor. Remember to tick the smol executor with tick and tick_local.

• smol_tick_poll — Enabling the smol_tick_poll feature (together with smol) calling Promise::poll will automatically tick the smol executor. This means you do not have to worry about calling tick but comes at the cost of loss of finer control over the executor.

  Since calling tick_local will block the current thread, running multiple local promises at once with smol_tick_poll enabled may also cause stuttering.

  poll-promise will automatically tick the smol executor with this feature disabled for you when using Promise::block_until_ready and friends, however.

• tokio — If you enable the tokio feature you can use Promise::spawn_async, Promise::spawn_local and Promise::spawn_blocking which will spawn tasks in the surrounding tokio runtime.

• web — If you enable the web feature you can use Promise::spawn_local which will spawn tasks using wasm_bindgen_futures::spawn_local.

Structs

• Promise
  A promise that waits for the reception of a single value, presumably from some async task.
• Sender
  Used to send a result to a Promise.

Enums

• TaskType
  The type of a running task.

Functions

• ticksmol
  ‘Tick’ the smol thread executor.
• tick_localsmol
  ‘Tick’ the smol local thread executor.