agnostic_lite/

wasm.rs

cfg_time!(
  mod after;
  mod delay;
  mod interval;
  mod sleep;
  mod timeout;

  pub use after::*;
  pub use delay::*;
  pub use interval::*;
  pub use sleep::*;
  pub use timeout::*;

  use std::time::{Duration, Instant};
);

use core::{
  future::Future,
  pin::Pin,
  task::{Context, Poll},
};

use wasm::channel::*;

use super::handle::JoinError;
use crate::{AsyncBlockingSpawner, AsyncLocalSpawner, AsyncSpawner, Yielder};

/// The join handle returned by [`WasmSpawner`].
pub struct JoinHandle<F> {
  pub(crate) stop_tx: oneshot::Sender<bool>,
  pub(crate) rx: oneshot::Receiver<F>,
}

impl<F> Future for JoinHandle<F> {
  type Output = Result<F, JoinError>;

  fn poll(
    mut self: core::pin::Pin<&mut Self>,
    cx: &mut core::task::Context<'_>,
  ) -> core::task::Poll<Self::Output> {
    core::pin::Pin::new(&mut self.rx)
      .poll(cx)
      .map(|res| res.map_err(|_| JoinError::new()))
  }
}

impl<F> JoinHandle<F> {
  /// Detach the future from the spawner.
  #[inline]
  pub fn detach(self) {
    let _ = self.stop_tx.send(false);
  }

  /// Cancel the future.
  #[inline]
  pub fn cancel(self) {
    let _ = self.stop_tx.send(true);
  }
}

impl<O> super::JoinHandle<O> for JoinHandle<O> {
  type JoinError = JoinError;

  fn detach(self) {
    Self::detach(self)
  }

  fn abort(self) {
    self.cancel();
  }
}

impl<O> super::LocalJoinHandle<O> for JoinHandle<O> {
  type JoinError = JoinError;

  fn detach(self) {
    Self::detach(self)
  }
}

/// A [`AsyncSpawner`] that uses the [`wasm-bindgen-futures`] runtime.
///
/// [`wasm-bindgen-futures`]: https://docs.rs/wasm-bindgen-futures
#[derive(Debug, Clone, Copy)]
pub struct WasmSpawner;

impl AsyncSpawner for WasmSpawner {
  type JoinHandle<F>
    = JoinHandle<F>
  where
    F: Send + 'static;

  fn spawn<F>(future: F) -> Self::JoinHandle<F::Output>
  where
    F::Output: Send + 'static,
    F: core::future::Future + Send + 'static,
  {
    <Self as super::AsyncLocalSpawner>::spawn_local(future)
  }
}

impl AsyncLocalSpawner for WasmSpawner {
  type JoinHandle<F>
    = JoinHandle<F>
  where
    F: 'static;

  fn spawn_local<F>(future: F) -> Self::JoinHandle<F::Output>
  where
    F::Output: 'static,
    F: core::future::Future + 'static,
  {
    use futures_util::FutureExt;

    let (tx, rx) = oneshot::channel();
    let (stop_tx, stop_rx) = oneshot::channel();
    wasm::spawn_local(async {
      futures_util::pin_mut!(future);

      futures_util::select! {
        sig = stop_rx.fuse() => {
          match sig {
            Ok(true) => {
              // if we receive a stop signal, we just stop this task.
            },
            Ok(false) | Err(_) => {
              let _ = future.await;
            },
          }
        },
        future = (&mut future).fuse() => {
          let _ = tx.send(future);
        }
      }
    });
    JoinHandle { stop_tx, rx }
  }
}

impl AsyncBlockingSpawner for WasmSpawner {
  type JoinHandle<R>
    = JoinHandle<R>
  where
    R: Send + 'static;

  fn spawn_blocking<F, R>(_: F) -> Self::JoinHandle<R>
  where
    F: FnOnce() -> R + Send + 'static,
    R: Send + 'static,
  {
    panic!("wasm-bindgen-futures does not support blocking tasks")
  }
}

impl Yielder for WasmSpawner {
  async fn yield_now() {
    YieldNow(false).await
  }

  async fn yield_now_local() {
    YieldNow(false).await
  }
}

/// Future for the [`yield_now`](RuntimeLite::yield_now) function.
#[derive(Debug)]
#[must_use = "futures do nothing unless you `.await` or poll them"]
struct YieldNow(bool);

impl Future for YieldNow {
  type Output = ();

  fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
    if !self.0 {
      self.0 = true;
      cx.waker().wake_by_ref();
      Poll::Pending
    } else {
      Poll::Ready(())
    }
  }
}

/// Concrete [`RuntimeLite`](crate::RuntimeLite) implementation based on [`wasm-bindgen-futures`] runtime.
///
/// [`wasm-bindgen-futures`]: https://docs.rs/wasm-bindgen-futures
#[derive(Debug, Clone, Copy)]
pub struct WasmRuntime;

impl core::fmt::Display for WasmRuntime {
  fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
    write!(f, "wasm-bindgen-futures")
  }
}

impl super::RuntimeLite for WasmRuntime {
  type Spawner = WasmSpawner;
  type LocalSpawner = WasmSpawner;
  type BlockingSpawner = WasmSpawner;

  cfg_time!(
    type Instant = Instant;
    type AfterSpawner = WasmSpawner;

    type Interval = WasmInterval;

    type LocalInterval = WasmInterval;

    type Sleep = WasmSleep;

    type LocalSleep = WasmSleep;

    type Delay<F>
      = WasmDelay<F>
    where
      F: Future + Send;

    type LocalDelay<F>
      = WasmDelay<F>
    where
      F: Future;

    type Timeout<F>
      = WasmTimeout<F>
    where
      F: Future + Send;

    type LocalTimeout<F>
      = WasmTimeout<F>
    where
      F: Future;
  );

  fn new() -> Self {
    Self
  }

  fn name() -> &'static str {
    "wasm-bindgen-futures"
  }

  fn fqname() -> &'static str {
    "wasm-bindgen-futures"
  }

  fn block_on<F: Future>(_f: F) -> F::Output {
    panic!("RuntimeLite::block_on is not supported on wasm")
  }

  async fn yield_now() {
    YieldNow(false).await
  }

  cfg_time!(
    fn interval(interval: Duration) -> Self::Interval {
      use crate::time::AsyncIntervalExt;

      WasmInterval::interval(interval)
    }

    fn interval_at(start: Instant, period: Duration) -> Self::Interval {
      use crate::time::AsyncIntervalExt;

      WasmInterval::interval_at(start, period)
    }

    fn interval_local(interval: Duration) -> Self::LocalInterval {
      use crate::time::AsyncIntervalExt;

      WasmInterval::interval(interval)
    }

    fn interval_local_at(start: Instant, period: Duration) -> Self::LocalInterval {
      use crate::time::AsyncIntervalExt;

      WasmInterval::interval_at(start, period)
    }

    fn sleep(duration: Duration) -> Self::Sleep {
      use crate::time::AsyncSleepExt;

      WasmSleep::sleep(duration)
    }

    fn sleep_until(instant: Instant) -> Self::Sleep {
      use crate::time::AsyncSleepExt;

      WasmSleep::sleep_until(instant)
    }

    fn sleep_local(duration: Duration) -> Self::LocalSleep {
      use crate::time::AsyncSleepExt;

      WasmSleep::sleep(duration)
    }

    fn sleep_local_until(instant: Instant) -> Self::LocalSleep {
      use crate::time::AsyncSleepExt;

      WasmSleep::sleep_until(instant)
    }

    fn delay<F>(duration: Duration, fut: F) -> Self::Delay<F>
    where
      F: Future + Send,
    {
      use crate::time::AsyncDelayExt;

      <WasmDelay<F> as AsyncDelayExt<F>>::delay(duration, fut)
    }

    fn delay_local<F>(duration: Duration, fut: F) -> Self::LocalDelay<F>
    where
      F: Future,
    {
      use crate::time::AsyncLocalDelayExt;

      <WasmDelay<F> as AsyncLocalDelayExt<F>>::delay(duration, fut)
    }

    fn delay_at<F>(deadline: Instant, fut: F) -> Self::Delay<F>
    where
      F: Future + Send,
    {
      use crate::time::AsyncDelayExt;

      <WasmDelay<F> as AsyncDelayExt<F>>::delay_at(deadline, fut)
    }

    fn delay_local_at<F>(deadline: Instant, fut: F) -> Self::LocalDelay<F>
    where
      F: Future,
    {
      use crate::time::AsyncLocalDelayExt;

      <WasmDelay<F> as AsyncLocalDelayExt<F>>::delay_at(deadline, fut)
    }

    fn timeout<F>(duration: Duration, future: F) -> Self::Timeout<F>
    where
      F: Future + Send,
    {
      use crate::time::AsyncTimeout;

      <WasmTimeout<F> as AsyncTimeout<F>>::timeout(duration, future)
    }

    fn timeout_at<F>(deadline: Instant, future: F) -> Self::Timeout<F>
    where
      F: Future + Send,
    {
      use crate::time::AsyncTimeout;

      <WasmTimeout<F> as AsyncTimeout<F>>::timeout_at(deadline, future)
    }

    fn timeout_local<F>(duration: Duration, future: F) -> Self::LocalTimeout<F>
    where
      F: Future,
    {
      use crate::time::AsyncLocalTimeout;

      <WasmTimeout<F> as AsyncLocalTimeout<F>>::timeout_local(duration, future)
    }

    fn timeout_local_at<F>(deadline: Instant, future: F) -> Self::LocalTimeout<F>
    where
      F: Future,
    {
      use crate::time::AsyncLocalTimeout;

      <WasmTimeout<F> as AsyncLocalTimeout<F>>::timeout_local_at(deadline, future)
    }
  );
}