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use parking_lot::Mutex; use std::{ fmt, future::Future, pin::Pin, sync::{ mpsc::{sync_channel, Receiver, SyncSender}, Arc, }, task::{Context, Poll, Waker}, }; #[must_use = "PinkySwear should be used or you can miss errors"] pub struct PinkySwear<T, S = ()> { recv: Receiver<T>, send: SyncSender<T>, inner: Arc<Mutex<Inner<T, S>>>, } #[derive(Clone)] pub struct Pinky<T, S = ()> { send: SyncSender<T>, inner: Arc<Mutex<Inner<T, S>>>, } struct Inner<T, S> { task: Vec<Box<dyn NotifyReady + Send>>, barrier: Option<(Box<dyn Promise<S> + Send>, Box<dyn Fn(S) -> T + Send>)>, before: Option<Box<dyn Promise<S> + Send>>, } impl<T, S> Default for Inner<T, S> { fn default() -> Self { Self { task: Vec::default(), barrier: None, before: None, } } } impl<T: Send + 'static, S: 'static> PinkySwear<T, S> { pub fn new() -> (Self, Pinky<T, S>) { let promise = Self::new_with_inner(Inner::default()); let pinky = promise.pinky(); (promise, pinky) } pub fn after<B: 'static>(promise: PinkySwear<S, B>) -> (Self, Pinky<T, S>) where S: Send { let inner = Inner { task: Vec::default(), barrier: None, before: Some(Box::new(promise)), }; let promise = Self::new_with_inner(inner); let pinky = promise.pinky(); (promise, pinky) } fn new_with_inner(inner: Inner<T, S>) -> Self { let (send, recv) = sync_channel(1); Self { recv, send, inner: Arc::new(Mutex::new(inner)), } } pub fn new_with_data(data: T) -> Self { let (promise, pinky) = Self::new(); pinky.swear(data); promise } fn pinky(&self) -> Pinky<T, S> { Pinky { send: self.send.clone(), inner: self.inner.clone(), } } pub fn try_wait(&self) -> Option<T> { let mut inner = self.inner.lock(); if let Some(before) = inner.before.as_ref() { if let Some(_) = before.try_wait() { inner.before = None; } } if let Some((barrier, transform)) = inner.barrier.as_ref() { barrier.try_wait().map(transform) } else { self.recv.try_recv().ok() } } pub fn wait(&self) -> T { let mut inner = self.inner.lock(); if let Some(before) = inner.before.take() { before.wait(); } if let Some((barrier, transform)) = inner.barrier.as_ref() { transform(barrier.wait()) } else { self.recv.recv().unwrap() } } pub fn subscribe(&self, task: Box<dyn NotifyReady + Send>) { self.inner.lock().task.push(task); } pub fn has_subscriber(&self) -> bool { !self.inner.lock().task.is_empty() } pub fn traverse<F: Send + 'static>( self, transform: Box<dyn Fn(T) -> F + Send>, ) -> PinkySwear<F, T> { let inner = Inner { task: Vec::default(), barrier: Some((Box::new(self), transform)), before: None, }; PinkySwear::new_with_inner(inner) } } impl<T, S> Pinky<T, S> { pub fn swear(&self, data: T) { let _ = self.send.send(data); for task in self.inner.lock().task.iter() { task.notify(); } } } impl<T, S> fmt::Debug for PinkySwear<T, S> { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { write!(f, "PinkySwear") } } impl<T, S> fmt::Debug for Pinky<T, S> { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { write!(f, "Pinky") } } impl<T: Send + 'static, S: 'static> Future for PinkySwear<T, S> { type Output = T; fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> { if !self.has_subscriber() { self.subscribe(Box::new(cx.waker().clone())); } self.try_wait().map(Poll::Ready).unwrap_or(Poll::Pending) } } trait Promise<T> { fn try_wait(&self) -> Option<T>; fn wait(&self) -> T; } impl<T: Send + 'static, S: 'static> Promise<T> for PinkySwear<T, S> { fn try_wait(&self) -> Option<T> { self.try_wait() } fn wait(&self) -> T { self.wait() } } pub trait Cancellable<E> { fn cancel(&self, err: E); } impl<T, S, E> Cancellable<E> for Pinky<Result<T, E>, S> { fn cancel(&self, err: E) { self.swear(Err(err)) } } pub trait NotifyReady { fn notify(&self); } impl NotifyReady for Waker { fn notify(&self) { self.wake_by_ref(); } }