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use std::{ collections::VecDeque, sync::{Arc, atomic::{AtomicUsize, Ordering}}, }; use std::sync::{Condvar, Mutex}; pub trait Msg: Send + 'static {} impl<T: Send + 'static> Msg for T {} #[derive(Copy, Clone, Debug)] pub enum SendError { Disconnected, } #[derive(Copy, Clone, Debug)] pub enum RecvError { Empty, Disconnected, } struct Queue<T: Msg> { inner: VecDeque<T>, } struct Shared<T: Msg> { queue: spin::Mutex<Queue<T>>, disconnected: Mutex<bool>, trigger: Condvar, senders: AtomicUsize, listen_mode: AtomicUsize, } impl<T: Msg> Shared<T> { fn send(&self, msg: T) -> Result<(), SendError> { self.queue.lock().inner.push_back(msg); match self.listen_mode.load(Ordering::Relaxed) { 2 => self.trigger.notify_all(), 1 => {}, 0 => return Err(SendError::Disconnected), _ => unreachable!(), } Ok(()) } fn disconnect(&self) { *self.disconnected.lock().unwrap() = true; self.trigger.notify_all(); } fn wait(&self) { self.listen_mode.fetch_add(1, Ordering::Relaxed); { let disconnected = self.disconnected.lock().unwrap(); if !*disconnected { let _ = self.trigger.wait(disconnected).unwrap(); } } self.listen_mode.fetch_sub(1, Ordering::Relaxed); } fn try_recv(&self) -> Result<T, RecvError> { match self.queue.lock().inner.pop_front() { Some(msg) => Ok(msg), None if *self.disconnected.lock().unwrap() => Err(RecvError::Disconnected), None => Err(RecvError::Empty), } } fn try_recv_all(&self) -> Result<VecDeque<T>, RecvError> { let disconnected = *self.disconnected.lock().unwrap(); let msgs = { let mut msgs = VecDeque::new(); std::mem::swap(&mut msgs, &mut self.queue.lock().inner); msgs }; if msgs.len() == 0 { if disconnected { Err(RecvError::Disconnected) } else { Err(RecvError::Empty) } } else { Ok(msgs) } } fn recv(&self) -> Result<T, RecvError> { loop { match self.try_recv() { Ok(msg) => return Ok(msg), Err(RecvError::Empty) => {}, Err(err) => return Err(err), } self.wait(); } } } pub struct Sender<T: Msg> { shared: Arc<Shared<T>>, } impl<T: Msg> Sender<T> { pub fn send(&self, msg: T) -> Result<(), SendError> { self.shared.send(msg) } } impl<T: Msg> Clone for Sender<T> { fn clone(&self) -> Self { self.shared.senders.fetch_add(1, Ordering::Relaxed); Self { shared: self.shared.clone() } } } impl<T: Msg> Drop for Sender<T> { fn drop(&mut self) { if self.shared.senders.fetch_sub(1, Ordering::Relaxed) == 1 { self.shared.disconnect(); } } } pub struct Receiver<T: Msg> { shared: Arc<Shared<T>>, } impl<T: Msg> Receiver<T> { pub fn recv(&self) -> Result<T, RecvError> { self.shared.recv() } pub fn try_recv(&self) -> Result<T, RecvError> { self.shared.try_recv() } pub fn iter(&self) -> impl Iterator<Item=T> + '_ { Iter { shared: &self.shared, ready: VecDeque::new(), } } pub fn try_iter(&self) -> impl Iterator<Item=T> + '_ { TryIter { shared: &self.shared, ready: VecDeque::new(), } } } impl<T: Msg> Drop for Receiver<T> { fn drop(&mut self) { self.shared.listen_mode.fetch_sub(1, Ordering::Relaxed); } } pub struct Iter<'a, T: Msg> { shared: &'a Shared<T>, ready: VecDeque<T>, } impl<'a, T: Msg> Iterator for Iter<'a, T> { type Item = T; fn next(&mut self) -> Option<Self::Item> { while self.ready.len() == 0 { self.ready = match self.shared.try_recv_all() { Ok(msgs) => msgs, Err(RecvError::Empty) => { self.shared.wait(); continue }, Err(RecvError::Disconnected) => break, }; } self.ready.pop_front() } } pub struct TryIter<'a, T: Msg> { shared: &'a Shared<T>, ready: VecDeque<T>, } impl<'a, T: Msg> Iterator for TryIter<'a, T> { type Item = T; fn next(&mut self) -> Option<Self::Item> { if self.ready.len() == 0 { self.ready = match self.shared.try_recv_all() { Ok(msgs) => msgs, Err(RecvError::Empty) | Err(RecvError::Disconnected) => VecDeque::new(), }; } self.ready.pop_front() } } pub fn channel<T: Msg>() -> (Sender<T>, Receiver<T>) { let shared = Arc::new(Shared { queue: spin::Mutex::new(Queue { inner: VecDeque::new(), }), disconnected: Mutex::new(false), trigger: Condvar::new(), senders: AtomicUsize::new(1), listen_mode: AtomicUsize::new(1), }); ( Sender { shared: shared.clone() }, Receiver { shared }, ) }