use core::{ pin::Pin, future::Future, sync::atomic::{AtomicPtr, AtomicUsize, Ordering}, task::{Context, Poll}, }; use alloc::boxed::Box; use super::{spin_lock_yield, notify_spin_lock}; pub struct Sender<'a, T> where T: Clone { list: &'a [AtomicPtr], write: &'a AtomicUsize, read: &'a AtomicUsize, } pub struct Receiver<'a, T> where T: Clone { list: &'a [AtomicPtr], write: &'a AtomicUsize, read: &'a AtomicUsize, } impl<'a, T> Sender<'a, T> where T: Clone { pub const fn new(list: &'static [AtomicPtr], write: &'static AtomicUsize, read: &'static AtomicUsize) -> Self { Sender {list, write, read} } pub fn try_send>>(&mut self, content: B) -> Result<(), B> { let write = self.write.load(Ordering::Relaxed); if (write + 1) % self.list.len() == self.read.load(Ordering::Acquire) { Err(content) } else { let ptr = Box::into_raw(content.into()); let entry = &self.list[write]; let prev = entry.swap(ptr, Ordering::Relaxed); // we allow other end get it first self.write.store((write + 1) % self.list.len(), Ordering::Release); notify_spin_lock(); if !prev.is_null() { unsafe { Box::from_raw(prev); } } Ok(()) } } pub fn send>>(&mut self, content: B) { let mut content = content; while let Err(back) = self.try_send(content) { content = back; spin_lock_yield(); } } pub async fn async_send>>(&mut self, content: B) { struct Send<'a, 'b, T> where T: Clone, 'b: 'a { sender: &'a mut Sender<'b, T>, content: Result<(), Box>, } impl Future for Send<'_, '_, T> where T: Clone { type Output = (); fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll { match core::mem::replace(&mut self.content, Ok(())) { Err(content) => { if let Err(content) = self.sender.try_send(content) { // failure self.content = Err(content); cx.waker().wake_by_ref(); Poll::Pending } else { // success Poll::Ready(()) } } Ok(_) => panic!("Send future polled after success"), } } } Send { sender: self, content: Err(content.into()), }.await } /// free all items in the queue. It is the user's responsibility to /// ensure no reader is trying to copy the data. pub unsafe fn drop_elements(&mut self) { for v in self.list.iter() { let original = v.swap(core::ptr::null_mut(), Ordering::Relaxed); if !original.is_null() { Box::from_raw(original); } } } /// Reset the `sync_channel`, *forget* all items in the queue. Affects both the sender and /// receiver. pub unsafe fn reset(&mut self) { self.write.store(0, Ordering::Relaxed); self.read.store(0, Ordering::Relaxed); for v in self.list.iter() { v.store(core::ptr::null_mut(), Ordering::Relaxed); } } } impl<'a, T> Receiver<'a, T> where T: Clone { pub const fn new(list: &'static [AtomicPtr], write: &'static AtomicUsize, read: &'static AtomicUsize) -> Self { Receiver {list, write, read} } pub fn try_recv(&mut self) -> Result { let read = self.read.load(Ordering::Relaxed); if read == self.write.load(Ordering::Acquire) { Err(()) } else { let entry = &self.list[read]; let data = unsafe { // we cannot deallocate the box Box::leak(Box::from_raw(entry.load(Ordering::Relaxed))) }; let result = data.clone(); self.read.store((read + 1) % self.list.len(), Ordering::Release); notify_spin_lock(); Ok(result) } } pub fn recv(&mut self) -> T { loop { if let Ok(data) = self.try_recv() { return data; } spin_lock_yield(); } } pub async fn async_recv(&mut self) -> T { struct Recv<'a, 'b, T> where T: Clone, 'b: 'a { receiver: &'a mut Receiver<'b, T>, } impl Future for Recv<'_, '_, T> where T: Clone { type Output = T; fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll { if let Ok(content) = self.receiver.try_recv() { Poll::Ready(content) } else { cx.waker().wake_by_ref(); Poll::Pending } } } Recv { receiver: self, }.await } } impl<'a, T> Iterator for Receiver<'a, T> where T: Clone { type Item = T; fn next(&mut self) -> Option { Some(self.recv()) } } #[macro_export] /// Macro for initializing the sync_channel with static buffer and indexes. /// Note that this requires `#![feature(const_in_array_repeat_expressions)]` macro_rules! sync_channel { ($t: ty, $cap: expr) => { { use core::sync::atomic::{AtomicUsize, AtomicPtr}; use $crate::sync_channel::{Sender, Receiver}; static LIST: [AtomicPtr<$t>; $cap + 1] = [AtomicPtr::new(core::ptr::null_mut()); $cap + 1]; static WRITE: AtomicUsize = AtomicUsize::new(0); static READ: AtomicUsize = AtomicUsize::new(0); (Sender::new(&LIST, &WRITE, &READ), Receiver::new(&LIST, &WRITE, &READ)) } }; }