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zynq-rs/libcortex_a9/src/sync_channel.rs

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use core::{
pin::Pin,
future::Future,
sync::atomic::{AtomicPtr, AtomicUsize, Ordering},
task::{Context, Poll},
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};
use alloc::boxed::Box;
use super::{spin_lock_yield, notify_spin_lock};
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pub struct Sender<'a, T> where T: Clone {
list: &'a [AtomicPtr<T>],
write: &'a AtomicUsize,
read: &'a AtomicUsize,
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}
pub struct Receiver<'a, T> where T: Clone {
list: &'a [AtomicPtr<T>],
write: &'a AtomicUsize,
read: &'a AtomicUsize,
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}
impl<'a, T> Sender<'a, T> where T: Clone {
pub const fn new(list: &'static [AtomicPtr<T>], write: &'static AtomicUsize, read: &'static AtomicUsize) -> Self {
Sender {list, write, read}
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}
pub fn try_send<B: Into<Box<T>>>(&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<B: Into<Box<T>>>(&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<B: Into<Box<T>>>(&mut self, content: B) {
struct Send<'a, 'b, T> where T: Clone, 'b: 'a {
sender: &'a mut Sender<'b, T>,
content: Result<(), Box<T>>,
}
impl<T> Future for Send<'_, '_, T> where T: Clone {
type Output = ();
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
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);
}
}
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}
impl<'a, T> Receiver<'a, T> where T: Clone {
pub const fn new(list: &'static [AtomicPtr<T>], write: &'static AtomicUsize, read: &'static AtomicUsize) -> Self {
Receiver {list, write, read}
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}
pub fn try_recv(&mut self) -> Result<T, ()> {
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<T> Future for Recv<'_, '_, T> where T: Clone {
type Output = T;
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
if let Ok(content) = self.receiver.try_recv() {
Poll::Ready(content)
} else {
cx.waker().wake_by_ref();
Poll::Pending
}
}
}
Recv {
receiver: self,
}.await
}
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}
impl<'a, T> Iterator for Receiver<'a, T> where T: Clone {
type Item = T;
fn next(&mut self) -> Option<Self::Item> {
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))
}
};
}