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Cell or UnsafeCell?
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@futursolo
futursolo committed Aug 14, 2022
1 parent 24bbea2 commit a8ee1c0
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Showing 2 changed files with 27 additions and 49 deletions.
44 changes: 18 additions & 26 deletions packages/yew/src/platform/pinned/mpsc.rs
View file
@@ -1,5 +1,6 @@
//! A multi-producer single-receiver channel.

use std::cell::UnsafeCell;
use std::collections::VecDeque;
use std::marker::PhantomData;
use std::rc::Rc;
Expand Down Expand Up @@ -40,19 +41,6 @@ struct Inner<T> {
}

impl<T> Inner<T> {
/// Creates a unchecked mutable reference from an immutable reference.
///
/// SAFETY: You can only use this when:
///
/// 1. The mutable reference is released at the end of a function call.
/// 2. No parent function has acquired the mutable reference.
/// 3. The caller is not an async function / the mutable reference is released before an await
/// statement.
#[inline]
unsafe fn get_mut_unchecked(&self) -> *mut Self {
self as *const Self as *mut Self
}

fn close(&mut self) {
self.closed = true;

Expand All @@ -65,7 +53,7 @@ impl<T> Inner<T> {
/// The receiver of an unbounded mpsc channel.
#[derive(Debug)]
pub struct UnboundedReceiver<T> {
inner: Rc<Inner<T>>,
inner: Rc<UnsafeCell<Inner<T>>>,
}

impl<T> UnboundedReceiver<T> {
Expand All @@ -78,7 +66,7 @@ impl<T> UnboundedReceiver<T> {
pub fn try_next(&self) -> std::result::Result<Option<T>, TryRecvError> {
// SAFETY: This function is not used by any other functions and hence uniquely owns the
// mutable reference.
let inner = unsafe { &mut *self.inner.get_mut_unchecked() };
let inner = unsafe { &mut *self.inner.get() };

match (inner.items.pop_front(), inner.closed) {
(Some(m), _) => Ok(Some(m)),
Expand All @@ -99,7 +87,7 @@ impl<T> Stream for UnboundedReceiver<T> {
) -> std::task::Poll<Option<Self::Item>> {
// SAFETY: This function is not used by any other functions and hence uniquely owns the
// mutable reference.
let inner = unsafe { &mut *self.inner.get_mut_unchecked() };
let inner = unsafe { &mut *self.inner.get() };

match (inner.items.pop_front(), inner.closed) {
(Some(m), _) => Poll::Ready(Some(m)),
Expand All @@ -114,31 +102,34 @@ impl<T> Stream for UnboundedReceiver<T> {

impl<T> FusedStream for UnboundedReceiver<T> {
fn is_terminated(&self) -> bool {
self.inner.items.is_empty() && self.inner.closed
// SAFETY: This function is not used by any other functions and hence uniquely owns the
// reference.
let inner = unsafe { &*self.inner.get() };
inner.items.is_empty() && inner.closed
}
}

impl<T> Drop for UnboundedReceiver<T> {
fn drop(&mut self) {
// SAFETY: This function is not used by any other functions and hence uniquely owns the
// mutable reference.
let inner = unsafe { &mut *self.inner.get_mut_unchecked() };
let inner = unsafe { &mut *self.inner.get() };
inner.close();
}
}

/// The sender of an unbounded mpsc channel.
#[derive(Debug)]
pub struct UnboundedSender<T> {
inner: Rc<Inner<T>>,
inner: Rc<UnsafeCell<Inner<T>>>,
}

impl<T> UnboundedSender<T> {
/// Sends a value to the unbounded receiver.
pub fn send_now(&self, item: T) -> Result<(), SendError<T>> {
// SAFETY: This function is not used by any function that have already acquired a mutable
// reference.
let inner = unsafe { &mut *self.inner.get_mut_unchecked() };
let inner = unsafe { &mut *self.inner.get() };

if inner.closed {
return Err(SendError { inner: item });
Expand All @@ -157,7 +148,7 @@ impl<T> UnboundedSender<T> {
pub fn close_now(&self) {
// SAFETY: This function is not used by any other functions that have acquired a mutable
// reference and hence uniquely owns the mutable reference.
let inner = unsafe { &mut *self.inner.get_mut_unchecked() };
let inner = unsafe { &mut *self.inner.get() };
inner.close();
}
}
Expand All @@ -170,7 +161,7 @@ impl<T> Clone for UnboundedSender<T> {

// SAFETY: This function is not used by any other functions and hence uniquely owns the
// mutable reference.
let inner = unsafe { &mut *self.inner.get_mut_unchecked() };
let inner = unsafe { &mut *self.inner.get() };
inner.sender_ctr += 1;

self_
Expand All @@ -181,7 +172,7 @@ impl<T> Drop for UnboundedSender<T> {
fn drop(&mut self) {
// SAFETY: This function is not used by any other functions and hence uniquely owns the
// mutable reference.
let inner = unsafe { &mut *self.inner.get_mut_unchecked() };
let inner = unsafe { &mut *self.inner.get() };

let sender_ctr = {
inner.sender_ctr -= 1;
Expand All @@ -207,7 +198,8 @@ impl<T> Sink<T> for &'_ UnboundedSender<T> {
self: std::pin::Pin<&mut Self>,
_cx: &mut std::task::Context<'_>,
) -> Poll<Result<(), Self::Error>> {
match self.inner.closed {
let inner = unsafe { &*self.inner.get() };
match inner.closed {
false => Poll::Ready(Ok(())),
true => Poll::Ready(Err(TrySendError {
_marker: PhantomData,
Expand Down Expand Up @@ -239,13 +231,13 @@ impl<T> Sink<T> for &'_ UnboundedSender<T> {
/// This channel has an infinite buffer and can run out of memory if the channel is not actively
/// drained.
pub fn unbounded<T>() -> (UnboundedSender<T>, UnboundedReceiver<T>) {
let inner = Rc::new(Inner {
let inner = Rc::new(UnsafeCell::new(Inner {
rx_waker: None,
closed: false,

sender_ctr: 1,
items: VecDeque::new(),
});
}));

(
UnboundedSender {
Expand Down
32 changes: 9 additions & 23 deletions packages/yew/src/platform/pinned/oneshot.rs
View file
@@ -1,5 +1,6 @@
//! A one-time send - receive channel.

use std::cell::UnsafeCell;
use std::future::Future;
use std::marker::PhantomData;
use std::rc::Rc;
Expand All @@ -21,25 +22,10 @@ struct Inner<T> {
item: Option<T>,
}

impl<T> Inner<T> {
/// Creates a unchecked mutable reference from a mutable reference.
///
/// SAFETY: You can only use this when:
///
/// 1. The mutable reference is released at the end of a function call.
/// 2. No parent function has acquired the mutable reference.
/// 3. The caller is not an async function / the mutable reference is released before an await
/// statement.
#[inline]
unsafe fn get_mut_unchecked(&self) -> *mut Self {
self as *const Self as *mut Self
}
}

/// The receiver of a oneshot channel.
#[derive(Debug)]
pub struct Receiver<T> {
inner: Rc<Inner<T>>,
inner: Rc<UnsafeCell<Inner<T>>>,
}

impl<T> Future for Receiver<T> {
Expand All @@ -48,7 +34,7 @@ impl<T> Future for Receiver<T> {
fn poll(self: std::pin::Pin<&mut Self>, cx: &mut std::task::Context<'_>) -> Poll<Self::Output> {
// SAFETY: This function is not used by any other functions and hence uniquely owns the
// mutable reference.
let inner = unsafe { &mut *self.inner.get_mut_unchecked() };
let inner = unsafe { &mut *self.inner.get() };

// Implementation Note:
//
Expand All @@ -74,23 +60,23 @@ impl<T> Drop for Receiver<T> {
fn drop(&mut self) {
// SAFETY: This function is not used by any other functions and hence uniquely owns the
// mutable reference.
let inner = unsafe { &mut *self.inner.get_mut_unchecked() };
let inner = unsafe { &mut *self.inner.get() };
inner.closed = true;
}
}

/// The sender of a oneshot channel.
#[derive(Debug)]
pub struct Sender<T> {
inner: Rc<Inner<T>>,
inner: Rc<UnsafeCell<Inner<T>>>,
}

impl<T> Sender<T> {
/// Send an item to the other side of the channel, consumes the sender.
pub fn send(self, item: T) -> Result<(), T> {
// SAFETY: This function is not used by any other functions and hence uniquely owns the
// mutable reference.
let inner = unsafe { &mut *self.inner.get_mut_unchecked() };
let inner = unsafe { &mut *self.inner.get() };

if inner.closed {
return Err(item);
Expand All @@ -110,7 +96,7 @@ impl<T> Drop for Sender<T> {
fn drop(&mut self) {
// SAFETY: This function is not used by any other functions and hence uniquely owns the
// mutable reference.
let inner = unsafe { &mut *self.inner.get_mut_unchecked() };
let inner = unsafe { &mut *self.inner.get() };

inner.closed = true;

Expand All @@ -124,11 +110,11 @@ impl<T> Drop for Sender<T> {

/// Creates a oneshot channel.
pub fn channel<T>() -> (Sender<T>, Receiver<T>) {
let inner = Rc::new(Inner {
let inner = Rc::new(UnsafeCell::new(Inner {
rx_waker: None,
closed: false,
item: None,
});
}));

(
Sender {
Expand Down

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