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lib.rs
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//! Async broadcast channel
//!
//! An async multi-producer multi-consumer broadcast channel, where each consumer gets a clone of every
//! message sent on the channel. For obvious reasons, the channel can only be used to broadcast types
//! that implement [`Clone`].
//!
//! A channel has the [`Sender`] and [`Receiver`] side. Both sides are cloneable and can be shared
//! among multiple threads.
//!
//! When all `Sender`s or all `Receiver`s are dropped, the channel becomes closed. When a channel is
//! closed, no more messages can be sent, but remaining messages can still be received.
//!
//! The channel can also be closed manually by calling [`Sender::close()`] or [`Receiver::close()`].
//!
//! ## Examples
//!
//! ```rust
//! use async_broadcast::{broadcast, TryRecvError};
//! use futures_lite::{future::block_on, stream::StreamExt};
//!
//! block_on(async move {
//! let (s1, mut r1) = broadcast(2);
//! let s2 = s1.clone();
//! let mut r2 = r1.clone();
//!
//! // Send 2 messages from two different senders.
//! s1.broadcast(7).await.unwrap();
//! s2.broadcast(8).await.unwrap();
//!
//! // Channel is now at capacity so sending more messages will result in an error.
//! assert!(s2.try_broadcast(9).unwrap_err().is_full());
//! assert!(s1.try_broadcast(10).unwrap_err().is_full());
//!
//! // We can use `recv` method of the `Stream` implementation to receive messages.
//! assert_eq!(r1.next().await.unwrap(), 7);
//! assert_eq!(r1.recv().await.unwrap(), 8);
//! assert_eq!(r2.next().await.unwrap(), 7);
//! assert_eq!(r2.recv().await.unwrap(), 8);
//!
//! // All receiver got all messages so channel is now empty.
//! assert_eq!(r1.try_recv(), Err(TryRecvError::Empty));
//! assert_eq!(r2.try_recv(), Err(TryRecvError::Empty));
//!
//! // Drop both senders, which closes the channel.
//! drop(s1);
//! drop(s2);
//!
//! assert_eq!(r1.try_recv(), Err(TryRecvError::Closed));
//! assert_eq!(r2.try_recv(), Err(TryRecvError::Closed));
//! })
//! ```
//!
//! ## Difference with `async-channel`
//!
//! This crate is similar to [`async-channel`] in that they both provide an MPMC channel but the
//! main difference being that in `async-channel`, each message sent on the channel is only received
//! by one of the receivers. `async-broadcast` on the other hand, delivers each message to every
//! receiver (IOW broadcast) by cloning it for each receiver.
//!
//! [`async-channel`]: https://crates.io/crates/async-channel
//!
//! ## Difference with other broadcast crates
//!
//! * [`broadcaster`]: The main difference would be that `broadcaster` doesn't have a sender and
//! receiver split and both sides use clones of the same BroadcastChannel instance. The messages
//! are sent are sent to all channel clones. While this can work for many cases, the lack of
//! sender and receiver split, means that often times, you'll find yourself having to drain the
//! channel on the sending side yourself.
//!
//! * [`postage`]: this crate provides a [broadcast API][pba] similar to `async_broadcast`. However,
//! it:
//! - (at the time of this writing) duplicates [futures] API, which isn't ideal.
//! - Does not support overflow mode nor has the concept of inactive receivers, so a slow or
//! inactive receiver blocking the whole channel is not a solvable problem.
//! - Provides all kinds of channels, which is generally good but if you just need a broadcast
//! channel, `async_broadcast` is probably a better choice.
//!
//! * [`tokio::sync`]: Tokio's `sync` module provides a [broadcast channel][tbc] API. The differences
//! here are:
//! - While this implementation does provide [overflow mode][tom], it is the default behavior and not
//! opt-in.
//! - There is no equivalent of inactive receivers.
//! - While it's possible to build tokio with only the `sync` module, it comes with other APIs that
//! you may not need.
//!
//! [`broadcaster`]: https://crates.io/crates/broadcaster
//! [`postage`]: https://crates.io/crates/postage
//! [pba]: https://docs.rs/postage/0.4.1/postage/broadcast/fn.channel.html
//! [futures]: https://crates.io/crates/futures
//! [`tokio::sync`]: https://docs.rs/tokio/1.6.0/tokio/sync
//! [tbc]: https://docs.rs/tokio/1.6.0/tokio/sync/broadcast/index.html
//! [tom]: https://docs.rs/tokio/1.6.0/tokio/sync/broadcast/index.html#lagging
//!
#![forbid(unsafe_code)]
#![deny(missing_debug_implementations, nonstandard_style, rust_2018_idioms)]
#![warn(rustdoc::missing_doc_code_examples, unreachable_pub)]
#![doc(
html_favicon_url = "https://raw.githubusercontent.com/smol-rs/smol/master/assets/images/logo_fullsize_transparent.png"
)]
#![doc(
html_logo_url = "https://raw.githubusercontent.com/smol-rs/smol/master/assets/images/logo_fullsize_transparent.png"
)]
#[cfg(doctest)]
mod doctests {
doc_comment::doctest!("../README.md");
}
use std::collections::VecDeque;
use std::convert::TryInto;
use std::error;
use std::fmt;
use std::future::Future;
use std::marker::PhantomPinned;
use std::pin::Pin;
use std::sync::{Arc, Mutex};
use std::task::{Context, Poll};
use event_listener::{Event, EventListener};
use event_listener_strategy::{easy_wrapper, EventListenerFuture};
use futures_core::{ready, stream::Stream};
use pin_project_lite::pin_project;
/// Create a new broadcast channel.
///
/// The created channel has space to hold at most `cap` messages at a time.
///
/// # Panics
///
/// Capacity must be a positive number. If `cap` is zero, this function will panic.
///
/// # Examples
///
/// ```
/// # futures_lite::future::block_on(async {
/// use async_broadcast::{broadcast, TryRecvError, TrySendError};
///
/// let (s, mut r1) = broadcast(1);
/// let mut r2 = r1.clone();
///
/// assert_eq!(s.broadcast(10).await, Ok(None));
/// assert_eq!(s.try_broadcast(20), Err(TrySendError::Full(20)));
///
/// assert_eq!(r1.recv().await, Ok(10));
/// assert_eq!(r2.recv().await, Ok(10));
/// assert_eq!(r1.try_recv(), Err(TryRecvError::Empty));
/// assert_eq!(r2.try_recv(), Err(TryRecvError::Empty));
/// # });
/// ```
pub fn broadcast<T>(cap: usize) -> (Sender<T>, Receiver<T>) {
assert!(cap > 0, "capacity cannot be zero");
let inner = Arc::new(Mutex::new(Inner {
queue: VecDeque::with_capacity(cap),
capacity: cap,
overflow: false,
await_active: true,
receiver_count: 1,
inactive_receiver_count: 0,
sender_count: 1,
head_pos: 0,
is_closed: false,
send_ops: Event::new(),
recv_ops: Event::new(),
}));
let s = Sender {
inner: inner.clone(),
};
let r = Receiver {
inner,
pos: 0,
listener: None,
};
(s, r)
}
#[derive(Debug)]
struct Inner<T> {
queue: VecDeque<(T, usize)>,
// We assign the same capacity to the queue but that's just specifying the minimum capacity and
// the actual capacity could be anything. Hence the need to keep track of our own set capacity.
capacity: usize,
receiver_count: usize,
inactive_receiver_count: usize,
sender_count: usize,
/// Send sequence number of the front of the queue
head_pos: u64,
overflow: bool,
await_active: bool,
is_closed: bool,
/// Send operations waiting while the channel is full.
send_ops: Event,
/// Receive operations waiting while the channel is empty and not closed.
recv_ops: Event,
}
impl<T> Inner<T> {
/// Try receiving at the given position, returning either the element or a reference to it.
///
/// Result is used here instead of Cow because we don't have a Clone bound on T.
fn try_recv_at(&mut self, pos: &mut u64) -> Result<Result<T, &T>, TryRecvError> {
let i = match pos.checked_sub(self.head_pos) {
Some(i) => i
.try_into()
.expect("Head position more than usize::MAX behind a receiver"),
None => {
let count = self.head_pos - *pos;
*pos = self.head_pos;
return Err(TryRecvError::Overflowed(count));
}
};
let last_waiter;
if let Some((_elt, waiters)) = self.queue.get_mut(i) {
*pos += 1;
*waiters -= 1;
last_waiter = *waiters == 0;
} else {
debug_assert_eq!(i, self.queue.len());
if self.is_closed {
return Err(TryRecvError::Closed);
} else {
return Err(TryRecvError::Empty);
}
}
// If we read from the front of the queue and this is the last receiver reading it
// we can pop the queue instead of cloning the message
if last_waiter {
// Only the first element of the queue should have 0 waiters
assert_eq!(i, 0);
// Remove the element from the queue, adjust space, and notify senders
let elt = self.queue.pop_front().unwrap().0;
self.head_pos += 1;
if !self.overflow {
// Notify 1 awaiting senders that there is now room. If there is still room in the
// queue, the notified operation will notify another awaiting sender.
self.send_ops.notify(1);
}
Ok(Ok(elt))
} else {
Ok(Err(&self.queue[i].0))
}
}
/// Closes the channel and notifies all waiting operations.
///
/// Returns `true` if this call has closed the channel and it was not closed already.
fn close(&mut self) -> bool {
if self.is_closed {
return false;
}
self.is_closed = true;
// Notify all waiting senders and receivers.
self.send_ops.notify(usize::MAX);
self.recv_ops.notify(usize::MAX);
true
}
/// Set the channel capacity.
///
/// There are times when you need to change the channel's capacity after creating it. If the
/// `new_cap` is less than the number of messages in the channel, the oldest messages will be
/// dropped to shrink the channel.
fn set_capacity(&mut self, new_cap: usize) {
self.capacity = new_cap;
if new_cap > self.queue.capacity() {
let diff = new_cap - self.queue.capacity();
self.queue.reserve(diff);
}
// Ensure queue doesn't have more than `new_cap` messages.
if new_cap < self.queue.len() {
let diff = self.queue.len() - new_cap;
self.queue.drain(0..diff);
self.head_pos += diff as u64;
}
}
/// Close the channel if there aren't any receivers present anymore
fn close_channel(&mut self) {
if self.receiver_count == 0 && self.inactive_receiver_count == 0 {
self.close();
}
}
}
/// The sending side of the broadcast channel.
///
/// Senders can be cloned and shared among threads. When all senders associated with a channel are
/// dropped, the channel becomes closed.
///
/// The channel can also be closed manually by calling [`Sender::close()`].
#[derive(Debug)]
pub struct Sender<T> {
inner: Arc<Mutex<Inner<T>>>,
}
impl<T> Sender<T> {
/// Returns the channel capacity.
///
/// # Examples
///
/// ```
/// use async_broadcast::broadcast;
///
/// let (s, r) = broadcast::<i32>(5);
/// assert_eq!(s.capacity(), 5);
/// ```
pub fn capacity(&self) -> usize {
self.inner.lock().unwrap().capacity
}
/// Set the channel capacity.
///
/// There are times when you need to change the channel's capacity after creating it. If the
/// `new_cap` is less than the number of messages in the channel, the oldest messages will be
/// dropped to shrink the channel.
///
/// # Examples
///
/// ```
/// use async_broadcast::{broadcast, TrySendError, TryRecvError};
///
/// let (mut s, mut r) = broadcast::<i32>(3);
/// assert_eq!(s.capacity(), 3);
/// s.try_broadcast(1).unwrap();
/// s.try_broadcast(2).unwrap();
/// s.try_broadcast(3).unwrap();
///
/// s.set_capacity(1);
/// assert_eq!(s.capacity(), 1);
/// assert_eq!(r.try_recv(), Err(TryRecvError::Overflowed(2)));
/// assert_eq!(r.try_recv().unwrap(), 3);
/// assert_eq!(r.try_recv(), Err(TryRecvError::Empty));
/// s.try_broadcast(1).unwrap();
/// assert_eq!(s.try_broadcast(2), Err(TrySendError::Full(2)));
///
/// s.set_capacity(2);
/// assert_eq!(s.capacity(), 2);
/// s.try_broadcast(2).unwrap();
/// assert_eq!(s.try_broadcast(2), Err(TrySendError::Full(2)));
/// ```
pub fn set_capacity(&mut self, new_cap: usize) {
self.inner.lock().unwrap().set_capacity(new_cap);
}
/// If overflow mode is enabled on this channel.
///
/// # Examples
///
/// ```
/// use async_broadcast::broadcast;
///
/// let (s, r) = broadcast::<i32>(5);
/// assert!(!s.overflow());
/// ```
pub fn overflow(&self) -> bool {
self.inner.lock().unwrap().overflow
}
/// Set overflow mode on the channel.
///
/// When overflow mode is set, broadcasting to the channel will succeed even if the channel is
/// full. It achieves that by removing the oldest message from the channel.
///
/// # Examples
///
/// ```
/// use async_broadcast::{broadcast, TrySendError, TryRecvError};
///
/// let (mut s, mut r) = broadcast::<i32>(2);
/// s.try_broadcast(1).unwrap();
/// s.try_broadcast(2).unwrap();
/// assert_eq!(s.try_broadcast(3), Err(TrySendError::Full(3)));
/// s.set_overflow(true);
/// assert_eq!(s.try_broadcast(3).unwrap(), Some(1));
/// assert_eq!(s.try_broadcast(4).unwrap(), Some(2));
///
/// assert_eq!(r.try_recv(), Err(TryRecvError::Overflowed(2)));
/// assert_eq!(r.try_recv().unwrap(), 3);
/// assert_eq!(r.try_recv().unwrap(), 4);
/// assert_eq!(r.try_recv(), Err(TryRecvError::Empty));
/// ```
pub fn set_overflow(&mut self, overflow: bool) {
self.inner.lock().unwrap().overflow = overflow;
}
/// If sender will wait for active receivers.
///
/// If set to `false`, [`Send`] will resolve immediately with a [`SendError`]. Defaults to
/// `true`.
///
/// # Examples
///
/// ```
/// use async_broadcast::broadcast;
///
/// let (s, _) = broadcast::<i32>(5);
/// assert!(s.await_active());
/// ```
pub fn await_active(&self) -> bool {
self.inner.lock().unwrap().await_active
}
/// Specify if sender will wait for active receivers.
///
/// If set to `false`, [`Send`] will resolve immediately with a [`SendError`]. Defaults to
/// `true`.
///
/// # Examples
///
/// ```
/// # futures_lite::future::block_on(async {
/// use async_broadcast::broadcast;
///
/// let (mut s, mut r) = broadcast::<i32>(2);
/// s.broadcast(1).await.unwrap();
///
/// let _ = r.deactivate();
/// s.set_await_active(false);
/// assert!(s.broadcast(2).await.is_err());
/// # });
/// ```
pub fn set_await_active(&mut self, await_active: bool) {
self.inner.lock().unwrap().await_active = await_active;
}
/// Closes the channel.
///
/// Returns `true` if this call has closed the channel and it was not closed already.
///
/// The remaining messages can still be received.
///
/// # Examples
///
/// ```
/// # futures_lite::future::block_on(async {
/// use async_broadcast::{broadcast, RecvError};
///
/// let (s, mut r) = broadcast(1);
/// s.broadcast(1).await.unwrap();
/// assert!(s.close());
///
/// assert_eq!(r.recv().await.unwrap(), 1);
/// assert_eq!(r.recv().await, Err(RecvError::Closed));
/// # });
/// ```
pub fn close(&self) -> bool {
self.inner.lock().unwrap().close()
}
/// Returns `true` if the channel is closed.
///
/// # Examples
///
/// ```
/// # futures_lite::future::block_on(async {
/// use async_broadcast::{broadcast, RecvError};
///
/// let (s, r) = broadcast::<()>(1);
/// assert!(!s.is_closed());
///
/// drop(r);
/// assert!(s.is_closed());
/// # });
/// ```
pub fn is_closed(&self) -> bool {
self.inner.lock().unwrap().is_closed
}
/// Returns `true` if the channel is empty.
///
/// # Examples
///
/// ```
/// # futures_lite::future::block_on(async {
/// use async_broadcast::broadcast;
///
/// let (s, r) = broadcast(1);
///
/// assert!(s.is_empty());
/// s.broadcast(1).await;
/// assert!(!s.is_empty());
/// # });
/// ```
pub fn is_empty(&self) -> bool {
self.inner.lock().unwrap().queue.is_empty()
}
/// Returns `true` if the channel is full.
///
/// # Examples
///
/// ```
/// # futures_lite::future::block_on(async {
/// use async_broadcast::broadcast;
///
/// let (s, r) = broadcast(1);
///
/// assert!(!s.is_full());
/// s.broadcast(1).await;
/// assert!(s.is_full());
/// # });
/// ```
pub fn is_full(&self) -> bool {
let inner = self.inner.lock().unwrap();
inner.queue.len() == inner.capacity
}
/// Returns the number of messages in the channel.
///
/// # Examples
///
/// ```
/// # futures_lite::future::block_on(async {
/// use async_broadcast::broadcast;
///
/// let (s, r) = broadcast(2);
/// assert_eq!(s.len(), 0);
///
/// s.broadcast(1).await;
/// s.broadcast(2).await;
/// assert_eq!(s.len(), 2);
/// # });
/// ```
pub fn len(&self) -> usize {
self.inner.lock().unwrap().queue.len()
}
/// Returns the number of receivers for the channel.
///
/// This does not include inactive receivers. Use [`Sender::inactive_receiver_count`] if you
/// are interested in that.
///
/// # Examples
///
/// ```
/// use async_broadcast::broadcast;
///
/// let (s, r) = broadcast::<()>(1);
/// assert_eq!(s.receiver_count(), 1);
/// let r = r.deactivate();
/// assert_eq!(s.receiver_count(), 0);
///
/// let r2 = r.activate_cloned();
/// assert_eq!(r.receiver_count(), 1);
/// assert_eq!(r.inactive_receiver_count(), 1);
/// ```
pub fn receiver_count(&self) -> usize {
self.inner.lock().unwrap().receiver_count
}
/// Returns the number of inactive receivers for the channel.
///
/// # Examples
///
/// ```
/// use async_broadcast::broadcast;
///
/// let (s, r) = broadcast::<()>(1);
/// assert_eq!(s.receiver_count(), 1);
/// let r = r.deactivate();
/// assert_eq!(s.receiver_count(), 0);
///
/// let r2 = r.activate_cloned();
/// assert_eq!(r.receiver_count(), 1);
/// assert_eq!(r.inactive_receiver_count(), 1);
/// ```
pub fn inactive_receiver_count(&self) -> usize {
self.inner.lock().unwrap().inactive_receiver_count
}
/// Returns the number of senders for the channel.
///
/// # Examples
///
/// ```
/// # futures_lite::future::block_on(async {
/// use async_broadcast::broadcast;
///
/// let (s, r) = broadcast::<()>(1);
/// assert_eq!(s.sender_count(), 1);
///
/// let s2 = s.clone();
/// assert_eq!(s.sender_count(), 2);
/// # });
/// ```
pub fn sender_count(&self) -> usize {
self.inner.lock().unwrap().sender_count
}
/// Produce a new Receiver for this channel.
///
/// The new receiver starts with zero messages available. This will not re-open the channel if
/// it was closed due to all receivers being dropped.
///
/// # Examples
///
/// ```
/// # futures_lite::future::block_on(async {
/// use async_broadcast::{broadcast, RecvError};
///
/// let (s, mut r1) = broadcast(2);
///
/// assert_eq!(s.broadcast(1).await, Ok(None));
///
/// let mut r2 = s.new_receiver();
///
/// assert_eq!(s.broadcast(2).await, Ok(None));
/// drop(s);
///
/// assert_eq!(r1.recv().await, Ok(1));
/// assert_eq!(r1.recv().await, Ok(2));
/// assert_eq!(r1.recv().await, Err(RecvError::Closed));
///
/// assert_eq!(r2.recv().await, Ok(2));
/// assert_eq!(r2.recv().await, Err(RecvError::Closed));
/// # });
/// ```
pub fn new_receiver(&self) -> Receiver<T> {
let mut inner = self.inner.lock().unwrap();
inner.receiver_count += 1;
Receiver {
inner: self.inner.clone(),
pos: inner.head_pos + inner.queue.len() as u64,
listener: None,
}
}
}
impl<T: Clone> Sender<T> {
/// Broadcasts a message on the channel.
///
/// If the channel is full, this method waits until there is space for a message unless:
///
/// 1. overflow mode (set through [`Sender::set_overflow`]) is enabled, in which case it removes
/// the oldest message from the channel to make room for the new message. The removed message
/// is returned to the caller.
/// 2. this behavior is disabled using [`Sender::set_await_active`], in which case, it returns
/// [`SendError`] immediately.
///
/// If the channel is closed, this method returns an error.
///
/// The future returned by this function is pinned to the heap. If the future being `Unpin` is
/// not important to you, or if you just `.await` this future, use the [`broadcast_direct`] method
/// instead.
///
/// # Examples
///
/// ```
/// # futures_lite::future::block_on(async {
/// use async_broadcast::{broadcast, SendError};
///
/// let (s, r) = broadcast(1);
///
/// assert_eq!(s.broadcast(1).await, Ok(None));
/// drop(r);
/// assert_eq!(s.broadcast(2).await, Err(SendError(2)));
/// # });
/// ```
pub fn broadcast(&self, msg: T) -> Pin<Box<Send<'_, T>>> {
Box::pin(self.broadcast_direct(msg))
}
/// Broadcasts a message on the channel without pinning the future to the heap.
///
/// The future returned by this method is not `Unpin` and must be pinned before use. This is
/// the desired behavior if you just `.await` on the future. For other uses cases, use the
/// [`broadcast`] method instead.
///
/// # Examples
///
/// ```
/// # futures_lite::future::block_on(async {
/// use async_broadcast::{broadcast, SendError};
///
/// let (s, r) = broadcast(1);
///
/// assert_eq!(s.broadcast_direct(1).await, Ok(None));
/// drop(r);
/// assert_eq!(s.broadcast_direct(2).await, Err(SendError(2)));
/// # });
/// ```
pub fn broadcast_direct(&self, msg: T) -> Send<'_, T> {
Send::_new(SendInner {
sender: self,
listener: None,
msg: Some(msg),
_pin: PhantomPinned,
})
}
/// Attempts to broadcast a message on the channel.
///
/// If the channel is full, this method returns an error unless overflow mode (set through
/// [`Sender::set_overflow`]) is enabled. If the overflow mode is enabled, it removes the
/// oldest message from the channel to make room for the new message. The removed message
/// is returned to the caller.
///
/// If the channel is closed, this method returns an error.
///
/// # Examples
///
/// ```
/// use async_broadcast::{broadcast, TrySendError};
///
/// let (s, r) = broadcast(1);
///
/// assert_eq!(s.try_broadcast(1), Ok(None));
/// assert_eq!(s.try_broadcast(2), Err(TrySendError::Full(2)));
///
/// drop(r);
/// assert_eq!(s.try_broadcast(3), Err(TrySendError::Closed(3)));
/// ```
pub fn try_broadcast(&self, msg: T) -> Result<Option<T>, TrySendError<T>> {
let mut ret = None;
let mut inner = self.inner.lock().unwrap();
if inner.is_closed {
return Err(TrySendError::Closed(msg));
} else if inner.receiver_count == 0 {
assert!(inner.inactive_receiver_count != 0);
return Err(TrySendError::Inactive(msg));
} else if inner.queue.len() == inner.capacity {
if inner.overflow {
// Make room by popping a message.
ret = inner.queue.pop_front().map(|(m, _)| m);
} else {
return Err(TrySendError::Full(msg));
}
}
let receiver_count = inner.receiver_count;
inner.queue.push_back((msg, receiver_count));
if ret.is_some() {
inner.head_pos += 1;
}
// Notify all awaiting receive operations.
inner.recv_ops.notify(usize::MAX);
Ok(ret)
}
/// Broadcasts a message on the channel using the blocking strategy.
///
/// If the channel is full, this method will block until there is room.
///
/// If the channel is closed, this method returns an error.
///
/// # Blocking
///
/// Rather than using asynchronous waiting, like the [`send`](Self::broadcast) method,
/// this method will block the current thread until the message is sent.
///
/// This method should not be used in an asynchronous context. It is intended
/// to be used such that a channel can be used in both asynchronous and synchronous contexts.
/// Calling this method in an asynchronous context may result in deadlocks.
///
/// # Examples
///
/// ```
/// use async_broadcast::{broadcast, SendError};
///
/// let (s, r) = broadcast(1);
///
/// assert_eq!(s.broadcast_blocking(1), Ok(None));
/// drop(r);
/// assert_eq!(s.broadcast_blocking(2), Err(SendError(2)));
/// ```
#[cfg(not(target_family = "wasm"))]
pub fn broadcast_blocking(&self, msg: T) -> Result<Option<T>, SendError<T>> {
self.broadcast_direct(msg).wait()
}
}
impl<T> Drop for Sender<T> {
fn drop(&mut self) {
let mut inner = self.inner.lock().unwrap();
inner.sender_count -= 1;
if inner.sender_count == 0 {
inner.close();
}
}
}
impl<T> Clone for Sender<T> {
fn clone(&self) -> Self {
self.inner.lock().unwrap().sender_count += 1;
Sender {
inner: self.inner.clone(),
}
}
}
/// The receiving side of a channel.
///
/// Receivers can be cloned and shared among threads. When all (active) receivers associated with a
/// channel are dropped, the channel becomes closed. You can deactivate a receiver using
/// [`Receiver::deactivate`] if you would like the channel to remain open without keeping active
/// receivers around.
#[derive(Debug)]
pub struct Receiver<T> {
inner: Arc<Mutex<Inner<T>>>,
pos: u64,
/// Listens for a send or close event to unblock this stream.
listener: Option<EventListener>,
}
impl<T> Receiver<T> {
/// Returns the channel capacity.
///
/// # Examples
///
/// ```
/// use async_broadcast::broadcast;
///
/// let (_s, r) = broadcast::<i32>(5);
/// assert_eq!(r.capacity(), 5);
/// ```
pub fn capacity(&self) -> usize {
self.inner.lock().unwrap().capacity
}
/// Set the channel capacity.
///
/// There are times when you need to change the channel's capacity after creating it. If the
/// `new_cap` is less than the number of messages in the channel, the oldest messages will be
/// dropped to shrink the channel.
///
/// # Examples
///
/// ```
/// use async_broadcast::{broadcast, TrySendError, TryRecvError};
///
/// let (s, mut r) = broadcast::<i32>(3);
/// assert_eq!(r.capacity(), 3);
/// s.try_broadcast(1).unwrap();
/// s.try_broadcast(2).unwrap();
/// s.try_broadcast(3).unwrap();
///
/// r.set_capacity(1);
/// assert_eq!(r.capacity(), 1);
/// assert_eq!(r.try_recv(), Err(TryRecvError::Overflowed(2)));
/// assert_eq!(r.try_recv().unwrap(), 3);
/// assert_eq!(r.try_recv(), Err(TryRecvError::Empty));
/// s.try_broadcast(1).unwrap();
/// assert_eq!(s.try_broadcast(2), Err(TrySendError::Full(2)));
///
/// r.set_capacity(2);
/// assert_eq!(r.capacity(), 2);
/// s.try_broadcast(2).unwrap();
/// assert_eq!(s.try_broadcast(2), Err(TrySendError::Full(2)));
/// ```
pub fn set_capacity(&mut self, new_cap: usize) {
self.inner.lock().unwrap().set_capacity(new_cap);
}
/// If overflow mode is enabled on this channel.
///
/// # Examples
///
/// ```
/// use async_broadcast::broadcast;
///
/// let (_s, r) = broadcast::<i32>(5);
/// assert!(!r.overflow());
/// ```
pub fn overflow(&self) -> bool {
self.inner.lock().unwrap().overflow
}
/// Set overflow mode on the channel.
///
/// When overflow mode is set, broadcasting to the channel will succeed even if the channel is
/// full. It achieves that by removing the oldest message from the channel.
///
/// # Examples
///
/// ```
/// use async_broadcast::{broadcast, TrySendError, TryRecvError};
///
/// let (s, mut r) = broadcast::<i32>(2);
/// s.try_broadcast(1).unwrap();
/// s.try_broadcast(2).unwrap();
/// assert_eq!(s.try_broadcast(3), Err(TrySendError::Full(3)));
/// r.set_overflow(true);
/// assert_eq!(s.try_broadcast(3).unwrap(), Some(1));
/// assert_eq!(s.try_broadcast(4).unwrap(), Some(2));
///
/// assert_eq!(r.try_recv(), Err(TryRecvError::Overflowed(2)));
/// assert_eq!(r.try_recv().unwrap(), 3);
/// assert_eq!(r.try_recv().unwrap(), 4);
/// assert_eq!(r.try_recv(), Err(TryRecvError::Empty));
/// ```
pub fn set_overflow(&mut self, overflow: bool) {
self.inner.lock().unwrap().overflow = overflow;
}
/// If sender will wait for active receivers.
///
/// If set to `false`, [`Send`] will resolve immediately with a [`SendError`]. Defaults to
/// `true`.
///
/// # Examples
///
/// ```
/// use async_broadcast::broadcast;
///
/// let (_, r) = broadcast::<i32>(5);
/// assert!(r.await_active());
/// ```
pub fn await_active(&self) -> bool {
self.inner.lock().unwrap().await_active
}
/// Specify if sender will wait for active receivers.
///
/// If set to `false`, [`Send`] will resolve immediately with a [`SendError`]. Defaults to
/// `true`.
///
/// # Examples
///
/// ```
/// # futures_lite::future::block_on(async {
/// use async_broadcast::broadcast;
///
/// let (s, mut r) = broadcast::<i32>(2);
/// s.broadcast(1).await.unwrap();
///
/// r.set_await_active(false);
/// let _ = r.deactivate();
/// assert!(s.broadcast(2).await.is_err());
/// # });
/// ```
pub fn set_await_active(&mut self, await_active: bool) {
self.inner.lock().unwrap().await_active = await_active;
}
/// Closes the channel.
///
/// Returns `true` if this call has closed the channel and it was not closed already.
///
/// The remaining messages can still be received.
///
/// # Examples
///
/// ```
/// # futures_lite::future::block_on(async {
/// use async_broadcast::{broadcast, RecvError};
///
/// let (s, mut r) = broadcast(1);
/// s.broadcast(1).await.unwrap();
/// assert!(s.close());
///
/// assert_eq!(r.recv().await.unwrap(), 1);
/// assert_eq!(r.recv().await, Err(RecvError::Closed));
/// # });
/// ```
pub fn close(&self) -> bool {
self.inner.lock().unwrap().close()
}
/// Returns `true` if the channel is closed.
///
/// # Examples
///
/// ```
/// # futures_lite::future::block_on(async {
/// use async_broadcast::{broadcast, RecvError};
///
/// let (s, r) = broadcast::<()>(1);
/// assert!(!s.is_closed());
///
/// drop(r);
/// assert!(s.is_closed());
/// # });
/// ```
pub fn is_closed(&self) -> bool {
self.inner.lock().unwrap().is_closed
}
/// Returns `true` if the channel is empty.
///
/// # Examples