std::sync::mpsc

Struct SyncSender

1.0.0 · source

pub struct SyncSender<T> { /* private fields */ }

Expand description

The sending-half of Rust’s synchronous sync_channel type.

Messages can be sent through this channel with send or try_send.

send will block if there is no space in the internal buffer.

§Examples

use std::sync::mpsc::sync_channel;
use std::thread;

// Create a sync_channel with buffer size 2
let (sync_sender, receiver) = sync_channel(2);
let sync_sender2 = sync_sender.clone();

// First thread owns sync_sender
thread::spawn(move || {
    sync_sender.send(1).unwrap();
    sync_sender.send(2).unwrap();
});

// Second thread owns sync_sender2
thread::spawn(move || {
    sync_sender2.send(3).unwrap();
    // thread will now block since the buffer is full
    println!("Thread unblocked!");
});

let mut msg;

msg = receiver.recv().unwrap();
println!("message {msg} received");

// "Thread unblocked!" will be printed now

msg = receiver.recv().unwrap();
println!("message {msg} received");

msg = receiver.recv().unwrap();

println!("message {msg} received");

Implementations§

source §

impl<T> SyncSender<T>

1.0.0 · source

pub fn send(&self, t: T) -> Result<(), SendError<T>>

Sends a value on this synchronous channel.

This function will block until space in the internal buffer becomes available or a receiver is available to hand off the message to.

Note that a successful send does not guarantee that the receiver will ever see the data if there is a buffer on this channel. Items may be enqueued in the internal buffer for the receiver to receive at a later time. If the buffer size is 0, however, the channel becomes a rendezvous channel and it guarantees that the receiver has indeed received the data if this function returns success.

This function will never panic, but it may return Err if the Receiver has disconnected and is no longer able to receive information.

§Examples

use std::sync::mpsc::sync_channel;
use std::thread;

// Create a rendezvous sync_channel with buffer size 0
let (sync_sender, receiver) = sync_channel(0);

thread::spawn(move || {
   println!("sending message...");
   sync_sender.send(1).unwrap();
   // Thread is now blocked until the message is received

   println!("...message received!");
});

let msg = receiver.recv().unwrap();
assert_eq!(1, msg);

1.0.0 · source

pub fn try_send(&self, t: T) -> Result<(), TrySendError<T>>

Attempts to send a value on this channel without blocking.

This method differs from send by returning immediately if the channel’s buffer is full or no receiver is waiting to acquire some data. Compared with send, this function has two failure cases instead of one (one for disconnection, one for a full buffer).

See send for notes about guarantees of whether the receiver has received the data or not if this function is successful.

§Examples

use std::sync::mpsc::sync_channel;
use std::thread;

// Create a sync_channel with buffer size 1
let (sync_sender, receiver) = sync_channel(1);
let sync_sender2 = sync_sender.clone();

// First thread owns sync_sender
thread::spawn(move || {
    sync_sender.send(1).unwrap();
    sync_sender.send(2).unwrap();
    // Thread blocked
});

// Second thread owns sync_sender2
thread::spawn(move || {
    // This will return an error and send
    // no message if the buffer is full
    let _ = sync_sender2.try_send(3);
});

let mut msg;
msg = receiver.recv().unwrap();
println!("message {msg} received");

msg = receiver.recv().unwrap();
println!("message {msg} received");

// Third message may have never been sent
match receiver.try_recv() {
    Ok(msg) => println!("message {msg} received"),
    Err(_) => println!("the third message was never sent"),
}