Struct tokio::sync::mpsc::OwnedPermit

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

Expand description

Owned permit to send one value into the channel.

This is identical to the Permit type, except that it moves the sender rather than borrowing it.

OwnedPermit values are returned by Sender::reserve_owned() and Sender::try_reserve_owned() and are used to guarantee channel capacity before generating a message to send.

Implementations

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impl<T> OwnedPermit<T>

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pub fn send(self, value: T) -> Sender<T>

Sends a value using the reserved capacity.

Capacity for the message has already been reserved. The message is sent to the receiver and the permit is consumed. The operation will succeed even if the receiver half has been closed. See Receiver::close for more details on performing a clean shutdown.

Unlike Permit::send, this method returns the Sender from which the OwnedPermit was reserved.

Examples

use tokio::sync::mpsc;

#[tokio::main]
async fn main() {
    let (tx, mut rx) = mpsc::channel(1);

    // Reserve capacity
    let permit = tx.reserve_owned().await.unwrap();

    // Send a message on the permit, returning the sender.
    let tx = permit.send(456);

    // The value sent on the permit is received
    assert_eq!(rx.recv().await.unwrap(), 456);

    // We may now reuse `tx` to send another message.
    tx.send(789).await.unwrap();
}

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pub fn release(self) -> Sender<T>

Releases the reserved capacity without sending a message, returning the Sender.

Examples

use tokio::sync::mpsc;

#[tokio::main]
async fn main() {
    let (tx, rx) = mpsc::channel(1);

    // Clone the sender and reserve capacity
    let permit = tx.clone().reserve_owned().await.unwrap();

    // Trying to send on the original `tx` will fail, since the `permit`
    // has reserved all the available capacity.
    assert!(tx.try_send(123).is_err());

    // Release the permit without sending a message, returning the clone
    // of the sender.
    let tx2 = permit.release();

    // We may now reuse `tx` to send another message.
    tx.send(789).await.unwrap();
}