# tokio::sync::Barrier - Rust
API documentation for the Rust `Barrier` struct in crate `tokio`.
Keywords: rust, rustlang, rust-lang, Barrier

# Struct tokio::sync::Barrier [−] [src]

    pub struct Barrier { /* fields omitted */ }

A barrier enables multiple threads to synchronize the beginning of some computation.

    use tokio::sync::Barrier;
    use std::sync::Arc;

    let mut handles = Vec::with_capacity(10);
    let barrier = Arc::new(Barrier::new(10));
    for _ in 0..10 {
        let c = barrier.clone();
        // The same messages will be printed together.
        // You will NOT see any interleaving.
        handles.push(tokio::spawn(async move {
            println!("before wait");
            let wait_result = c.wait().await;
            println!("after wait");
            wait_result
        }));
    }

    // Will not resolve until all "after wait" messages have been printed
    let mut num_leaders = 0;
    for handle in handles {
        let wait_result = handle.await.unwrap();
        if wait_result.is_leader() {
            num_leaders += 1;
        }
    }

    // Exactly one barrier will resolve as the "leader"
    assert_eq!(num_leaders, 1);

## Implementations

### `impl Barrier` [src]

#### `pub fn new(n: usize) -> Barrier` [src]

Creates a new barrier that can block a given number of threads.

A barrier will block `n`-1 threads which call `Barrier::wait` and then wake up all threads at once when the `n`th thread calls `wait`.

#### `pub async fn wait(&self) -> BarrierWaitResult` [src]

Does not resolve until all tasks have rendezvoused here.

Barriers are re-usable after all threads have rendezvoused once, and can be used continuously.

A single (arbitrary) future will receive a `BarrierWaitResult` that returns `true` from `BarrierWaitResult::is_leader` when returning from this function, and all other threads will receive a result that will return `false` from `is_leader`.

## Trait Implementations

### `impl Debug for Barrier` [src]

#### `fn fmt(&self, f: &mut Formatter<'_>) -> Result` [src]

Formats the value using the given formatter. Read more

## Auto Trait Implementations

### `impl !RefUnwindSafe for Barrier` [src]

### `impl Send for Barrier` [src]

### `impl Sync for Barrier` [src]

### `impl Unpin for Barrier` [src]

### `impl !UnwindSafe for Barrier` [src]

## Blanket Implementations

### `impl<T> Any for T where
T: 'static + ?Sized,` [src]

#### `pub fn type_id(&self) -> TypeId` [src]

Gets the `TypeId` of `self`. Read more

### `impl<T> Borrow<T> for T where
T: ?Sized,` [src]

#### `pub fn borrow(&self) -> &Tⓘ

### Notable traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;`
` [src]

Immutably borrows from an owned value. Read more

### `impl<T> BorrowMut<T> for T where
T: ?Sized,` [src]

#### `pub fn borrow_mut(&mut self) -> &mut Tⓘ

### Notable traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;`
` [src]

Mutably borrows from an owned value. Read more

### `impl<T> From<T> for T` [src]

#### `pub fn from(t: T) -> T` [src]

Performs the conversion.

### `impl<T, U> Into<U> for T where
U: From<T>,` [src]

#### `pub fn into(self) -> U` [src]

Performs the conversion.

### `impl<T, U> TryFrom<U> for T where
U: Into<T>,` [src]

#### `type Error = Infallible`

The type returned in the event of a conversion error.

#### `pub fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>` [src]

Performs the conversion.

### `impl<T, U> TryInto<U> for T where
U: TryFrom<T>,` [src]

#### `type Error = <U as TryFrom<T>>::Error`

The type returned in the event of a conversion error.

#### `pub fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>` [src]

Performs the conversion.