Struct Queue

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

Expand description

Queue is a lock-free concurrent first-in-first-out container.

Implementations§

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impl<T: 'static> Queue<T>

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pub fn push(&self, val: T) -> Shared<Entry<T>>

Pushes an instance of T.

Returns a Shared holding a strong reference to the newly pushed entry.

§Examples

use scc::Queue;

let queue: Queue<usize> = Queue::default();

assert_eq!(**queue.push(11), 11);

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pub fn push_if<F: FnMut(Option<&Entry<T>>) -> bool>( &self, val: T, cond: F, ) -> Result<Shared<Entry<T>>, T>

Pushes an instance of T if the newest entry satisfies the given condition.

§Errors

Returns an error along with the supplied instance if the condition is not met.

§Examples

use scc::Queue;

let queue: Queue<usize> = Queue::default();

queue.push(11);

assert!(queue.push_if(17, |e| e.map_or(false, |x| **x == 11)).is_ok());
assert!(queue.push_if(29, |e| e.map_or(false, |x| **x == 11)).is_err());

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pub fn peek<'g>(&self, guard: &'g Guard) -> Option<&'g Entry<T>>

Returns a guarded reference to the oldest entry.

Returns None if the Queue is empty. The returned reference can survive as long as the associated Guard is alive.

§Examples

use scc::ebr::Guard;
use scc::Queue;

let queue: Queue<usize> = Queue::default();

assert!(queue.peek(&Guard::new()).is_none());

queue.push(37);
queue.push(3);

assert_eq!(**queue.peek(&Guard::new()).unwrap(), 37);

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impl<T> Queue<T>

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pub unsafe fn push_unchecked(&self, val: T) -> Shared<Entry<T>>

Pushes an instance of T without checking the lifetime of T.

Returns a Shared holding a strong reference to the newly pushed entry.

§Safety

T::drop can be run after the Queue is dropped, therefore it is safe only if T::drop does not access short-lived data or std::mem::needs_drop is false for T,

§Examples

use scc::Queue;

let hello = String::from("hello");
let queue: Queue<&str> = Queue::default();

assert_eq!(unsafe { **queue.push_unchecked(hello.as_str()) }, "hello");

Source

pub unsafe fn push_if_unchecked<F: FnMut(Option<&Entry<T>>) -> bool>( &self, val: T, cond: F, ) -> Result<Shared<Entry<T>>, T>

Pushes an instance of T if the newest entry satisfies the given condition without checking the lifetime of T

§Errors

Returns an error along with the supplied instance if the condition is not met.

§Safety

T::drop can be run after the Queue is dropped, therefore it is safe only if T::drop does not access short-lived data or std::mem::needs_drop is false for T,

§Examples

use scc::Queue;

let hello = String::from("hello");
let queue: Queue<&str> = Queue::default();

assert!(unsafe { queue.push_if_unchecked(hello.as_str(), |e| e.is_none()).is_ok() });

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pub fn pop(&self) -> Option<Shared<Entry<T>>>

Pops the oldest entry.

Returns None if the Queue is empty.

§Examples

use scc::Queue;

let queue: Queue<usize> = Queue::default();

queue.push(37);
queue.push(3);
queue.push(1);

assert_eq!(queue.pop().map(|e| **e), Some(37));
assert_eq!(queue.pop().map(|e| **e), Some(3));
assert_eq!(queue.pop().map(|e| **e), Some(1));
assert!(queue.pop().is_none());

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pub fn pop_if<F: FnMut(&Entry<T>) -> bool>( &self, cond: F, ) -> Result<Option<Shared<Entry<T>>>, Shared<Entry<T>>>

Pops the oldest entry if the entry satisfies the given condition.

Returns None if the Queue is empty.

§Errors

Returns an error along with the oldest entry if the given condition is not met.

§Examples

use scc::Queue;

let queue: Queue<usize> = Queue::default();

queue.push(3);
queue.push(1);

assert!(queue.pop_if(|v| **v == 1).is_err());
assert_eq!(queue.pop().map(|e| **e), Some(3));
assert_eq!(queue.pop_if(|v| **v == 1).ok().and_then(|e| e).map(|e| **e), Some(1));

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pub fn peek_with<R, F: FnOnce(Option<&Entry<T>>) -> R>(&self, reader: F) -> R

Peeks the oldest entry.

§Examples

use scc::Queue;

let queue: Queue<usize> = Queue::default();

assert!(queue.peek_with(|v| v.is_none()));

queue.push(37);
queue.push(3);

assert_eq!(queue.peek_with(|v| **v.unwrap()), 37);

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pub fn len(&self) -> usize

Returns the number of entries in the Queue.

This method iterates over all the entries in the Queue to count them, therefore its time complexity is O(N).

§Examples

use scc::Queue;

let queue: Queue<usize> = Queue::default();
assert_eq!(queue.len(), 0);

queue.push(7);
queue.push(11);
assert_eq!(queue.len(), 2);

queue.pop();
queue.pop();
assert_eq!(queue.len(), 0);

Source

pub fn is_empty(&self) -> bool

Returns true if the Queue is empty.

§Examples

use scc::Queue;

let queue: Queue<usize> = Queue::default();
assert!(queue.is_empty());

queue.push(7);
assert!(!queue.is_empty());

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pub fn iter<'g>(&self, guard: &'g Guard) -> Iter<'g, T> ⓘ

Returns an Iter.

§Examples

use scc::ebr::Guard;
use scc::Queue;

let queue: Queue<usize> = Queue::default();
assert_eq!(queue.iter(&Guard::new()).count(), 0);

queue.push(7);
queue.push(11);
queue.push(17);

let guard = Guard::new();
let mut iter = queue.iter(&guard);
assert_eq!(*iter.next().unwrap(), 7);
assert_eq!(*iter.next().unwrap(), 11);
assert_eq!(*iter.next().unwrap(), 17);
assert!(iter.next().is_none());