Struct scc::Queue

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

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

Implementations

impl<T: 'static> Queue<T>

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

Pushes an instance of T.

Returns an Arc 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);

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

pub fn peek_with<'b, R, F: FnOnce(Option<&'b Entry<T>>) -> R>( &self, reader: F, barrier: &'b Barrier ) -> R

Peeks the oldest entry with the supplied Barrier.

Examples

use scc::ebr::Barrier;
use scc::Queue;

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

assert!(queue.peek_with(|v| v.is_none(), &Barrier::new()));

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

assert_eq!(queue.peek_with(|v| **v.unwrap(), &Barrier::new()), 37);

impl<T> Queue<T>

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

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

Returns an Arc 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");

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

pub fn pop(&self) -> Option<Arc<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());

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

pub fn peek<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(|v| v.is_none()));

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

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

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());

Trait Implementations

impl<T: Clone> Clone for Queue<T>

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug> Debug for Queue<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T> Default for Queue<T>

fn default() -> Self

Returns the “default value” for a type.