94 lines
2.5 KiB
Rust
94 lines
2.5 KiB
Rust
// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! A concurrent queue that supports multiple producers and a
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//! single consumer.
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use container::Container;
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use kinds::Send;
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use vec::OwnedVector;
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use cell::Cell;
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use option::*;
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use unstable::sync::{UnsafeArc, LittleLock};
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use clone::Clone;
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pub struct MessageQueue<T> {
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priv state: UnsafeArc<State<T>>
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}
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struct State<T> {
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count: uint,
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queue: ~[T],
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lock: LittleLock
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}
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impl<T: Send> MessageQueue<T> {
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pub fn new() -> MessageQueue<T> {
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MessageQueue {
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state: UnsafeArc::new(State {
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count: 0,
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queue: ~[],
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lock: LittleLock::new()
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})
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}
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}
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pub fn push(&mut self, value: T) {
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unsafe {
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let value = Cell::new(value);
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let state = self.state.get();
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do (*state).lock.lock {
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(*state).count += 1;
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(*state).queue.push(value.take());
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}
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}
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}
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pub fn pop(&mut self) -> Option<T> {
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unsafe {
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let state = self.state.get();
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do (*state).lock.lock {
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if !(*state).queue.is_empty() {
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(*state).count += 1;
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Some((*state).queue.shift())
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} else {
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None
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}
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}
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}
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}
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/// A pop that may sometimes miss enqueued elements, but is much faster
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/// to give up without doing any synchronization
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pub fn casual_pop(&mut self) -> Option<T> {
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unsafe {
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let state = self.state.get();
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// NB: Unsynchronized check
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if (*state).count == 0 { return None; }
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do (*state).lock.lock {
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if !(*state).queue.is_empty() {
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(*state).count += 1;
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Some((*state).queue.shift())
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} else {
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None
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}
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}
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}
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}
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}
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impl<T: Send> Clone for MessageQueue<T> {
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fn clone(&self) -> MessageQueue<T> {
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MessageQueue {
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state: self.state.clone()
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}
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}
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}
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