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// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! Maintains a shared list of sleeping schedulers. Schedulers
//! use this to wake each other up.
use container::Container;
use vec::OwnedVector;
use option::{Option, Some, None};
use cell::Cell;
use unstable::sync::{UnsafeArc, LittleLock};
use rt::sched::SchedHandle;
use clone::Clone;
pub struct SleeperList {
priv state: UnsafeArc<State>
}
struct State {
count: uint,
stack: ~[SchedHandle],
lock: LittleLock
}
impl SleeperList {
pub fn new() -> SleeperList {
SleeperList {
state: UnsafeArc::new(State {
count: 0,
stack: ~[],
lock: LittleLock::new()
})
}
}
pub fn push(&mut self, handle: SchedHandle) {
let handle = Cell::new(handle);
unsafe {
let state = self.state.get();
do (*state).lock.lock {
(*state).count += 1;
(*state).stack.push(handle.take());
}
}
}
pub fn pop(&mut self) -> Option<SchedHandle> {
unsafe {
let state = self.state.get();
do (*state).lock.lock {
if !(*state).stack.is_empty() {
(*state).count -= 1;
Some((*state).stack.pop())
} else {
None
}
}
}
}
/// A pop that may sometimes miss enqueued elements, but is much faster
/// to give up without doing any synchronization
pub fn casual_pop(&mut self) -> Option<SchedHandle> {
unsafe {
let state = self.state.get();
// NB: Unsynchronized check
if (*state).count == 0 { return None; }
do (*state).lock.lock {
if !(*state).stack.is_empty() {
// NB: count is also protected by the lock
(*state).count -= 1;
Some((*state).stack.pop())
} else {
None
}
}
}
}
}
impl Clone for SleeperList {
fn clone(&self) -> SleeperList {
SleeperList {
state: self.state.clone()
}
}
}
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