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// @file queue.h
/* Copyright 2009 10gen Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#pragma once
#include "mongo/pch.h"
#include <limits>
#include <queue>
#include <boost/thread/condition.hpp>
#include "mongo/util/timer.h"
namespace mongo {
template <typename T>
size_t _getSizeDefault(const T& t) {
return 1;
}
/**
* Simple blocking queue with optional max size (by count or custom sizing function).
* A custom sizing function can optionally be given. By default the getSize function
* returns 1 for each item, resulting in size equaling the number of items queued.
*/
template<typename T>
class BlockingQueue : boost::noncopyable {
typedef size_t (*getSizeFunc)(const T& t);
public:
BlockingQueue() :
_lock("BlockingQueue"),
_maxSize(std::numeric_limits<std::size_t>::max()),
_currentSize(0),
_getSize(&_getSizeDefault) {}
BlockingQueue(size_t size) :
_lock("BlockingQueue(bounded)"),
_maxSize(size),
_currentSize(0),
_getSize(&_getSizeDefault) {}
BlockingQueue(size_t size, getSizeFunc f) :
_lock("BlockingQueue(custom size)"),
_maxSize(size),
_currentSize(0),
_getSize(f) {}
void push(T const& t) {
scoped_lock l( _lock );
size_t tSize = _getSize(t);
while (_currentSize + tSize >= _maxSize) {
_cvNoLongerFull.wait( l.boost() );
}
_queue.push( t );
_currentSize += tSize;
_cvNoLongerEmpty.notify_one();
}
bool empty() const {
scoped_lock l( _lock );
return _queue.empty();
}
/**
* The size as measured by the size function. Default to counting each item
*/
size_t size() const {
scoped_lock l( _lock );
return _currentSize;
}
/**
* The max size for this queue
*/
size_t maxSize() const {
return _maxSize;
}
/**
* The number/count of items in the queue ( _queue.size() )
*/
int count() const {
scoped_lock l( _lock );
return _queue.size();
}
void clear() {
scoped_lock l(_lock);
_queue = std::queue<T>();
_currentSize = 0;
}
bool tryPop( T & t ) {
scoped_lock l( _lock );
if ( _queue.empty() )
return false;
t = _queue.front();
_queue.pop();
_currentSize -= _getSize(t);
_cvNoLongerFull.notify_one();
return true;
}
T blockingPop() {
scoped_lock l( _lock );
while( _queue.empty() )
_cvNoLongerEmpty.wait( l.boost() );
T t = _queue.front();
_queue.pop();
_currentSize -= _getSize(t);
_cvNoLongerFull.notify_one();
return t;
}
/**
* blocks waiting for an object until maxSecondsToWait passes
* if got one, return true and set in t
* otherwise return false and t won't be changed
*/
bool blockingPop( T& t , int maxSecondsToWait ) {
Timer timer;
boost::xtime xt;
boost::xtime_get(&xt, MONGO_BOOST_TIME_UTC);
xt.sec += maxSecondsToWait;
scoped_lock l( _lock );
while( _queue.empty() ) {
if ( ! _cvNoLongerEmpty.timed_wait( l.boost() , xt ) )
return false;
}
t = _queue.front();
_queue.pop();
_currentSize -= _getSize(t);
_cvNoLongerFull.notify_one();
return true;
}
// Obviously, this should only be used when you have
// only one consumer
bool blockingPeek(T& t, int maxSecondsToWait) {
Timer timer;
boost::xtime xt;
boost::xtime_get(&xt, MONGO_BOOST_TIME_UTC);
xt.sec += maxSecondsToWait;
scoped_lock l( _lock );
while( _queue.empty() ) {
if ( ! _cvNoLongerEmpty.timed_wait( l.boost() , xt ) )
return false;
}
t = _queue.front();
return true;
}
// Obviously, this should only be used when you have
// only one consumer
bool peek(T& t) {
scoped_lock l( _lock );
if (_queue.empty()) {
return false;
}
t = _queue.front();
return true;
}
private:
mutable mongo::mutex _lock;
std::queue<T> _queue;
const size_t _maxSize;
size_t _currentSize;
getSizeFunc _getSize;
boost::condition _cvNoLongerFull;
boost::condition _cvNoLongerEmpty;
};
}
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