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// @file queue.h
/* Copyright 2009 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects
* for all of the code used other than as permitted herein. If you modify
* file(s) with this exception, you may extend this exception to your
* version of the file(s), but you are not obligated to do so. If you do not
* wish to do so, delete this exception statement from your version. If you
* delete this exception statement from all source files in the program,
* then also delete it in the license file.
*/
#pragma once
#include <limits>
#include <queue>
#include "mongo/stdx/chrono.h"
#include "mongo/stdx/condition_variable.h"
#include "mongo/base/disallow_copying.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.
*
* Note that use of this class is deprecated. This class only works with a single consumer and
* a single producer.
*/
template <typename T>
class BlockingQueue {
MONGO_DISALLOW_COPYING(BlockingQueue);
typedef size_t (*getSizeFunc)(const T& t);
public:
BlockingQueue()
: _maxSize(std::numeric_limits<std::size_t>::max()),
_currentSize(0),
_getSize(&_getSizeDefault) {}
BlockingQueue(size_t size) : _maxSize(size), _currentSize(0), _getSize(&_getSizeDefault) {}
BlockingQueue(size_t size, getSizeFunc f) : _maxSize(size), _currentSize(0), _getSize(f) {}
void push(T const& t) {
stdx::unique_lock<stdx::mutex> l(_lock);
size_t tSize = _getSize(t);
while (_currentSize + tSize > _maxSize) {
_cvNoLongerFull.wait(l);
}
_queue.push(t);
_currentSize += tSize;
_cvNoLongerEmpty.notify_one();
}
bool empty() const {
stdx::lock_guard<stdx::mutex> l(_lock);
return _queue.empty();
}
/**
* The size as measured by the size function. Default to counting each item
*/
size_t size() const {
stdx::lock_guard<stdx::mutex> 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() )
*/
size_t count() const {
stdx::lock_guard<stdx::mutex> l(_lock);
return _queue.size();
}
void clear() {
stdx::lock_guard<stdx::mutex> l(_lock);
_queue = std::queue<T>();
_currentSize = 0;
_cvNoLongerFull.notify_one();
}
bool tryPop(T& t) {
stdx::lock_guard<stdx::mutex> l(_lock);
if (_queue.empty())
return false;
t = _queue.front();
_queue.pop();
_currentSize -= _getSize(t);
_cvNoLongerFull.notify_one();
return true;
}
T blockingPop() {
stdx::unique_lock<stdx::mutex> l(_lock);
while (_queue.empty())
_cvNoLongerEmpty.wait(l);
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) {
using namespace stdx::chrono;
const auto deadline = system_clock::now() + seconds(maxSecondsToWait);
stdx::unique_lock<stdx::mutex> l(_lock);
while (_queue.empty()) {
if (stdx::cv_status::timeout == _cvNoLongerEmpty.wait_until(l, deadline))
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) {
using namespace stdx::chrono;
const auto deadline = system_clock::now() + seconds(maxSecondsToWait);
stdx::unique_lock<stdx::mutex> l(_lock);
while (_queue.empty()) {
if (stdx::cv_status::timeout == _cvNoLongerEmpty.wait_until(l, deadline))
return false;
}
t = _queue.front();
return true;
}
// Obviously, this should only be used when you have
// only one consumer
bool peek(T& t) {
stdx::unique_lock<stdx::mutex> l(_lock);
if (_queue.empty()) {
return false;
}
t = _queue.front();
return true;
}
private:
mutable stdx::mutex _lock;
std::queue<T> _queue;
const size_t _maxSize;
size_t _currentSize;
getSizeFunc _getSize;
stdx::condition_variable _cvNoLongerFull;
stdx::condition_variable _cvNoLongerEmpty;
};
}
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