// @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 .
*
* 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
#include
#include
#include "mongo/base/disallow_copying.h"
#include "mongo/stdx/chrono.h"
#include "mongo/stdx/condition_variable.h"
#include "mongo/stdx/functional.h"
#include "mongo/stdx/mutex.h"
namespace mongo {
/**
* 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
class BlockingQueue {
MONGO_DISALLOW_COPYING(BlockingQueue);
public:
using GetSizeFn = stdx::function;
BlockingQueue() : BlockingQueue(std::numeric_limits::max()) {}
BlockingQueue(size_t size) : BlockingQueue(size, [](const T&) { return 1; }) {}
BlockingQueue(size_t size, GetSizeFn f) : _maxSize(size), _getSize(f) {}
void pushEvenIfFull(T const& t) {
stdx::unique_lock lk(_lock);
pushImpl_inlock(t, _getSize(t));
}
void push(T const& t) {
stdx::unique_lock lk(_lock);
_clearing = false;
size_t tSize = _getSize(t);
_waitForSpace_inlock(tSize, lk);
pushImpl_inlock(t, tSize);
}
/**
* Caller must ensure the BlockingQueue hasSpace before pushing since this function won't block.
*
* NOTE: Should only be used in a single producer case.
*/
template
void pushAllNonBlocking(const Container& objs) {
pushAllNonBlocking(std::begin(objs), std::end(objs));
}
template
void pushAllNonBlocking(Iterator begin, Iterator end) {
if (begin == end) {
return;
}
stdx::unique_lock lk(_lock);
const auto startedEmpty = _queue.empty();
_clearing = false;
auto pushOne = [this](const T& obj) {
size_t tSize = _getSize(obj);
_queue.push(obj);
_currentSize += tSize;
};
std::for_each(begin, end, pushOne);
if (startedEmpty) {
_cvNoLongerEmpty.notify_one();
}
}
/**
* Returns when enough space is available.
*
* NOTE: Should only be used in a single producer case.
*/
void waitForSpace(size_t size) {
stdx::unique_lock lk(_lock);
_waitForSpace_inlock(size, lk);
}
bool empty() const {
stdx::lock_guard lk(_lock);
return _queue.empty();
}
/**
* The size as measured by the size function. Default to counting each item
*/
size_t size() const {
stdx::lock_guard lk(_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 lk(_lock);
return _queue.size();
}
void clear() {
stdx::lock_guard lk(_lock);
_clearing = true;
_queue = std::queue();
_currentSize = 0;
_cvNoLongerFull.notify_one();
_cvNoLongerEmpty.notify_one();
}
bool tryPop(T& t) {
stdx::lock_guard lk(_lock);
if (_queue.empty())
return false;
t = _queue.front();
_queue.pop();
_currentSize -= _getSize(t);
_cvNoLongerFull.notify_one();
return true;
}
T blockingPop() {
stdx::unique_lock lk(_lock);
_clearing = false;
while (_queue.empty() && !_clearing)
_cvNoLongerEmpty.wait(lk);
if (_clearing) {
return T{};
}
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 lk(_lock);
_clearing = false;
while (_queue.empty() && !_clearing) {
if (stdx::cv_status::timeout == _cvNoLongerEmpty.wait_until(lk, deadline))
return false;
}
if (_clearing) {
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 lk(_lock);
_clearing = false;
while (_queue.empty() && !_clearing) {
if (stdx::cv_status::timeout == _cvNoLongerEmpty.wait_until(lk, deadline))
return false;
}
if (_clearing) {
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 lk(_lock);
if (_queue.empty()) {
return false;
}
t = _queue.front();
return true;
}
/**
* Returns the item most recently added to the queue or nothing if the queue is empty.
*/
boost::optional lastObjectPushed() const {
stdx::unique_lock lk(_lock);
if (_queue.empty()) {
return {};
}
return {_queue.back()};
}
private:
/**
* Returns when enough space is available.
*/
void _waitForSpace_inlock(size_t size, stdx::unique_lock& lk) {
while (_currentSize + size > _maxSize) {
_cvNoLongerFull.wait(lk);
}
}
void pushImpl_inlock(const T& obj, size_t objSize) {
_clearing = false;
_queue.push(obj);
_currentSize += objSize;
if (_queue.size() == 1) // We were empty.
_cvNoLongerEmpty.notify_one();
}
mutable stdx::mutex _lock;
std::queue _queue;
const size_t _maxSize;
size_t _currentSize = 0;
GetSizeFn _getSize;
bool _clearing = false;
stdx::condition_variable _cvNoLongerFull;
stdx::condition_variable _cvNoLongerEmpty;
};
}