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// synchronization.h
/* Copyright 2010 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 <boost/thread/condition.hpp>
#include "mutex.h"
namespace mongo {
/*
* A class to establish a synchronization point between two threads. One thread is the waiter and one is
* the notifier. After the notification event, both proceed normally.
*
* This class is thread-safe.
*/
class Notification : boost::noncopyable {
public:
Notification();
/*
* Blocks until the method 'notifyOne()' is called.
*/
void waitToBeNotified();
/*
* Notifies the waiter of '*this' that it can proceed. Can only be called once.
*/
void notifyOne();
private:
mongo::mutex _mutex; // protects state below
unsigned long long lookFor;
unsigned long long cur;
boost::condition _condition; // cond over _notified being true
};
/** establishes a synchronization point between threads. N threads are waits and one is notifier.
threadsafe.
*/
class NotifyAll : boost::noncopyable {
public:
NotifyAll();
typedef unsigned long long When;
When now();
/** awaits the next notifyAll() call by another thread. notifications that precede this
call are ignored -- we are looking for a fresh event.
*/
void waitFor(When);
/** a bit faster than waitFor( now() ) */
void awaitBeyondNow();
/** may be called multiple times. notifies all waiters */
void notifyAll(When);
/** indicates how many threads are waiting for a notify. */
unsigned nWaiting() const { return _nWaiting; }
private:
mongo::mutex _mutex;
boost::condition _condition;
When _lastDone;
When _lastReturned;
unsigned _nWaiting;
};
} // namespace mongo
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