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#ifndef QPID_SYS_WAITABLE_H
#define QPID_SYS_WAITABLE_H
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.
*
*/
#include "Monitor.h"
#include <assert.h>
namespace qpid {
namespace sys {
/**
* A monitor that keeps track of waiting threads. Threads declare a
* ScopedWait around wait() inside a ScopedLock to be considered
* waiters.
*/
class Waitable : public Monitor {
public:
Waitable() : waiters(0) {}
/** Use this inside a scoped lock around the
* call to Monitor::wait to be counted as a waiter
*/
struct ScopedWait {
Waitable& w;
ScopedWait(Waitable& w_) : w(w_) { ++w.waiters; }
~ScopedWait() { if (--w.waiters==0) w.notifyAll(); }
};
/** Block till there are no more ScopedWaits.
*@pre Must be called inside a ScopedLock but NOT a ScopedWait.
*/
void waitWaiters() {
while (waiters != 0)
wait();
}
/** Returns the number of outstanding ScopedWaits.
* Must be called with the lock held.
*/
size_t hasWaiters() { return waiters; }
private:
friend struct ScopedWait;
size_t waiters;
};
}} // namespace qpid::sys
#endif /*!QPID_SYS_WAITABLE_H*/
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