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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 "qpid/sys/Monitor.h"
#include "qpid/sys/ExceptionHolder.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.
*
* Allows waiting threads to be interrupted by an exception.
*/
class Waitable : public Monitor {
public:
Waitable() : waiters(0) {}
~Waitable() { assert(waiters == 0); }
/** Use this inside a scoped lock around the
* call to 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 waiters in ScopedWaits.
* waitWaiters() does not raise an exception even if waiters
* were interrupted by one.
*@pre Must be called inside a ScopedLock but NOT a ScopedWait.
*/
void waitWaiters() {
while (waiters != 0)
Monitor::wait();
}
/** Returns the number of outstanding ScopedWaits.
* Must be called with the lock held.
*/
size_t hasWaiters() const {
return waiters;
}
/** Set an execption to interrupt waiters in ScopedWait.
* Must be called with the lock held.
*/
void setException(const ExceptionHolder& e) {
exception = e;
notifyAll();
}
/** True if the waitable has an exception */
bool hasException() const { return exception; }
/** Throws if the waitable has an exception */
void checkException() const { exception.raise(); }
/** Clear the exception if any */
void resetException() { exception.reset(); }
/** Throws an exception if one is set before or during the wait. */
void wait() {
ExCheck e(exception);
Monitor::wait();
}
/** Throws an exception if one is set before or during the wait. */
bool wait(const AbsTime& absoluteTime) {
ExCheck e(exception);
return Monitor::wait(absoluteTime);
}
private:
struct ExCheck {
const ExceptionHolder& exception;
ExCheck(const ExceptionHolder& e) : exception(e) { e.raise(); }
~ExCheck() { exception.raise(); }
};
size_t waiters;
ExceptionHolder exception;
friend struct ScopedWait;
};
}} // namespace qpid::sys
#endif /*!QPID_SYS_WAITABLE_H*/
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