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#ifndef QPID_SYS_STOPPABLE_H
#define QPID_SYS_STOPPABLE_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.
*
*/
namespace qpid {
namespace sys {
/**
* An activity that may be executed by multiple threads, and can be stopped.
* Stopping prevents new threads from entering and waits till exiting busy threads leave.
*/
class Stoppable {
public:
Stoppable() : busy(0), stopped(false) {}
~Stoppable() { stop(); }
/** Mark the scope of a busy thread like this:
* <pre>
* {
* Stoppable::Scope working(stoppable);
* if (working) { do stuff }
* }
* </pre>
*/
class Scope {
Stoppable& state;
bool entered;
public:
Scope(Stoppable& s) : state(s) { entered = s.enter(); }
~Scope() { if (entered) state.exit(); }
operator bool() const { return entered; }
};
friend class Scope;
/** Mark stopped, wait for all threads to leave their busy scope. */
void stop() {
sys::Monitor::ScopedLock l(lock);
stopped = true;
while (busy > 0) lock.wait();
}
/** Set the state to started.
*@pre state is stopped and no theads are busy.
*/
void start() {
sys::Monitor::ScopedLock l(lock);
assert(stopped && busy == 0); // FIXME aconway 2011-05-06: error handling.
stopped = false;
}
private:
uint busy;
bool stopped;
sys::Monitor lock;
bool enter() {
sys::Monitor::ScopedLock l(lock);
if (!stopped) ++busy;
return !stopped;
}
void exit() {
sys::Monitor::ScopedLock l(lock);
assert(busy > 0);
if (--busy == 0) lock.notifyAll();
}
};
}} // namespace qpid::sys
#endif /*!QPID_SYS_STOPPABLE_H*/
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