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#ifndef QPID_SYS_POLLABLEQUEUE_H
#define QPID_SYS_POLLABLEQUEUE_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/PollableCondition.h"
#include "qpid/sys/Dispatcher.h"
#include "qpid/sys/Monitor.h"
#include <boost/function.hpp>
#include <boost/bind.hpp>
#include <algorithm>
#include <deque>
namespace qpid {
namespace sys {
class Poller;
/**
* A queue that can be polled by sys::Poller. Any thread can push to
* the queue, on wakeup the poller thread processes all items on the
* queue by passing them to a callback in a batch.
*/
template <class T>
class PollableQueue {
typedef std::deque<T> Queue;
public:
typedef typename Queue::iterator iterator;
/** Callback to process a range of items. */
typedef boost::function<void (const iterator&, const iterator&)> Callback;
/** @see forEach() */
template <class F> struct ForEach {
F handleOne;
ForEach(const F& f) : handleOne(f) {}
void operator()(const iterator& i, const iterator& j) const { std::for_each(i, j, handleOne); }
};
/** Create a range callback from a functor that processes a single item. */
template <class F> static ForEach<F> forEach(const F& f) { return ForEach<F>(f); }
/** When the queue is selected by the poller, values are passed to callback cb. */
explicit PollableQueue(const Callback& cb);
/** Push a value onto the queue. Thread safe */
void push(const T& t);
/** Start polling. */
void start(const boost::shared_ptr<sys::Poller>& poller);
/** Stop polling and wait for the current callback, if any, to complete. */
void stop();
/** Are we currently stopped?*/
bool isStopped() const;
private:
typedef sys::Monitor::ScopedLock ScopedLock;
typedef sys::Monitor::ScopedUnlock ScopedUnlock;
void dispatch(sys::DispatchHandle&);
mutable sys::Monitor lock;
Callback callback;
PollableCondition condition;
sys::DispatchHandle handle;
Queue queue;
Queue batch;
bool dispatching, stopped;
};
template <class T> PollableQueue<T>::PollableQueue(const Callback& cb) // FIXME aconway 2008-08-12:
: callback(cb),
handle(condition, boost::bind(&PollableQueue<T>::dispatch, this, _1), 0, 0),
dispatching(false), stopped(true)
{}
template <class T> void PollableQueue<T>::start(const boost::shared_ptr<sys::Poller>& poller) {
ScopedLock l(lock);
stopped = false;
handle.startWatch(poller);
}
template <class T> void PollableQueue<T>::push(const T& t) {
ScopedLock l(lock);
queue.push_back(t);
condition.set();
}
template <class T> void PollableQueue<T>::dispatch(sys::DispatchHandle& h) {
ScopedLock l(lock);
if (stopped) return;
dispatching = true;
condition.clear();
batch.clear();
batch.swap(queue); // Snapshot of current queue contents.
{
// Process outside the lock to allow concurrent push.
ScopedUnlock u(lock);
callback(batch.begin(), batch.end());
}
batch.clear();
dispatching = false;
if (stopped) lock.notifyAll();
else h.rewatch();
}
template <class T> void PollableQueue<T>::stop() {
ScopedLock l(lock);
handle.stopWatch();
stopped = true;
while (dispatching) lock.wait();
}
template <class T> bool PollableQueue<T>::isStopped() const {
ScopedLock l(lock);
return stopped;
}
}} // namespace qpid::sys
#endif /*!QPID_SYS_POLLABLEQUEUE_H*/
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