/**************************************************************
 * 
 * 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.
 * 
 *************************************************************/



#ifndef _SALHELPER_MONITOR_HXX_
#define _SALHELPER_MONITOR_HXX_

#include <sal/types.h>
#include <osl/conditn.hxx>
#include <osl/diagnose.h>
#include <osl/interlck.h>
#include <rtl/ref.hxx>
#include <salhelper/refobj.hxx>
#include <salhelper/future.hxx>
#include <salhelper/futurequeue.hxx>

namespace salhelper
{

//----------------------------------------------------------------------------

#ifndef SALHELPER_COPYCTOR_API
#define SALHELPER_COPYCTOR_API(C) C (const C&); C& operator= (const C&)
#endif

//----------------------------------------------------------------------------

class MonitorCondition : protected osl::Condition
{
	/** Representation.
	 */
	oslInterlockedCount m_nReferenceCount;

	/** Not implemented.
	 */
	SALHELPER_COPYCTOR_API(MonitorCondition);

public:
	/** Construction.
	 */
	inline MonitorCondition() SAL_THROW(()) : m_nReferenceCount (0)
	{
		Condition::set();
	}

	/** Destruction.
	 */
	inline ~MonitorCondition() SAL_THROW(())
	{
		OSL_ASSERT(m_nReferenceCount == 0);
	}

	/** Acquire or enter the monitor.
	 */
	inline void acquire() SAL_THROW(())
	{
		if (osl_incrementInterlockedCount (&m_nReferenceCount) == 1)
		{
			Condition::reset();
		}
	}

	/** Release or leave the monitor.
	 */
	inline void release() SAL_THROW(())
	{
		if (osl_decrementInterlockedCount (&m_nReferenceCount) == 0)
		{
			Condition::set();
		}
	}

	/** Wait until all references are released.
	 */
	inline void wait() SAL_THROW(())
	{
		Condition::wait();
	}
};
	
//----------------------------------------------------------------------------

class QueuedReaderWriterMonitor : public salhelper::ReferenceObject
{
	/** Representation.
	 */
	typedef salhelper::Future<sal_Int32> future_type;

	salhelper::FutureQueue<sal_Int32> m_aQueue;
	salhelper::MonitorCondition       m_aMonitor;

	/** Not implemented.
	 */
	SALHELPER_COPYCTOR_API(QueuedReaderWriterMonitor);

public:
	/** Construction.
	 */
	inline QueuedReaderWriterMonitor()
	{
		// Insert the token.
		m_aQueue.put(0);
	}

	/** Acquire read access.
	 */
	inline void acquireReader()
	{
		// Obtain the token.
		rtl::Reference<future_type> xFuture (m_aQueue.get());
		xFuture->get();

		// Enter the monitor.
		m_aMonitor.acquire();

		// Push back the token.
		m_aQueue.put(0);
	}

	/** Release read access.
	 */
	inline void releaseReader()
	{
		// Leave the monitor.
		m_aMonitor.release();
	}

	/** Acquire write access.
	 */
	inline void acquireWriter()
	{
		// Obtain the token.
		rtl::Reference<future_type> xFuture (m_aQueue.get());
		xFuture->get();

		// Wait until all readers have left.
		m_aMonitor.wait();
	}

	/** Release write access.
	 */
	inline void releaseWriter()
	{
		// Push back the token.
		m_aQueue.put(0);
	}

protected:
	/** Destruction.
	 */
	virtual ~QueuedReaderWriterMonitor()
	{}
};

//----------------------------------------------------------------------------

template<class monitor_type>
class ReaderGuard
{
	/** Representation.
	 */
	monitor_type *m_pMonitor;

	/** Not implemented.
	 */
	SALHELPER_COPYCTOR_API(ReaderGuard<monitor_type>);

public:
	/** Construction. Acquire monitor read access.
	 */
	inline ReaderGuard (monitor_type & rMonitor) : m_pMonitor (&rMonitor)
	{
		m_pMonitor->acquireReader();
	}

	/** Construction. Acquire monitor read access.
	 */
	inline ReaderGuard (monitor_type * pMonitor) : m_pMonitor (pMonitor)
	{
		OSL_PRECOND(m_pMonitor, "ReaderGuard::ReaderGuard(): No Monitor");
		m_pMonitor->acquireReader();
	}

	/** Destruction. Release monitor read access.
	 */
	inline ~ReaderGuard()
	{
		if (m_pMonitor)
			m_pMonitor->releaseReader();
	}

	/** Release monitor read access.
	 */
	inline void clear()
	{
		if (m_pMonitor)
		{
			m_pMonitor->releaseReader();
			m_pMonitor = 0;
		}
	}
};

//----------------------------------------------------------------------------

typedef ReaderGuard<QueuedReaderWriterMonitor> QueuedReaderGuard;

//----------------------------------------------------------------------------

template<class monitor_type>
class WriterGuard
{
	/** Representation.
	 */
	monitor_type *m_pMonitor;

	/** Not implemented.
	 */
	SALHELPER_COPYCTOR_API(WriterGuard<monitor_type>);

public:
	/** Construction. Acquire monitor write access.
	 */
	inline WriterGuard (monitor_type & rMonitor) : m_pMonitor (&rMonitor)
	{
		m_pMonitor->acquireWriter();
	}

	/** Construction. Acquire monitor write access.
	 */
	inline WriterGuard (monitor_type * pMonitor) : m_pMonitor (pMonitor)
	{
		OSL_PRECOND(m_pMonitor, "WriterGuard::WriterGuard(): No Monitor");
		m_pMonitor->acquireWriter();
	}

	/** Destruction. Release monitor write access.
	 */
	inline ~WriterGuard()
	{
		if (m_pMonitor)
			m_pMonitor->releaseWriter();
	}

	/** Release monitor write access.
	 */
	inline void clear()
	{
		if (m_pMonitor)
		{
			m_pMonitor->releaseWriter();
			m_pMonitor = 0;
		}
	}
};

//----------------------------------------------------------------------------

typedef WriterGuard<QueuedReaderWriterMonitor> QueuedWriterGuard;

//----------------------------------------------------------------------------

} // namespace salhelper

#endif /* !_SALHELPER_MONITOR_HXX_ */