rwlock_win32.cpp

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//
// RWLock_WIN32.cpp
//
// $Id: //poco/Main/Foundation/src/RWLock_WIN32.cpp#5 $
//
// Copyright (c) 2004, Guenter Obiltschnig/Applied Informatics.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
//
// 3. Redistributions in any form must be accompanied by information on
//    how to obtain complete source code for this software and any
//    accompanying software that uses this software.  The source code
//    must either be included in the distribution or be available for no
//    more than the cost of distribution plus a nominal fee, and must be
//    freely redistributable under reasonable conditions.  For an
//    executable file, complete source code means the source code for all
//    modules it contains.  It does not include source code for modules or
//    files that typically accompany the major components of the operating
//    system on which the executable file runs.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
// ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
//


#include "Foundation/RWLock_WIN32.h"


Foundation_BEGIN


RWLockImp::RWLockImp(): _readers(0), _writers(0)
{
	_mutex = CreateMutex(NULL, FALSE, NULL);
	if (_mutex == NULL)
		throw SystemException("cannot create reader/writer lock");

	_readEvent = CreateEvent(NULL, TRUE, TRUE, NULL);
	if (_readEvent == NULL)
		throw SystemException("cannot create reader/writer lock");

	_writeEvent = CreateEvent(NULL, TRUE, TRUE, NULL);
	if (_writeEvent == NULL)
		throw SystemException("cannot create reader/writer lock");
}


RWLockImp::~RWLockImp()
{
	CloseHandle(_mutex);
	CloseHandle(_readEvent);
	CloseHandle(_writeEvent);
}


inline void RWLockImp::addWriter()
{
	switch (WaitForSingleObject(_mutex, INFINITE))
	{
	case WAIT_OBJECT_0:
		if (++_writers == 1) ResetEvent(_readEvent);
		ReleaseMutex(_mutex);
		break;
	default:
		throw SystemException("cannot lock reader/writer lock");
	}
}


inline void RWLockImp::removeWriter()
{
	switch (WaitForSingleObject(_mutex, INFINITE))
	{
	case WAIT_OBJECT_0:
		if (--_writers == 0) SetEvent(_readEvent);
		ReleaseMutex(_mutex);
		break;
	default:
		throw SystemException("cannot lock reader/writer lock");
	}
}


void RWLockImp::readLockImp()
{
	HANDLE h[2];
	h[0] = _mutex;
	h[1] = _readEvent;
	switch (WaitForMultipleObjects(2, h, TRUE, INFINITE))
	{
	case WAIT_OBJECT_0:
	case WAIT_OBJECT_0 + 1:
		++_readers;
		ResetEvent(_writeEvent);
		ReleaseMutex(_mutex);
		break;
	default:
		throw SystemException("cannot lock reader/writer lock");
	}
}


bool RWLockImp::tryReadLockImp()
{
	HANDLE h[2];
	h[0] = _mutex;
	h[1] = _readEvent;
	switch (WaitForMultipleObjects(2, h, TRUE, 1))
	{
	case WAIT_OBJECT_0:
	case WAIT_OBJECT_0 + 1:
		++_readers;
		ResetEvent(_writeEvent);
		ReleaseMutex(_mutex);
		return true;
	case WAIT_TIMEOUT:
		return false;
	default:
		throw SystemException("cannot lock reader/writer lock");
	}
}


void RWLockImp::writeLockImp()
{
	addWriter();
	HANDLE h[2];
	h[0] = _mutex;
	h[1] = _writeEvent;
	switch (WaitForMultipleObjects(2, h, TRUE, INFINITE))
	{
	case WAIT_OBJECT_0:
	case WAIT_OBJECT_0 + 1:
		--_writers;
		++_readers;
		ResetEvent(_readEvent);
		ResetEvent(_writeEvent);
		ReleaseMutex(_mutex);
		break;
	default:
		removeWriter();
		throw SystemException("cannot lock reader/writer lock");
	}
}


bool RWLockImp::tryWriteLockImp()
{
	addWriter();
	HANDLE h[2];
	h[0] = _mutex;
	h[1] = _writeEvent;
	switch (WaitForMultipleObjects(2, h, TRUE, 1))
	{
	case WAIT_OBJECT_0:
	case WAIT_OBJECT_0 + 1:
		--_writers;
		++_readers;
		ResetEvent(_readEvent);
		ResetEvent(_writeEvent);
		ReleaseMutex(_mutex);
		return true;
	case WAIT_TIMEOUT:
		removeWriter();
		return false;
	default:
		removeWriter();
		throw SystemException("cannot lock reader/writer lock");
	}
}


void RWLockImp::unlockImp()
{
	switch (WaitForSingleObject(_mutex, INFINITE))
	{
	case WAIT_OBJECT_0:
		if (_writers == 0) SetEvent(_readEvent);
		if (--_readers == 0) SetEvent(_writeEvent);
		ReleaseMutex(_mutex);
		break;
	default:
		throw SystemException("cannot unlock reader/writer lock");
	}
}


Foundation_END