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RWLock_WIN32.cpp

//
// RWLock_WIN32.cpp
//
// $Id: //poco/1.3/Foundation/src/RWLock_WIN32.cpp#2 $
//
// Library: Foundation
// Package: Threading
// Module:  RWLock
//
// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:
// 
// The copyright notices in the Software and this entire statement, including
// the above license grant, this restriction and the following disclaimer,
// must be included in all copies of the Software, in whole or in part, and
// all derivative works of the Software, unless such copies or derivative
// works are solely in the form of machine-executable object code generated by
// a source language processor.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//


#include "Poco/RWLock_WIN32.h"


namespace Poco {


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

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

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


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


inline void RWLockImpl::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 RWLockImpl::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 RWLockImpl::readLockImpl()
{
      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 RWLockImpl::tryReadLockImpl()
{
      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 RWLockImpl::writeLockImpl()
{
      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 RWLockImpl::tryWriteLockImpl()
{
      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 RWLockImpl::unlockImpl()
{
      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");
      }
}


} // namespace Poco

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