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//

// RWLock.h

//

// $Id: //poco/1.3/Foundation/include/Poco/RWLock.h#1 $

//

// Library: Foundation

// Package: Threading

// Module:  RWLock

//

// Definition of the RWLock class.

//

// 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.

//

#ifndef Foundation_RWLock_INCLUDED

#define Foundation_RWLock_INCLUDED

#include "Poco/Foundation.h"

#include "Poco/Exception.h"

#if defined(POCO_OS_FAMILY_WINDOWS)

#include "Poco/RWLock_WIN32.h"

#else

#include "Poco/RWLock_POSIX.h"

#endif

namespace Poco {

class ScopedRWLock;

class Foundation_API RWLock: private RWLockImpl

        /// A reader writer lock allows multiple concurrent

        /// readers or one exclusive writer.

{

public:

        typedef ScopedRWLock ScopedLock;

        RWLock();

                /// Creates the Reader/Writer lock.

        ~RWLock();

                /// Destroys the Reader/Writer lock.

        void readLock();

                /// Acquires a read lock. If another thread currently holds a write lock,

                /// waits until the write lock is released.

        bool tryReadLock();

                /// Tries to acquire a read lock. Immediately returns true if successful, or

                /// false if another thread currently holds a write lock.

        void writeLock();

                /// Acquires a write lock. If one or more other threads currently hold 

                /// locks, waits until all locks are released. The results are undefined

                /// if the same thread already holds a read or write lock

        bool tryWriteLock();

                /// Tries to acquire a write lock. Immediately returns true if successful,

                /// or false if one or more other threads currently hold 

                /// locks. The result is undefined if the same thread already

                /// holds a read or write lock.

        void unlock();

                /// Releases the read or write lock.

private:

        RWLock(const RWLock&);

        RWLock& operator = (const RWLock&);

};

class Foundation_API ScopedRWLock

        /// A variant of ScopedLock for reader/writer locks.

{

public:

        ScopedRWLock(RWLock& rwl, bool write = false);

        ~ScopedRWLock();

private:

        RWLock& _rwl;

        ScopedRWLock();

        ScopedRWLock(const ScopedRWLock&);

        ScopedRWLock& operator = (const ScopedRWLock&);

};

//

// inlines

//

inline void RWLock::readLock()

{

        readLockImpl();

}

inline bool RWLock::tryReadLock()

{

        return tryReadLockImpl();

}

inline void RWLock::writeLock()

{

        writeLockImpl();

}

inline bool RWLock::tryWriteLock()

{

        return tryWriteLockImpl();

}

inline void RWLock::unlock()

{

        unlockImpl();

}

inline ScopedRWLock::ScopedRWLock(RWLock& rwl, bool write): _rwl(rwl)

{

        if (write)

                _rwl.writeLock();

        else

                _rwl.readLock();

}

inline ScopedRWLock::~ScopedRWLock()

{

        _rwl.unlock();

}

} // namespace Poco

#endif // Foundation_RWLock_INCLUDED