PthreadReadWriteLock.h

Go to the documentation of this file.

//=============================================================================
//  PthreadReadWriteLock and protection classes
//-----------------------------------------------------------------------------
//  POSIX Pthread class library
//  Copyright (C) 1997-1999  The University of Texas
//
//  This library is free software; you can redistribute it and/or modify it
//  under the terms of the GNU Library General Public License as published
//  by the Free Software Foundation; either version 2 of the License, or
//  (at your option) any later version.
//
//  This library is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
//  Library General Public License for more details.
//
//  The GNU Public License is available in the file LICENSE, or you
//  can write to the Free Software Foundation, Inc., 59 Temple Place -
//  Suite 330, Boston, MA 02111-1307, USA, or you can find it on the
//  World Wide Web at http://www.fsf.org.
//=============================================================================


#ifndef PthreadReadWriteLock_h
#define PthreadReadWriteLock_h
#pragma once

#include <cpn/common.h>
#include <cpn/threading/PthreadDefs.h>
#ifdef _POSIX_THREADS

#include <cpn/threading/PthreadErrorHandler.h>
#include <cpn/threading/PthreadMutex.h>
#include <cpn/threading/PthreadCondition.h>


class PthreadReadWriteLock : public PthreadErrorHandler {
  public:
    // if (priorityWrites) is true, readers must wait for a pending writer
    // otherwise, the writer must have some lucky timing! 
    PthreadReadWriteLock(int _priorityWrites = 1);
//   ~PthreadReadWriteLock(void);

    void ReadLock(void);
    void WriteLock(void);
    void ReadUnlock(void);
    void WriteUnlock(void);
        
  private:
    PthreadMutex        mutex;
    PthreadCondition    lockFree;
    int                 numReaders;
    int                 writing;
    int                 noNewReaders;
    int                 priorityWrites;
};


class PthreadReadLockProtected {
  public:
    PthreadReadLockProtected(PthreadReadWriteLock& tl): theReadWriteLock(&tl)
                                    { theReadWriteLock->ReadLock(); }
   ~PthreadReadLockProtected(void)  { theReadWriteLock->ReadUnlock(); }
  private:
    PthreadReadWriteLock* theReadWriteLock;
};


class PthreadWriteLockProtected {
  public:
    PthreadWriteLockProtected(PthreadReadWriteLock& tl): theReadWriteLock(&tl)
                                    { theReadWriteLock->WriteLock(); }
   ~PthreadWriteLockProtected(void) { theReadWriteLock->WriteUnlock(); }
  private:
    PthreadReadWriteLock* theReadWriteLock;
};


#endif
#endif