root/juggler/tags/1.0.5/Sync/vjRWMutex.h

/*************** <auto-copyright.pl BEGIN do not edit this line> **************
 *
 * VR Juggler is (C) Copyright 1998, 1999, 2000 by Iowa State University
 *
 * Original Authors:
 *   Allen Bierbaum, Christopher Just,
 *   Patrick Hartling, Kevin Meinert,
 *   Carolina Cruz-Neira, Albert Baker
 *
 * 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.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * -----------------------------------------------------------------
 * File:          $RCSfile$
 * Date modified: $Date$
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 *************** <auto-copyright.pl END do not edit this line> ***************/


#ifndef _VJRWMutex_h_
#define _VJRWMutex_h_

#include <vjConfig.h>
#include <Sync/vjSemaphore.h>
#include <Sync/vjCond.h>
#include <Sync/vjMutex.h>

//----------------------------------------------
// vjRWMutex
//
// Purpose:
//:    vjRWMutex wrapper
//
//
// Author:
//      Allen Bierbaum
//
// Date: 1-31-97
//-----------------------------------------------
//!PUBLIC_API:
class vjRWMutex
{
public:
    vjRWMutex () : waitingReaders(&stateLock),
        numWaitingReaders(0),
        waitingWriters(&stateLock),
        numWaitingWriters(0),
        refCount(0)
    {}

    ~vjRWMutex(void)
    {}

    //---------------------------------------------------------
    //: Lock the mutex.
    //
    //! RETURNS:  1 - Acquired
    //! RETURNS: -1 - Error
    //---------------------------------------------------------
    int acquire()
    {
        return acquireWrite();
    }

    //----------------------------------------------------------
    //: Acquire a read mutex.
    //----------------------------------------------------------
    int acquireRead(void);

    //----------------------------------------------------------
    //: Acquire a write mutex.
    //----------------------------------------------------------
    int acquireWrite(void);

    //---------------------------------------------------------
    //: Trys to acquire the mutex.
    //  Wait until the semaphore value is greater than 0.
    //  Then decrement by 1 and return.
    //  P operation.
    //
    //! RETURNS: 1 - Acquired
    //! RETURNS: 0 - Not acquired
    //---------------------------------------------------------
    int tryAcquire ()
    {
        return tryAcquireWrite();
    }

    //----------------------------------------------------------
    //: Try to acquire a read mutex.
    //----------------------------------------------------------
    int tryAcquireRead (void);

    //----------------------------------------------------------
    //: Try to acquire a write mutex.
    //----------------------------------------------------------
    int tryAcquireWrite (void);

    //---------------------------------------------------------
    //: Release the mutex.
    //
    //! RETURNS:  0 - Success
    //! RETURNS: -1 - Error
    //---------------------------------------------------------
    int release(void);

    //------------------------------------------------------
    //: Test the current lock status.
    //
    //! RETURNS: 0 - Not locked
    //! RETURNS: 1 - Locked
    //------------------------------------------------------
    int test()
    {
        return stateLock.test();
    }

    //---------------------------------------------------------
    //: Dump the mutex debug stuff and current state.
    //---------------------------------------------------------
    void dump (FILE* dest = stderr,
               const char* message = "\n------ Mutex Dump -----\n") const
    {
        stateLock.dump();
    }

protected:
    vjMutex stateLock;        //: Serialize access to internal state.
    vjCond waitingReaders;    //: Reader threads waiting to acquire the lock.
    int numWaitingReaders;    //: Number of waiting readers.

    vjCond waitingWriters;    //: Writer threads waiting to acquire the lock.
    int numWaitingWriters;    //: Number of waiting writers.

    // Value is -1 if writer has the lock, else this keeps track of the
    // number of readers holding the lock.
    int refCount;

    // = Prevent assignment and initialization.
    void operator= (const vjRWMutex &) {}
    vjRWMutex (const vjRWMutex &) {}
};

#endif