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/* $Id: semaphore.hh,v 1.1 2008-04-28 20:29:15 sybreon Exp $

**

** AEMB2 HI-PERFORMANCE CPU

** Copyright (C) 2004-2007 Shawn Tan Ser Ngiap 

**

** This file is part of AEMB.

**

** AEMB is free software: you can redistribute it and/or modify it

** under the terms of the GNU General Public License as published by

** the Free Software Foundation, either version 3 of the License, or

** (at your option) any later version.

**

** AEMB 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 General Public

** License for more details.

**

** You should have received a copy of the GNU General Public License

** along with AEMB.  If not, see .

*/

/**

   General semaphore library

   @file semaphore.hh

 */

#include "aemb/thread.hh"

#ifndef _AEMB_SEMAPHORE_HH

#define _AEMB_SEMAPHORE_HH

#ifdef __cplusplus

extern "C" {

#endif

  // TODO: Extend this library to include threading mechanisms such as

  // semaphores, mutexes and such.

  /**

     Semaphore struct.

     Presently implemented as software solution but a hardware one may be

     required as the threads are hardware.

  */

  typedef int semaphore;

  /**

     Software Semaphore Signal.

     Increment the semaphore and run. This is a software mechanism.

  */

  inline void aembSignal(volatile semaphore _sem)

  {

    _aembLockMTX();

    _sem++;

    _aembFreeMTX();

  }

  /**

     Software Semaphore Wait.

     Decrement the semaphore and block if < 0. This is a software

     mechanism.

  */

  inline void aembWait(volatile semaphore _sem)

  {

    _aembLockMTX();

    _sem--;

    _aembFreeMTX();

    while (_sem < 0);

  }

  semaphore __mutex_rendezvous0 = 0; ///< internal rendezvous mutex

  semaphore __mutex_rendezvous1 = 1; ///< internal rendezvous mutex

  /**

     Implements a simple rendezvous mechanism

   */

  /*

  inline void aembRendezvous()

  {

    if (isThread1())

      {

        wait(__mutex_rendezvous0);

        signal(__mutex_rendezvous1);

      }

    else

      {

        signal(__mutex_rendezvous0);

        wait(__mutex_rendezvous1);

      }

  }

  */

#ifdef __cplusplus

}

#endif

#endif

/*

$log$

*/