wefts_semaphore.h

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/*
   wefts_semaphore.h
   Semaphore object header file.

   $Id: wefts_semaphore.h,v 1.5 2004/03/28 21:45:40 jonnymind Exp $
---------------------------------------
   Begin      : Mon, 08 Mar 2004 21:52:32 +0100
   Author     : Giancarlo Niccolai

   Last modified because:
   Implementing OS independent base threading
*/

/**************************************************************************
*   This program 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 2.1 of the  *
*   License, or (at your option) any later version.                       *
***************************************************************************/

#ifndef WT_SEMAPHORE_H
#define WT_SEMAPHORE_H

#include <wefts_fastcond.h>

namespace Wefts {

class Semaphore: public CleanupHandler
{
private:
   int m_count;
   int m_waiting;
   FastCondition m_cond;
   
public:
   Semaphore( int initial_count = 1 )
   {
      m_count = initial_count;
      m_waiting = 0;
   }
   
   inline int value() { return m_count; }
   
   inline int waiters() { return m_waiting; }
   
   inline void post(int amount=1) {
      m_cond.lock();
      m_count+=amount;
      // todo: would be greatly optimized if signal would not do a broadcast.
      if ( m_waiting > 0 ) 
      {
         if ( m_count == 1 )
            m_cond.signalOne();
         else if ( m_count > 1 )
            m_cond.signal();
      }
      m_cond.unlock();
   }
   
   void wait(CleanupHandler *handler = 0, int position = 0);
      
   bool wait( double seconds, CleanupHandler *handler = 0, int position = 0 );
   
   bool tryWait()
   {
      bool ret;
      m_cond.lock();
      if ( m_count > 0 ) { 
         m_count --;
         ret = true;
      }
      else
         ret = false;
      m_cond.unlock();
      
      return ret;
   }
      
   virtual void handleCleanup( int code, void *caller=0 );  
};

}
#endif
/* end of wefts_semaphore.h */

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