/ray/src/lib/threads/tsemaphore.h

Go to the documentation of this file.

/*
 * lib/threads/tsemaphore.h
 * 
 * Implementing semaphore class for thread synchronisation. 
 * 
 * Copyright (c) 2004 by Wolfgang Wieser ] wwieser (a) gmx <*> de [ 
 * 
 * This file may be distributed and/or modified under the terms of the 
 * GNU General Public License version 2 as published by the Free Software 
 * Foundation. (See COPYING.GPL for details.)
 * 
 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 * 
 */

#ifndef _ThreadLibrary_Semaphore_H_
#define _ThreadLibrary_Semaphore_H_ 1

#include <lib/sconfig.h>    /* MUST be first */

/* Can we use our own pthreads-based implementation? This should be faster.*/
#if USE_PRIVATE__POSIX_SEMAPHORES
#include <errno.h>   /* for EGAGIN */
#include <semaphore.h>
#else
#include <lib/threads/mutex.h>   /* emulate semaphore using mutex */
#include <lib/threads/condition.h>   /* emulate semaphore using mutex */
#endif  /* USE_PRIVATE__POSIX_SEMAPHORES */


class /*_packed_*/ Semaphore
{
    private:
#if USE_PRIVATE__POSIX_SEMAPHORES
        sem_t s;
#else
        ConditionMutex m;
        WaitCondition c;
        volatile int v;    
#endif
        
    public:
        inline Semaphore(int initial_value=0)
#if USE_PRIVATE__POSIX_SEMAPHORES
            {  sem_init(&s,0,initial_value);  }
#else
            : m(),c(),v(initial_value)  { }
#endif
        
        inline ~Semaphore()
#if USE_PRIVATE__POSIX_SEMAPHORES
            {  sem_destroy(&s);  }
#else
            {  /* empty */  }
#endif
        
        /*inline*/ int value()  // inline deliberately commented out (otherwise inlining forced) (WW)
#if USE_PRIVATE__POSIX_SEMAPHORES
            {  int val;  sem_getvalue(&s,&val);  return(val);  }
#else
            {  m.lock();  int val=v;  m.unlock();  return(val);  }
#endif
        
#if USE_PRIVATE__POSIX_SEMAPHORES
        inline void post()  {  sem_post(&s);  }
#else
        void post();  // external
#endif
        
#if USE_PRIVATE__POSIX_SEMAPHORES
        inline void wait()  {  sem_wait(&s);  }
#else
        void wait();  // external
#endif
        
#if USE_PRIVATE__POSIX_SEMAPHORES
        inline bool test()  {  return(sem_trywait(&s)==EAGAIN);  }
#else
        bool test();  // external
#endif
        
};

#endif  /* _ThreadLibrary_Semaphore_H_ */

---