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btsem.c

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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 * The Original Code is the Netscape Portable Runtime (NSPR).
 *
 * The Initial Developer of the Original Code is
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 * the Initial Developer. All Rights Reserved.
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#include <kernel/OS.h>

#include "primpl.h"

/*
** Create a new semaphore object.
*/
PR_IMPLEMENT(PRSemaphore*)
    PR_NewSem (PRUintn value)
{
      PRSemaphore *semaphore;

      if (!_pr_initialized) _PR_ImplicitInitialization();

      semaphore = PR_NEWZAP(PRSemaphore);
      if (NULL != semaphore) {
            if ((semaphore->sem = create_sem(value, "nspr_sem")) < B_NO_ERROR)
                  return NULL;
            else 
                  return semaphore;
      }
      return NULL;
}

/*
** Destroy the given semaphore object.
**
*/
PR_IMPLEMENT(void)
    PR_DestroySem (PRSemaphore *sem)
{
      status_t result;

      PR_ASSERT(sem != NULL);
      result = delete_sem(sem->sem);
      PR_ASSERT(result == B_NO_ERROR);
      PR_DELETE(sem);
} 

/*
** Wait on a Semaphore.
** 
** This routine allows a calling thread to wait or proceed depending upon
** the state of the semahore sem. The thread can proceed only if the
** counter value of the semaphore sem is currently greater than 0. If the
** value of semaphore sem is positive, it is decremented by one and the
** routine returns immediately allowing the calling thread to continue. If
** the value of semaphore sem is 0, the calling thread blocks awaiting the
** semaphore to be released by another thread.
** 
** This routine can return PR_PENDING_INTERRUPT if the waiting thread 
** has been interrupted.
*/
PR_IMPLEMENT(PRStatus)
    PR_WaitSem (PRSemaphore *sem)
{
      PR_ASSERT(sem != NULL);
      if (acquire_sem(sem->sem) == B_NO_ERROR)
            return PR_SUCCESS;
      else
            return PR_FAILURE;
}

/*
** This routine increments the counter value of the semaphore. If other
** threads are blocked for the semaphore, then the scheduler will
** determine which ONE thread will be unblocked.
*/
PR_IMPLEMENT(void)
    PR_PostSem (PRSemaphore *sem)
{
      status_t result;

      PR_ASSERT(sem != NULL);
      result = release_sem(sem->sem);
      PR_ASSERT(result == B_NO_ERROR);
}

/*
** Returns the value of the semaphore referenced by sem without affecting
** the state of the semaphore.  The value represents the semaphore value
** at the time of the call, but may not be the actual value when the
** caller inspects it.
*/
PR_IMPLEMENT(PRUintn)
    PR_GetValueSem (PRSemaphore *sem)
{
      sem_info    info;

      PR_ASSERT(sem != NULL);
      get_sem_info(sem->sem, &info);
      return info.count;
}

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