text: /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
  /* This Source Code Form is subject to the terms of the Mozilla Public
   * License, v. 2.0. If a copy of the MPL was not distributed with this
   * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
  
  #ifndef prsem_h___
  #define prsem_h___
  
  /*
  ** API for counting semaphores. Semaphores are counting synchronizing
  ** variables based on a lock and a condition variable.  They are lightweight
  ** contention control for a given count of resources.
  */
  #include "prtypes.h"
  
  PR_BEGIN_EXTERN_C
  
  typedef struct PRSemaphore PRSemaphore;
  
  /*
  ** Create a new semaphore object.
  */
  NSPR_API(PRSemaphore*) PR_NewSem(PRUintn value);
  
  /*
  ** Destroy the given semaphore object.
  **
  */
  NSPR_API(void) PR_DestroySem(PRSemaphore *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.
  */
  NSPR_API(PRStatus) PR_WaitSem(PRSemaphore *sem);
  
  /*
  ** 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.
  */
  NSPR_API(void) PR_PostSem(PRSemaphore *sem);
  
  /*
  ** Returns the value of the semaphore referenced by sem without affecting
  ** the state of the semaphore.  The value represents the semaphore vaule
  F** at the time of the call, but may not be the actual value when the
  ** caller inspects it.
  */
  NSPR_API(PRUintn) PR_GetValueSem(PRSemaphore *sem);
  
  PR_END_EXTERN_C
  
  #endif /* prsem_h___ */
  