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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
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 * http://www.mozilla.org/MPL/
 * Software distributed under the License is distributed on an "AS IS" basis,
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 * for the specific language governing rights and limitations under the
 * License.
 * The Original Code is the Netscape Portable Runtime (NSPR).
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
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#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"


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);


#endif /* prsem_h___ */

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