prsem.h (2047B)
1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ 2 /* This Source Code Form is subject to the terms of the Mozilla Public 3 * License, v. 2.0. If a copy of the MPL was not distributed with this 4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ 5 6 #ifndef prsem_h___ 7 #define prsem_h___ 8 9 /* 10 ** API for counting semaphores. Semaphores are counting synchronizing 11 ** variables based on a lock and a condition variable. They are lightweight 12 ** contention control for a given count of resources. 13 */ 14 #include "prtypes.h" 15 16 PR_BEGIN_EXTERN_C 17 18 typedef struct PRSemaphore PRSemaphore; 19 20 /* 21 ** Create a new semaphore object. 22 */ 23 NSPR_API(PRSemaphore*) PR_NewSem(PRUintn value); 24 25 /* 26 ** Destroy the given semaphore object. 27 ** 28 */ 29 NSPR_API(void) PR_DestroySem(PRSemaphore *sem); 30 31 /* 32 ** Wait on a Semaphore. 33 ** 34 ** This routine allows a calling thread to wait or proceed depending upon the 35 ** state of the semahore sem. The thread can proceed only if the counter value 36 ** of the semaphore sem is currently greater than 0. If the value of semaphore 37 ** sem is positive, it is decremented by one and the routine returns immediately 38 ** allowing the calling thread to continue. If the value of semaphore sem is 0, 39 ** the calling thread blocks awaiting the semaphore to be released by another 40 ** thread. 41 ** 42 ** This routine can return PR_PENDING_INTERRUPT if the waiting thread 43 ** has been interrupted. 44 */ 45 NSPR_API(PRStatus) PR_WaitSem(PRSemaphore *sem); 46 47 /* 48 ** This routine increments the counter value of the semaphore. If other threads 49 ** are blocked for the semaphore, then the scheduler will determine which ONE 50 ** thread will be unblocked. 51 */ 52 NSPR_API(void) PR_PostSem(PRSemaphore *sem); 53 54 /* 55 ** Returns the value of the semaphore referenced by sem without affecting 56 ** the state of the semaphore. The value represents the semaphore vaule 57 F** at the time of the call, but may not be the actual value when the 58 ** caller inspects it. 59 */ 60 NSPR_API(PRUintn) PR_GetValueSem(PRSemaphore *sem); 61 62 PR_END_EXTERN_C 63 64 #endif /* prsem_h___ */