1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ 2 /* 3 * The contents of this file are subject to the Mozilla Public 4 * License Version 1.1 (the "License"); you may not use this file 5 * except in compliance with the License. You may obtain a copy of 6 * the License at http://www.mozilla.org/MPL/ 7 * 8 * Software distributed under the License is distributed on an "AS 9 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or 10 * implied. See the License for the specific language governing 11 * rights and limitations under the License. 12 * 13 * The Original Code is the Netscape Portable Runtime (NSPR). 14 * 15 * The Initial Developer of the Original Code is Netscape 16 * Communications Corporation. Portions created by Netscape are 17 * Copyright (C) 1998-2000 Netscape Communications Corporation. All 18 * Rights Reserved. 19 * 20 * Contributor(s): 21 * 22 * Alternatively, the contents of this file may be used under the 23 * terms of the GNU General Public License Version 2 or later (the 24 * "GPL"), in which case the provisions of the GPL are applicable 25 * instead of those above. If you wish to allow use of your 26 * version of this file only under the terms of the GPL and not to 27 * allow others to use your version of this file under the MPL, 28 * indicate your decision by deleting the provisions above and 29 * replace them with the notice and other provisions required by 30 * the GPL. If you do not delete the provisions above, a recipient 31 * may use your version of this file under either the MPL or the 32 * GPL. 33 */ 34 35 #ifndef prsem_h___ 36 #define prsem_h___ 37 38 /* 39 ** API for counting semaphores. Semaphores are counting synchronizing 40 ** variables based on a lock and a condition variable. They are lightweight 41 ** contention control for a given count of resources. 42 */ 43 #include "prtypes.h" 44 45 PR_BEGIN_EXTERN_C 46 47 typedef struct PRSemaphore PRSemaphore; 48 49 /* 50 ** Create a new semaphore object. 51 */ 52 NSPR_API(PRSemaphore*) PR_NewSem(PRUintn value); 53 54 /* 55 ** Destroy the given semaphore object. 56 ** 57 */ 58 NSPR_API(void) PR_DestroySem(PRSemaphore *sem); 59 60 /* 61 ** Wait on a Semaphore. 62 ** 63 ** This routine allows a calling thread to wait or proceed depending upon the 64 ** state of the semahore sem. The thread can proceed only if the counter value 65 ** of the semaphore sem is currently greater than 0. If the value of semaphore 66 ** sem is positive, it is decremented by one and the routine returns immediately 67 ** allowing the calling thread to continue. If the value of semaphore sem is 0, 68 ** the calling thread blocks awaiting the semaphore to be released by another 69 ** thread. 70 ** 71 ** This routine can return PR_PENDING_INTERRUPT if the waiting thread 72 ** has been interrupted. 73 */ 74 NSPR_API(PRStatus) PR_WaitSem(PRSemaphore *sem); 75 76 /* 77 ** This routine increments the counter value of the semaphore. If other threads 78 ** are blocked for the semaphore, then the scheduler will determine which ONE 79 ** thread will be unblocked. 80 */ 81 NSPR_API(void) PR_PostSem(PRSemaphore *sem); 82 83 /* 84 ** Returns the value of the semaphore referenced by sem without affecting 85 ** the state of the semaphore. The value represents the semaphore vaule 86 F** at the time of the call, but may not be the actual value when the 87 ** caller inspects it. 88 */ 89 NSPR_API(PRUintn) PR_GetValueSem(PRSemaphore *sem); 90 91 PR_END_EXTERN_C 92 93 #endif /* prsem_h___ */ 94
