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| 1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ |
| 2 /* ***** BEGIN LICENSE BLOCK ***** |
| 3 * Version: MPL 1.1/GPL 2.0/LGPL 2.1 |
| 4 * |
| 5 * The contents of this file are subject to the Mozilla Public License Version |
| 6 * 1.1 (the "License"); you may not use this file except in compliance with |
| 7 * the License. You may obtain a copy of the License at |
| 8 * http://www.mozilla.org/MPL/ |
| 9 * |
| 10 * Software distributed under the License is distributed on an "AS IS" basis, |
| 11 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License |
| 12 * for the specific language governing rights and limitations under the |
| 13 * License. |
| 14 * |
| 15 * The Original Code is the Netscape Portable Runtime (NSPR). |
| 16 * |
| 17 * The Initial Developer of the Original Code is |
| 18 * Netscape Communications Corporation. |
| 19 * Portions created by the Initial Developer are Copyright (C) 1998-2000 |
| 20 * the Initial Developer. All Rights Reserved. |
| 21 * |
| 22 * Contributor(s): |
| 23 * |
| 24 * Alternatively, the contents of this file may be used under the terms of |
| 25 * either the GNU General Public License Version 2 or later (the "GPL"), or |
| 26 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"), |
| 27 * in which case the provisions of the GPL or the LGPL are applicable instead |
| 28 * of those above. If you wish to allow use of your version of this file only |
| 29 * under the terms of either the GPL or the LGPL, and not to allow others to |
| 30 * use your version of this file under the terms of the MPL, indicate your |
| 31 * decision by deleting the provisions above and replace them with the notice |
| 32 * and other provisions required by the GPL or the LGPL. If you do not delete |
| 33 * the provisions above, a recipient may use your version of this file under |
| 34 * the terms of any one of the MPL, the GPL or the LGPL. |
| 35 * |
| 36 * ***** END LICENSE BLOCK ***** */ |
| 37 |
| 38 #ifndef prsem_h___ |
| 39 #define prsem_h___ |
| 40 |
| 41 /* |
| 42 ** API for counting semaphores. Semaphores are counting synchronizing |
| 43 ** variables based on a lock and a condition variable. They are lightweight |
| 44 ** contention control for a given count of resources. |
| 45 */ |
| 46 #include "prtypes.h" |
| 47 |
| 48 PR_BEGIN_EXTERN_C |
| 49 |
| 50 typedef struct PRSemaphore PRSemaphore; |
| 51 |
| 52 /* |
| 53 ** Create a new semaphore object. |
| 54 */ |
| 55 NSPR_API(PRSemaphore*) PR_NewSem(PRUintn value); |
| 56 |
| 57 /* |
| 58 ** Destroy the given semaphore object. |
| 59 ** |
| 60 */ |
| 61 NSPR_API(void) PR_DestroySem(PRSemaphore *sem); |
| 62 |
| 63 /* |
| 64 ** Wait on a Semaphore. |
| 65 ** |
| 66 ** This routine allows a calling thread to wait or proceed depending upon the |
| 67 ** state of the semahore sem. The thread can proceed only if the counter value |
| 68 ** of the semaphore sem is currently greater than 0. If the value of semaphore |
| 69 ** sem is positive, it is decremented by one and the routine returns immediately
|
| 70 ** allowing the calling thread to continue. If the value of semaphore sem is 0, |
| 71 ** the calling thread blocks awaiting the semaphore to be released by another |
| 72 ** thread. |
| 73 ** |
| 74 ** This routine can return PR_PENDING_INTERRUPT if the waiting thread |
| 75 ** has been interrupted. |
| 76 */ |
| 77 NSPR_API(PRStatus) PR_WaitSem(PRSemaphore *sem); |
| 78 |
| 79 /* |
| 80 ** This routine increments the counter value of the semaphore. If other threads |
| 81 ** are blocked for the semaphore, then the scheduler will determine which ONE |
| 82 ** thread will be unblocked. |
| 83 */ |
| 84 NSPR_API(void) PR_PostSem(PRSemaphore *sem); |
| 85 |
| 86 /* |
| 87 ** Returns the value of the semaphore referenced by sem without affecting |
| 88 ** the state of the semaphore. The value represents the semaphore vaule |
| 89 F** at the time of the call, but may not be the actual value when the |
| 90 ** caller inspects it. |
| 91 */ |
| 92 NSPR_API(PRUintn) PR_GetValueSem(PRSemaphore *sem); |
| 93 |
| 94 PR_END_EXTERN_C |
| 95 |
| 96 #endif /* prsem_h___ */ |
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