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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 prcvar_h___ |
| 39 #define prcvar_h___ |
| 40 |
| 41 #include "prlock.h" |
| 42 #include "prinrval.h" |
| 43 |
| 44 PR_BEGIN_EXTERN_C |
| 45 |
| 46 typedef struct PRCondVar PRCondVar; |
| 47 |
| 48 /* |
| 49 ** Create a new condition variable. |
| 50 ** |
| 51 ** "lock" is the lock used to protect the condition variable. |
| 52 ** |
| 53 ** Condition variables are synchronization objects that threads can use |
| 54 ** to wait for some condition to occur. |
| 55 ** |
| 56 ** This may fail if memory is tight or if some operating system resource |
| 57 ** is low. In such cases, a NULL will be returned. |
| 58 */ |
| 59 NSPR_API(PRCondVar*) PR_NewCondVar(PRLock *lock); |
| 60 |
| 61 /* |
| 62 ** Destroy a condition variable. There must be no thread |
| 63 ** waiting on the condvar. The caller is responsible for guaranteeing |
| 64 ** that the condvar is no longer in use. |
| 65 ** |
| 66 */ |
| 67 NSPR_API(void) PR_DestroyCondVar(PRCondVar *cvar); |
| 68 |
| 69 /* |
| 70 ** The thread that waits on a condition is blocked in a "waiting on |
| 71 ** condition" state until another thread notifies the condition or a |
| 72 ** caller specified amount of time expires. The lock associated with |
| 73 ** the condition variable will be released, which must have be held |
| 74 ** prior to the call to wait. |
| 75 ** |
| 76 ** Logically a notified thread is moved from the "waiting on condition" |
| 77 ** state and made "ready." When scheduled, it will attempt to reacquire |
| 78 ** the lock that it held when wait was called. |
| 79 ** |
| 80 ** The timeout has two well known values, PR_INTERVAL_NO_TIMEOUT and |
| 81 ** PR_INTERVAL_NO_WAIT. The former value requires that a condition be |
| 82 ** notified (or the thread interrupted) before it will resume from the |
| 83 ** wait. If the timeout has a value of PR_INTERVAL_NO_WAIT, the effect |
| 84 ** is to release the lock, possibly causing a rescheduling within the |
| 85 ** runtime, then immediately attempting to reacquire the lock and resume. |
| 86 ** |
| 87 ** Any other value for timeout will cause the thread to be rescheduled |
| 88 ** either due to explicit notification or an expired interval. The latter |
| 89 ** must be determined by treating time as one part of the monitored data |
| 90 ** being protected by the lock and tested explicitly for an expired |
| 91 ** interval. |
| 92 ** |
| 93 ** Returns PR_FAILURE if the caller has not locked the lock associated |
| 94 ** with the condition variable or the thread was interrupted (PR_Interrupt()). |
| 95 ** The particular reason can be extracted with PR_GetError(). |
| 96 */ |
| 97 NSPR_API(PRStatus) PR_WaitCondVar(PRCondVar *cvar, PRIntervalTime timeout); |
| 98 |
| 99 /* |
| 100 ** Notify ONE thread that is currently waiting on 'cvar'. Which thread is |
| 101 ** dependent on the implementation of the runtime. Common sense would dictate |
| 102 ** that all threads waiting on a single condition have identical semantics, |
| 103 ** therefore which one gets notified is not significant. |
| 104 ** |
| 105 ** The calling thead must hold the lock that protects the condition, as |
| 106 ** well as the invariants that are tightly bound to the condition, when |
| 107 ** notify is called. |
| 108 ** |
| 109 ** Returns PR_FAILURE if the caller has not locked the lock associated |
| 110 ** with the condition variable. |
| 111 */ |
| 112 NSPR_API(PRStatus) PR_NotifyCondVar(PRCondVar *cvar); |
| 113 |
| 114 /* |
| 115 ** Notify all of the threads waiting on the condition variable. The order |
| 116 ** that the threads are notified is indeterminant. The lock that protects |
| 117 ** the condition must be held. |
| 118 ** |
| 119 ** Returns PR_FAILURE if the caller has not locked the lock associated |
| 120 ** with the condition variable. |
| 121 */ |
| 122 NSPR_API(PRStatus) PR_NotifyAllCondVar(PRCondVar *cvar); |
| 123 |
| 124 PR_END_EXTERN_C |
| 125 |
| 126 #endif /* prcvar_h___ */ |
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