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 prcvar_h___ 36 #define prcvar_h___ 37 38 #include "prlock.h" 39 #include "prinrval.h" 40 41 PR_BEGIN_EXTERN_C 42 43 typedef struct PRCondVar PRCondVar; 44 45 /* 46 ** Create a new condition variable. 47 ** 48 ** "lock" is the lock used to protect the condition variable. 49 ** 50 ** Condition variables are synchronization objects that threads can use 51 ** to wait for some condition to occur. 52 ** 53 ** This may fail if memory is tight or if some operating system resource 54 ** is low. In such cases, a NULL will be returned. 55 */ 56 NSPR_API(PRCondVar*) PR_NewCondVar(PRLock *lock); 57 58 /* 59 ** Destroy a condition variable. There must be no thread 60 ** waiting on the condvar. The caller is responsible for guaranteeing 61 ** that the condvar is no longer in use. 62 ** 63 */ 64 NSPR_API(void) PR_DestroyCondVar(PRCondVar *cvar); 65 66 /* 67 ** The thread that waits on a condition is blocked in a "waiting on 68 ** condition" state until another thread notifies the condition or a 69 ** caller specified amount of time expires. The lock associated with 70 ** the condition variable will be released, which must have be held 71 ** prior to the call to wait. 72 ** 73 ** Logically a notified thread is moved from the "waiting on condition" 74 ** state and made "ready." When scheduled, it will attempt to reacquire 75 ** the lock that it held when wait was called. 76 ** 77 ** The timeout has two well known values, PR_INTERVAL_NO_TIMEOUT and 78 ** PR_INTERVAL_NO_WAIT. The former value requires that a condition be 79 ** notified (or the thread interrupted) before it will resume from the 80 ** wait. If the timeout has a value of PR_INTERVAL_NO_WAIT, the effect 81 ** is to release the lock, possibly causing a rescheduling within the 82 ** runtime, then immediately attempting to reacquire the lock and resume. 83 ** 84 ** Any other value for timeout will cause the thread to be rescheduled 85 ** either due to explicit notification or an expired interval. The latter 86 ** must be determined by treating time as one part of the monitored data 87 ** being protected by the lock and tested explicitly for an expired 88 ** interval. 89 ** 90 ** Returns PR_FAILURE if the caller has not locked the lock associated 91 ** with the condition variable or the thread was interrupted (PR_Interrupt()). 92 ** The particular reason can be extracted with PR_GetError(). 93 */ 94 NSPR_API(PRStatus) PR_WaitCondVar(PRCondVar *cvar, PRIntervalTime timeout); 95 96 /* 97 ** Notify ONE thread that is currently waiting on 'cvar'. Which thread is 98 ** dependent on the implementation of the runtime. Common sense would dictate 99 ** that all threads waiting on a single condition have identical semantics, 100 ** therefore which one gets notified is not significant. 101 ** 102 ** The calling thead must hold the lock that protects the condition, as 103 ** well as the invariants that are tightly bound to the condition, when 104 ** notify is called. 105 ** 106 ** Returns PR_FAILURE if the caller has not locked the lock associated 107 ** with the condition variable. 108 */ 109 NSPR_API(PRStatus) PR_NotifyCondVar(PRCondVar *cvar); 110 111 /* 112 ** Notify all of the threads waiting on the condition variable. The order 113 ** that the threads are notified is indeterminant. The lock that protects 114 ** the condition must be held. 115 ** 116 ** Returns PR_FAILURE if the caller has not locked the lock associated 117 ** with the condition variable. 118 */ 119 NSPR_API(PRStatus) PR_NotifyAllCondVar(PRCondVar *cvar); 120 121 PR_END_EXTERN_C 122 123 #endif /* prcvar_h___ */ 124
