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comparison: nsprpub/pr/include/prcvar.h
nsprpub/pr/include/prcvar.h
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| 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 prcvar_h___ | |
| 7 #define prcvar_h___ | |
| 8 | |
| 9 #include "prlock.h" | |
| 10 #include "prinrval.h" | |
| 11 | |
| 12 PR_BEGIN_EXTERN_C | |
| 13 | |
| 14 typedef struct PRCondVar PRCondVar; | |
| 15 | |
| 16 /* | |
| 17 ** Create a new condition variable. | |
| 18 ** | |
| 19 ** "lock" is the lock used to protect the condition variable. | |
| 20 ** | |
| 21 ** Condition variables are synchronization objects that threads can use | |
| 22 ** to wait for some condition to occur. | |
| 23 ** | |
| 24 ** This may fail if memory is tight or if some operating system resource | |
| 25 ** is low. In such cases, a NULL will be returned. | |
| 26 */ | |
| 27 NSPR_API(PRCondVar*) PR_NewCondVar(PRLock *lock); | |
| 28 | |
| 29 /* | |
| 30 ** Destroy a condition variable. There must be no thread | |
| 31 ** waiting on the condvar. The caller is responsible for guaranteeing | |
| 32 ** that the condvar is no longer in use. | |
| 33 ** | |
| 34 */ | |
| 35 NSPR_API(void) PR_DestroyCondVar(PRCondVar *cvar); | |
| 36 | |
| 37 /* | |
| 38 ** The thread that waits on a condition is blocked in a "waiting on | |
| 39 ** condition" state until another thread notifies the condition or a | |
| 40 ** caller specified amount of time expires. The lock associated with | |
| 41 ** the condition variable will be released, which must have be held | |
| 42 ** prior to the call to wait. | |
| 43 ** | |
| 44 ** Logically a notified thread is moved from the "waiting on condition" | |
| 45 ** state and made "ready." When scheduled, it will attempt to reacquire | |
| 46 ** the lock that it held when wait was called. | |
| 47 ** | |
| 48 ** The timeout has two well known values, PR_INTERVAL_NO_TIMEOUT and | |
| 49 ** PR_INTERVAL_NO_WAIT. The former value requires that a condition be | |
| 50 ** notified (or the thread interrupted) before it will resume from the | |
| 51 ** wait. If the timeout has a value of PR_INTERVAL_NO_WAIT, the effect | |
| 52 ** is to release the lock, possibly causing a rescheduling within the | |
| 53 ** runtime, then immediately attempting to reacquire the lock and resume. | |
| 54 ** | |
| 55 ** Any other value for timeout will cause the thread to be rescheduled | |
| 56 ** either due to explicit notification or an expired interval. The latter | |
| 57 ** must be determined by treating time as one part of the monitored data | |
| 58 ** being protected by the lock and tested explicitly for an expired | |
| 59 ** interval. | |
| 60 ** | |
| 61 ** Returns PR_FAILURE if the caller has not locked the lock associated | |
| 62 ** with the condition variable or the thread was interrupted (PR_Interrupt()). | |
| 63 ** The particular reason can be extracted with PR_GetError(). | |
| 64 */ | |
| 65 NSPR_API(PRStatus) PR_WaitCondVar(PRCondVar *cvar, PRIntervalTime timeout); | |
| 66 | |
| 67 /* | |
| 68 ** Notify ONE thread that is currently waiting on 'cvar'. Which thread is | |
| 69 ** dependent on the implementation of the runtime. Common sense would dictate | |
| 70 ** that all threads waiting on a single condition have identical semantics, | |
| 71 ** therefore which one gets notified is not significant. | |
| 72 ** | |
| 73 ** The calling thead must hold the lock that protects the condition, as | |
| 74 ** well as the invariants that are tightly bound to the condition, when | |
| 75 ** notify is called. | |
| 76 ** | |
| 77 ** Returns PR_FAILURE if the caller has not locked the lock associated | |
| 78 ** with the condition variable. | |
| 79 */ | |
| 80 NSPR_API(PRStatus) PR_NotifyCondVar(PRCondVar *cvar); | |
| 81 | |
| 82 /* | |
| 83 ** Notify all of the threads waiting on the condition variable. The order | |
| 84 ** that the threads are notified is indeterminant. The lock that protects | |
| 85 ** the condition must be held. | |
| 86 ** | |
| 87 ** Returns PR_FAILURE if the caller has not locked the lock associated | |
| 88 ** with the condition variable. | |
| 89 */ | |
| 90 NSPR_API(PRStatus) PR_NotifyAllCondVar(PRCondVar *cvar); | |
| 91 | |
| 92 PR_END_EXTERN_C | |
| 93 | |
| 94 #endif /* prcvar_h___ */ |
