libraries/source/spidermonkey/include-win32-debug/nspr/prcvar.h

   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___ */