Line data    Source code

       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          29 : 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           1 : 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          32 : 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           0 : 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         105 : NSPR_API(PRStatus) PR_NotifyAllCondVar(PRCondVar *cvar);
      91             : 
      92             : PR_END_EXTERN_C
      93             : 
      94             : #endif /* prcvar_h___ */