OSX/libsecurity_asn1/lib/prcvar.h

   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
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   9  * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
  10  * implied. See the License for the specific language governing
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  12  *
  13  * The Original Code is the Netscape Portable Runtime (NSPR).
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  15  * The Initial Developer of the Original Code is Netscape
  16  * Communications Corporation.  Portions created by Netscape are
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  24  * "GPL"), in which case the provisions of the GPL are applicable
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  34
  35 #ifndef prcvar_h___
  36 #define prcvar_h___
  37
  38 #include <security_asn1/prlock.h>
  39 #include <security_asn1/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___ */