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openflow/usr/include/nspr/prcvar.h

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+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef prcvar_h___
+#define prcvar_h___
+
+#include "prlock.h"
+#include "prinrval.h"
+
+PR_BEGIN_EXTERN_C
+
+typedef struct PRCondVar PRCondVar;
+
+/*
+** Create a new condition variable.
+**
+** 	"lock" is the lock used to protect the condition variable.
+**
+** Condition variables are synchronization objects that threads can use
+** to wait for some condition to occur.
+**
+** This may fail if memory is tight or if some operating system resource
+** is low. In such cases, a NULL will be returned.
+*/
+NSPR_API(PRCondVar*) PR_NewCondVar(PRLock *lock);
+
+/*
+** Destroy a condition variable. There must be no thread
+** waiting on the condvar. The caller is responsible for guaranteeing
+** that the condvar is no longer in use.
+**
+*/
+NSPR_API(void) PR_DestroyCondVar(PRCondVar *cvar);
+
+/*
+** The thread that waits on a condition is blocked in a "waiting on
+** condition" state until another thread notifies the condition or a
+** caller specified amount of time expires. The lock associated with
+** the condition variable will be released, which must have be held
+** prior to the call to wait.
+**
+** Logically a notified thread is moved from the "waiting on condition"
+** state and made "ready." When scheduled, it will attempt to reacquire
+** the lock that it held when wait was called.
+**
+** The timeout has two well known values, PR_INTERVAL_NO_TIMEOUT and
+** PR_INTERVAL_NO_WAIT. The former value requires that a condition be
+** notified (or the thread interrupted) before it will resume from the
+** wait. If the timeout has a value of PR_INTERVAL_NO_WAIT, the effect
+** is to release the lock, possibly causing a rescheduling within the
+** runtime, then immediately attempting to reacquire the lock and resume.
+**
+** Any other value for timeout will cause the thread to be rescheduled
+** either due to explicit notification or an expired interval. The latter
+** must be determined by treating time as one part of the monitored data
+** being protected by the lock and tested explicitly for an expired
+** interval.
+**
+** Returns PR_FAILURE if the caller has not locked the lock associated
+** with the condition variable or the thread was interrupted (PR_Interrupt()).
+** The particular reason can be extracted with PR_GetError().
+*/
+NSPR_API(PRStatus) PR_WaitCondVar(PRCondVar *cvar, PRIntervalTime timeout);
+
+/*
+** Notify ONE thread that is currently waiting on 'cvar'. Which thread is
+** dependent on the implementation of the runtime. Common sense would dictate
+** that all threads waiting on a single condition have identical semantics,
+** therefore which one gets notified is not significant. 
+**
+** The calling thead must hold the lock that protects the condition, as
+** well as the invariants that are tightly bound to the condition, when
+** notify is called.
+**
+** Returns PR_FAILURE if the caller has not locked the lock associated
+** with the condition variable.
+*/
+NSPR_API(PRStatus) PR_NotifyCondVar(PRCondVar *cvar);
+
+/*
+** Notify all of the threads waiting on the condition variable. The order
+** that the threads are notified is indeterminant. The lock that protects
+** the condition must be held.
+**
+** Returns PR_FAILURE if the caller has not locked the lock associated
+** with the condition variable.
+*/
+NSPR_API(PRStatus) PR_NotifyAllCondVar(PRCondVar *cvar);
+
+PR_END_EXTERN_C
+
+#endif /* prcvar_h___ */