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