michael@0: /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef prcvar_h___
michael@0: #define prcvar_h___
michael@0: 
michael@0: #include "prlock.h"
michael@0: #include "prinrval.h"
michael@0: 
michael@0: PR_BEGIN_EXTERN_C
michael@0: 
michael@0: typedef struct PRCondVar PRCondVar;
michael@0: 
michael@0: /*
michael@0: ** Create a new condition variable.
michael@0: **
michael@0: ** 	"lock" is the lock used to protect the condition variable.
michael@0: **
michael@0: ** Condition variables are synchronization objects that threads can use
michael@0: ** to wait for some condition to occur.
michael@0: **
michael@0: ** This may fail if memory is tight or if some operating system resource
michael@0: ** is low. In such cases, a NULL will be returned.
michael@0: */
michael@0: NSPR_API(PRCondVar*) PR_NewCondVar(PRLock *lock);
michael@0: 
michael@0: /*
michael@0: ** Destroy a condition variable. There must be no thread
michael@0: ** waiting on the condvar. The caller is responsible for guaranteeing
michael@0: ** that the condvar is no longer in use.
michael@0: **
michael@0: */
michael@0: NSPR_API(void) PR_DestroyCondVar(PRCondVar *cvar);
michael@0: 
michael@0: /*
michael@0: ** The thread that waits on a condition is blocked in a "waiting on
michael@0: ** condition" state until another thread notifies the condition or a
michael@0: ** caller specified amount of time expires. The lock associated with
michael@0: ** the condition variable will be released, which must have be held
michael@0: ** prior to the call to wait.
michael@0: **
michael@0: ** Logically a notified thread is moved from the "waiting on condition"
michael@0: ** state and made "ready." When scheduled, it will attempt to reacquire
michael@0: ** the lock that it held when wait was called.
michael@0: **
michael@0: ** The timeout has two well known values, PR_INTERVAL_NO_TIMEOUT and
michael@0: ** PR_INTERVAL_NO_WAIT. The former value requires that a condition be
michael@0: ** notified (or the thread interrupted) before it will resume from the
michael@0: ** wait. If the timeout has a value of PR_INTERVAL_NO_WAIT, the effect
michael@0: ** is to release the lock, possibly causing a rescheduling within the
michael@0: ** runtime, then immediately attempting to reacquire the lock and resume.
michael@0: **
michael@0: ** Any other value for timeout will cause the thread to be rescheduled
michael@0: ** either due to explicit notification or an expired interval. The latter
michael@0: ** must be determined by treating time as one part of the monitored data
michael@0: ** being protected by the lock and tested explicitly for an expired
michael@0: ** interval.
michael@0: **
michael@0: ** Returns PR_FAILURE if the caller has not locked the lock associated
michael@0: ** with the condition variable or the thread was interrupted (PR_Interrupt()).
michael@0: ** The particular reason can be extracted with PR_GetError().
michael@0: */
michael@0: NSPR_API(PRStatus) PR_WaitCondVar(PRCondVar *cvar, PRIntervalTime timeout);
michael@0: 
michael@0: /*
michael@0: ** Notify ONE thread that is currently waiting on 'cvar'. Which thread is
michael@0: ** dependent on the implementation of the runtime. Common sense would dictate
michael@0: ** that all threads waiting on a single condition have identical semantics,
michael@0: ** therefore which one gets notified is not significant. 
michael@0: **
michael@0: ** The calling thead must hold the lock that protects the condition, as
michael@0: ** well as the invariants that are tightly bound to the condition, when
michael@0: ** notify is called.
michael@0: **
michael@0: ** Returns PR_FAILURE if the caller has not locked the lock associated
michael@0: ** with the condition variable.
michael@0: */
michael@0: NSPR_API(PRStatus) PR_NotifyCondVar(PRCondVar *cvar);
michael@0: 
michael@0: /*
michael@0: ** Notify all of the threads waiting on the condition variable. The order
michael@0: ** that the threads are notified is indeterminant. The lock that protects
michael@0: ** the condition must be held.
michael@0: **
michael@0: ** Returns PR_FAILURE if the caller has not locked the lock associated
michael@0: ** with the condition variable.
michael@0: */
michael@0: NSPR_API(PRStatus) PR_NotifyAllCondVar(PRCondVar *cvar);
michael@0: 
michael@0: PR_END_EXTERN_C
michael@0: 
michael@0: #endif /* prcvar_h___ */