prcvar.h   [plain text]

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#ifndef prcvar_h___
#define prcvar_h___

#include <security_asn1/prlock.h>
#include <security_asn1/prinrval.h>


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);


#endif /* prcvar_h___ */