1/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
2/* This Source Code Form is subject to the terms of the Mozilla Public
3 * License, v. 2.0. If a copy of the MPL was not distributed with this
4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
5
6#ifndef prcvar_h___
7#define prcvar_h___
8
9#include "prlock.h"
10#include "prinrval.h"
11
12PR_BEGIN_EXTERN_C
13
14typedef struct PRCondVar PRCondVar;
15
16/*
17** Create a new condition variable.
18**
19** "lock" is the lock used to protect the condition variable.
20**
21** Condition variables are synchronization objects that threads can use
22** to wait for some condition to occur.
23**
24** This may fail if memory is tight or if some operating system resource
25** is low. In such cases, a NULL will be returned.
26*/
27NSPR_API(PRCondVar*) PR_NewCondVar(PRLock *lock);
28
29/*
30** Destroy a condition variable. There must be no thread
31** waiting on the condvar. The caller is responsible for guaranteeing
32** that the condvar is no longer in use.
33**
34*/
35NSPR_API(void) PR_DestroyCondVar(PRCondVar *cvar);
36
37/*
38** The thread that waits on a condition is blocked in a "waiting on
39** condition" state until another thread notifies the condition or a
40** caller specified amount of time expires. The lock associated with
41** the condition variable will be released, which must have be held
42** prior to the call to wait.
43**
44** Logically a notified thread is moved from the "waiting on condition"
45** state and made "ready." When scheduled, it will attempt to reacquire
46** the lock that it held when wait was called.
47**
48** The timeout has two well known values, PR_INTERVAL_NO_TIMEOUT and
49** PR_INTERVAL_NO_WAIT. The former value requires that a condition be
50** notified (or the thread interrupted) before it will resume from the
51** wait. If the timeout has a value of PR_INTERVAL_NO_WAIT, the effect
52** is to release the lock, possibly causing a rescheduling within the
53** runtime, then immediately attempting to reacquire the lock and resume.
54**
55** Any other value for timeout will cause the thread to be rescheduled
56** either due to explicit notification or an expired interval. The latter
57** must be determined by treating time as one part of the monitored data
58** being protected by the lock and tested explicitly for an expired
59** interval.
60**
61** Returns PR_FAILURE if the caller has not locked the lock associated
62** with the condition variable or the thread was interrupted (PR_Interrupt()).
63** The particular reason can be extracted with PR_GetError().
64*/
65NSPR_API(PRStatus) PR_WaitCondVar(PRCondVar *cvar, PRIntervalTime timeout);
66
67/*
68** Notify ONE thread that is currently waiting on 'cvar'. Which thread is
69** dependent on the implementation of the runtime. Common sense would dictate
70** that all threads waiting on a single condition have identical semantics,
71** therefore which one gets notified is not significant.
72**
73** The calling thead must hold the lock that protects the condition, as
74** well as the invariants that are tightly bound to the condition, when
75** notify is called.
76**
77** Returns PR_FAILURE if the caller has not locked the lock associated
78** with the condition variable.
79*/
80NSPR_API(PRStatus) PR_NotifyCondVar(PRCondVar *cvar);
81
82/*
83** Notify all of the threads waiting on the condition variable. The order
84** that the threads are notified is indeterminant. The lock that protects
85** the condition must be held.
86**
87** Returns PR_FAILURE if the caller has not locked the lock associated
88** with the condition variable.
89*/
90NSPR_API(PRStatus) PR_NotifyAllCondVar(PRCondVar *cvar);
91
92PR_END_EXTERN_C
93
94#endif /* prcvar_h___ */
95

source code of include/nspr/prcvar.h