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1.1 root 1: /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
2: /*
3: * The contents of this file are subject to the Mozilla Public
4: * License Version 1.1 (the "License"); you may not use this file
5: * except in compliance with the License. You may obtain a copy of
6: * the License at http://www.mozilla.org/MPL/
7: *
8: * Software distributed under the License is distributed on an "AS
9: * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
10: * implied. See the License for the specific language governing
11: * rights and limitations under the License.
12: *
13: * The Original Code is the Netscape Portable Runtime (NSPR).
14: *
15: * The Initial Developer of the Original Code is Netscape
16: * Communications Corporation. Portions created by Netscape are
17: * Copyright (C) 1998-2000 Netscape Communications Corporation. All
18: * Rights Reserved.
19: *
20: * Contributor(s):
21: *
22: * Alternatively, the contents of this file may be used under the
23: * terms of the GNU General Public License Version 2 or later (the
24: * "GPL"), in which case the provisions of the GPL are applicable
25: * instead of those above. If you wish to allow use of your
26: * version of this file only under the terms of the GPL and not to
27: * allow others to use your version of this file under the MPL,
28: * indicate your decision by deleting the provisions above and
29: * replace them with the notice and other provisions required by
30: * the GPL. If you do not delete the provisions above, a recipient
31: * may use your version of this file under either the MPL or the
32: * GPL.
33: */
34:
35: #ifndef prcvar_h___
36: #define prcvar_h___
37:
38: #include "prlock.h"
39: #include "prinrval.h"
40:
41: PR_BEGIN_EXTERN_C
42:
43: typedef struct PRCondVar PRCondVar;
44:
45: /*
46: ** Create a new condition variable.
47: **
48: ** "lock" is the lock used to protect the condition variable.
49: **
50: ** Condition variables are synchronization objects that threads can use
51: ** to wait for some condition to occur.
52: **
53: ** This may fail if memory is tight or if some operating system resource
54: ** is low. In such cases, a NULL will be returned.
55: */
56: NSPR_API(PRCondVar*) PR_NewCondVar(PRLock *lock);
57:
58: /*
59: ** Destroy a condition variable. There must be no thread
60: ** waiting on the condvar. The caller is responsible for guaranteeing
61: ** that the condvar is no longer in use.
62: **
63: */
64: NSPR_API(void) PR_DestroyCondVar(PRCondVar *cvar);
65:
66: /*
67: ** The thread that waits on a condition is blocked in a "waiting on
68: ** condition" state until another thread notifies the condition or a
69: ** caller specified amount of time expires. The lock associated with
70: ** the condition variable will be released, which must have be held
71: ** prior to the call to wait.
72: **
73: ** Logically a notified thread is moved from the "waiting on condition"
74: ** state and made "ready." When scheduled, it will attempt to reacquire
75: ** the lock that it held when wait was called.
76: **
77: ** The timeout has two well known values, PR_INTERVAL_NO_TIMEOUT and
78: ** PR_INTERVAL_NO_WAIT. The former value requires that a condition be
79: ** notified (or the thread interrupted) before it will resume from the
80: ** wait. If the timeout has a value of PR_INTERVAL_NO_WAIT, the effect
81: ** is to release the lock, possibly causing a rescheduling within the
82: ** runtime, then immediately attempting to reacquire the lock and resume.
83: **
84: ** Any other value for timeout will cause the thread to be rescheduled
85: ** either due to explicit notification or an expired interval. The latter
86: ** must be determined by treating time as one part of the monitored data
87: ** being protected by the lock and tested explicitly for an expired
88: ** interval.
89: **
90: ** Returns PR_FAILURE if the caller has not locked the lock associated
91: ** with the condition variable or the thread was interrupted (PR_Interrupt()).
92: ** The particular reason can be extracted with PR_GetError().
93: */
94: NSPR_API(PRStatus) PR_WaitCondVar(PRCondVar *cvar, PRIntervalTime timeout);
95:
96: /*
97: ** Notify ONE thread that is currently waiting on 'cvar'. Which thread is
98: ** dependent on the implementation of the runtime. Common sense would dictate
99: ** that all threads waiting on a single condition have identical semantics,
100: ** therefore which one gets notified is not significant.
101: **
102: ** The calling thead must hold the lock that protects the condition, as
103: ** well as the invariants that are tightly bound to the condition, when
104: ** notify is called.
105: **
106: ** Returns PR_FAILURE if the caller has not locked the lock associated
107: ** with the condition variable.
108: */
109: NSPR_API(PRStatus) PR_NotifyCondVar(PRCondVar *cvar);
110:
111: /*
112: ** Notify all of the threads waiting on the condition variable. The order
113: ** that the threads are notified is indeterminant. The lock that protects
114: ** the condition must be held.
115: **
116: ** Returns PR_FAILURE if the caller has not locked the lock associated
117: ** with the condition variable.
118: */
119: NSPR_API(PRStatus) PR_NotifyAllCondVar(PRCondVar *cvar);
120:
121: PR_END_EXTERN_C
122:
123: #endif /* prcvar_h___ */
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