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 prsem_h___
36#define prsem_h___
37
38/*
39** API for counting semaphores. Semaphores are counting synchronizing
40** variables based on a lock and a condition variable.  They are lightweight
41** contention control for a given count of resources.
42*/
43#include "prtypes.h"
44
45PR_BEGIN_EXTERN_C
46
47typedef struct PRSemaphore PRSemaphore;
48
49/*
50** Create a new semaphore object.
51*/
52NSPR_API(PRSemaphore*) PR_NewSem(PRUintn value);
53
54/*
55** Destroy the given semaphore object.
56**
57*/
58NSPR_API(void) PR_DestroySem(PRSemaphore *sem);
59
60/*
61** Wait on a Semaphore.
62**
63** This routine allows a calling thread to wait or proceed depending upon the
64** state of the semahore sem. The thread can proceed only if the counter value
65** of the semaphore sem is currently greater than 0. If the value of semaphore
66** sem is positive, it is decremented by one and the routine returns immediately
67** allowing the calling thread to continue. If the value of semaphore sem is 0,
68** the calling thread blocks awaiting the semaphore to be released by another
69** thread.
70**
71** This routine can return PR_PENDING_INTERRUPT if the waiting thread
72** has been interrupted.
73*/
74NSPR_API(PRStatus) PR_WaitSem(PRSemaphore *sem);
75
76/*
77** This routine increments the counter value of the semaphore. If other threads
78** are blocked for the semaphore, then the scheduler will determine which ONE
79** thread will be unblocked.
80*/
81NSPR_API(void) PR_PostSem(PRSemaphore *sem);
82
83/*
84** Returns the value of the semaphore referenced by sem without affecting
85** the state of the semaphore.  The value represents the semaphore vaule
86F** at the time of the call, but may not be the actual value when the
87** caller inspects it.
88*/
89NSPR_API(PRUintn) PR_GetValueSem(PRSemaphore *sem);
90
91PR_END_EXTERN_C
92
93#endif /* prsem_h___ */
94