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) 1999-2000 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/*
36 * File: pripcsem.h
37 *
38 * Description: named semaphores for interprocess
39 * synchronization
40 *
41 * Unrelated processes obtain access to a shared semaphore
42 * by specifying its name.
43 *
44 * Our goal is to support named semaphores on at least
45 * Unix and Win32 platforms.  The implementation will use
46 * one of the three native semaphore APIs: POSIX, System V,
47 * and Win32.
48 *
49 * Because POSIX named semaphores have kernel persistence,
50 * we are forced to have a delete function in this API.
51 */
52
53#ifndef pripcsem_h___
54#define pripcsem_h___
55
56#include "prtypes.h"
57#include "prio.h"
58
59PR_BEGIN_EXTERN_C
60
61/*
62 * PRSem is an opaque structure that represents a named
63 * semaphore.
64 */
65typedef struct PRSem PRSem;
66
67/*
68 * PR_OpenSemaphore --
69 *
70 * Create or open a named semaphore with the specified name.
71 * A handle to the semaphore is returned.
72 *
73 * If the named semaphore doesn't exist and the PR_SEM_CREATE
74 * flag is specified, the named semaphore is created.  The
75 * created semaphore needs to be removed from the system with
76 * a PR_DeleteSemaphore call.
77 *
78 * If PR_SEM_CREATE is specified, the third argument is the
79 * access permission bits of the new semaphore (same
80 * interpretation as the mode argument to PR_Open) and the
81 * fourth argument is the initial value of the new semaphore.
82 * If PR_SEM_CREATE is not specified, the third and fourth
83 * arguments are ignored.
84 */
85
86#define PR_SEM_CREATE 0x1  /* create if not exist */
87#define PR_SEM_EXCL   0x2  /* fail if already exists */
88
89NSPR_API(PRSem *) PR_OpenSemaphore(
90    const char *name, PRIntn flags, PRIntn mode, PRUintn value);
91
92/*
93 * PR_WaitSemaphore --
94 *
95 * If the value of the semaphore is > 0, decrement the value and return.
96 * If the value is 0, sleep until the value becomes > 0, then decrement
97 * the value and return.
98 *
99 * The "test and decrement" operation is performed atomically.
100 */
101
102NSPR_API(PRStatus) PR_WaitSemaphore(PRSem *sem);
103
104/*
105 * PR_PostSemaphore --
106 *
107 * Increment the value of the named semaphore by 1.
108 */
109
110NSPR_API(PRStatus) PR_PostSemaphore(PRSem *sem);
111
112/*
113 * PR_CloseSemaphore --
114 *
115 * Close a named semaphore handle.
116 */
117
118NSPR_API(PRStatus) PR_CloseSemaphore(PRSem *sem);
119
120/*
121 * PR_DeleteSemaphore --
122 *
123 * Remove a named semaphore from the system.
124 */
125
126NSPR_API(PRStatus) PR_DeleteSemaphore(const char *name);
127
128PR_END_EXTERN_C
129
130#endif /* pripcsem_h___ */
131