VirtualBox

source: vbox/trunk/include/iprt/once.h@ 12747

Last change on this file since 12747 was 10940, checked in by vboxsync, 16 years ago

IPRT: Implemented the RTOnce API.

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  • Property svn:keywords set to Author Date Id Revision
File size: 3.1 KB
Line 
1/** @file
2 * IPRT - Execute Once.
3 */
4
5/*
6 * Copyright (C) 2006-2007 Sun Microsystems, Inc.
7 *
8 * This file is part of VirtualBox Open Source Edition (OSE), as
9 * available from http://www.virtualbox.org. This file is free software;
10 * you can redistribute it and/or modify it under the terms of the GNU
11 * General Public License (GPL) as published by the Free Software
12 * Foundation, in version 2 as it comes in the "COPYING" file of the
13 * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
14 * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
15 *
16 * The contents of this file may alternatively be used under the terms
17 * of the Common Development and Distribution License Version 1.0
18 * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
19 * VirtualBox OSE distribution, in which case the provisions of the
20 * CDDL are applicable instead of those of the GPL.
21 *
22 * You may elect to license modified versions of this file under the
23 * terms and conditions of either the GPL or the CDDL or both.
24 *
25 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
26 * Clara, CA 95054 USA or visit http://www.sun.com if you need
27 * additional information or have any questions.
28 */
29
30#ifndef ___iprt_once_h
31#define ___iprt_once_h
32
33#include <iprt/cdefs.h>
34#include <iprt/types.h>
35#include <iprt/err.h>
36
37__BEGIN_DECLS
38
39/** @defgroup grp_rt_once RTOnce - Execute Once
40 * @ingroup grp_rt
41 * @{
42 */
43
44/**
45 * Execute once structure.
46 *
47 * This is typically a global variable that is statically initialized
48 * by RTONCE_INITIALIZER.
49 */
50typedef struct RTONCE
51{
52 /** Event semaphore that the other guys are blocking on. */
53 RTSEMEVENTMULTI volatile hEventMulti;
54 /** Reference counter for hEventMulti. */
55 int32_t volatile cEventRefs;
56 /** -1 when uninitialized, 1 when initializing (busy) and 2 when done. */
57 int32_t volatile iState;
58 /** The return code of pfnOnce. */
59 int32_t volatile rc;
60} RTONCE;
61/** Pointer to a execute once struct. */
62typedef RTONCE *PRTONCE;
63
64/** Static initializer for RTONCE variables. */
65#define RTONCE_INITIALIZER { NIL_RTSEMEVENTMULTI, 0, -1, VERR_INTERNAL_ERROR }
66
67
68/**
69 * Callback that gets executed once.
70 *
71 * @returns IPRT style status code, RTOnce returns this.
72 *
73 * @param pvUser1 The first user parameter.
74 * @param pvUser2 The second user parameter.
75 */
76typedef DECLCALLBACK(int32_t) FNRTONCE(void *pvUser1, void *pvUser2);
77/** Pointer to a FNRTONCE. */
78typedef FNRTONCE *PFNRTONCE;
79
80/**
81 * Serializes execution of the pfnOnce function, making sure it's
82 * executed exactly once and that nobody returns from RTOnce before
83 * it has executed successfully.
84 *
85 * @returns IPRT like status code returned by pfnOnce.
86 *
87 * @param pOnce Pointer to the execute once variable.
88 * @param pfnOnce The function to executed once.
89 * @param pvUser1 The first user parameter for pfnOnce.
90 * @param pvUser2 The second user parameter for pfnOnce.
91 */
92RTDECL(int) RTOnce(PRTONCE pOnce, PFNRTONCE pfnOnce, void *pvUser1, void *pvUser2);
93
94/** @} */
95
96__END_DECLS
97
98#endif
99
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