VirtualBox

source: vbox/trunk/src/VBox/Runtime/common/string/memcmp.cpp@ 34079

Last change on this file since 34079 was 28800, checked in by vboxsync, 15 years ago

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1/* $Id: memcmp.cpp 28800 2010-04-27 08:22:32Z vboxsync $ */
2/** @file
3 * IPRT - CRT Strings, memcmp().
4 */
5
6/*
7 * Copyright (C) 2006-2007 Oracle Corporation
8 *
9 * This file is part of VirtualBox Open Source Edition (OSE), as
10 * available from http://www.virtualbox.org. This file is free software;
11 * you can redistribute it and/or modify it under the terms of the GNU
12 * General Public License (GPL) as published by the Free Software
13 * Foundation, in version 2 as it comes in the "COPYING" file of the
14 * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
15 * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
16 *
17 * The contents of this file may alternatively be used under the terms
18 * of the Common Development and Distribution License Version 1.0
19 * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
20 * VirtualBox OSE distribution, in which case the provisions of the
21 * CDDL are applicable instead of those of the GPL.
22 *
23 * You may elect to license modified versions of this file under the
24 * terms and conditions of either the GPL or the CDDL or both.
25 */
26
27
28/*******************************************************************************
29* Header Files *
30*******************************************************************************/
31#include <iprt/string.h>
32#include <iprt/types.h>
33
34
35/**
36 * Copies a memory.
37 *
38 * @returns 0 if pvDst and pvSrc are equal
39 * @returns <0 if pvDst is 'smaller' than pvSrc.
40 * @returns >0 if pvDst is 'larger' than pvSrc.
41 *
42 * @param pvDst Pointer to the target block.
43 * @param pvSrc Pointer to the source block.
44 * @param cb The size of the block.
45 */
46#ifdef _MSC_VER
47# if _MSC_VER >= 1400
48__checkReturn int __cdecl memcmp(__in_bcount_opt(_Size) const void * pvDst, __in_bcount_opt(_Size) const void * pvSrc, __in size_t cb)
49# else
50int __cdecl memcmp(const void *pvDst, const void *pvSrc, size_t cb)
51# endif
52#else
53int memcmp(const void *pvDst, const void *pvSrc, size_t cb)
54#endif
55{
56 register union
57 {
58 uint8_t const *pu8;
59 uint32_t const *pu32;
60 void const *pv;
61 } uDst, uSrc;
62 uDst.pv = pvDst;
63 uSrc.pv = pvSrc;
64
65 /* 32-bit word compare. */
66 register size_t c = cb >> 2;
67 while (c-- > 0)
68 {
69 /* ASSUMES int is at least 32-bit! */
70 register int32_t iDiff = *uDst.pu32++ - *uSrc.pu32++;
71 if (iDiff)
72 return iDiff;
73 }
74
75 /* Remaining byte moves. */
76 c = cb & 3;
77 while (c-- > 0)
78 {
79 register int8_t iDiff = *uDst.pu8++ - *uSrc.pu8++;
80 if (iDiff)
81 return iDiff;
82 }
83
84 return 0;
85}
86
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