| 1 | /* $Id: memcmp.cpp 57358 2015-08-14 15:16:38Z vboxsync $ */
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| 2 | /** @file
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| 3 | * IPRT - CRT Strings, memcmp().
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| 4 | */
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| 5 |
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| 6 | /*
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| 7 | * Copyright (C) 2006-2015 Oracle Corporation
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| 8 | *
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| 9 | * This file is part of VirtualBox Open Source Edition (OSE), as
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| 10 | * available from http://www.virtualbox.org. This file is free software;
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| 11 | * you can redistribute it and/or modify it under the terms of the GNU
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| 12 | * General Public License (GPL) as published by the Free Software
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| 13 | * Foundation, in version 2 as it comes in the "COPYING" file of the
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| 14 | * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
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| 15 | * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
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| 16 | *
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| 17 | * The contents of this file may alternatively be used under the terms
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| 18 | * of the Common Development and Distribution License Version 1.0
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| 19 | * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
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| 20 | * VirtualBox OSE distribution, in which case the provisions of the
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| 21 | * CDDL are applicable instead of those of the GPL.
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| 22 | *
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| 23 | * You may elect to license modified versions of this file under the
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| 24 | * terms and conditions of either the GPL or the CDDL or both.
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| 25 | */
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| 26 |
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| 27 |
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| 28 | /*********************************************************************************************************************************
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| 29 | * Header Files *
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| 30 | *********************************************************************************************************************************/
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| 31 | #include <iprt/string.h>
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| 32 | #include <iprt/types.h>
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| 33 |
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| 34 |
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| 35 | /**
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| 36 | * Copies a memory.
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| 37 | *
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| 38 | * @returns 0 if pvDst and pvSrc are equal
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| 39 | * @returns <0 if pvDst is 'smaller' than pvSrc.
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| 40 | * @returns >0 if pvDst is 'larger' than pvSrc.
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| 41 | *
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| 42 | * @param pvDst Pointer to the target block.
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| 43 | * @param pvSrc Pointer to the source block.
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| 44 | * @param cb The size of the block.
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| 45 | */
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| 46 | #ifdef _MSC_VER
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| 47 | # if _MSC_VER >= 1400
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| 48 | __checkReturn int __cdecl memcmp(__in_bcount_opt(_Size) const void * pvDst, __in_bcount_opt(_Size) const void * pvSrc, __in size_t cb)
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| 49 | # else
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| 50 | int __cdecl memcmp(const void *pvDst, const void *pvSrc, size_t cb)
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| 51 | # endif
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| 52 | #else
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| 53 | int memcmp(const void *pvDst, const void *pvSrc, size_t cb)
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| 54 | #endif
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| 55 | {
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| 56 | register union
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| 57 | {
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| 58 | uint8_t const *pu8;
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| 59 | uint32_t const *pu32;
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| 60 | void const *pv;
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| 61 | } uDst, uSrc;
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| 62 | uDst.pv = pvDst;
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| 63 | uSrc.pv = pvSrc;
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| 64 |
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| 65 | /* 32-bit word compare. */
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| 66 | register size_t c = cb >> 2;
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| 67 | while (c-- > 0)
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| 68 | {
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| 69 | /* ASSUMES int is at least 32-bit! */
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| 70 | register int32_t iDiff = *uDst.pu32++ - *uSrc.pu32++;
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| 71 | if (iDiff)
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| 72 | return iDiff;
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| 73 | }
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| 74 |
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| 75 | /* Remaining byte moves. */
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| 76 | c = cb & 3;
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| 77 | while (c-- > 0)
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| 78 | {
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| 79 | register int8_t iDiff = *uDst.pu8++ - *uSrc.pu8++;
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| 80 | if (iDiff)
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| 81 | return iDiff;
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| 82 | }
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| 83 |
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| 84 | return 0;
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| 85 | }
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| 86 |
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