| 1 | /* $Id: adler32.cpp 28800 2010-04-27 08:22:32Z vboxsync $ */
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| 2 | /** @file
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| 3 | * IPRT - Adler-32
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| 4 | */
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| 5 |
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| 6 | /*
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| 7 | * Copyright (C) 2009 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/crc.h>
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| 32 | #include "internal/iprt.h"
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| 33 |
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| 34 | #include <iprt/asm.h>
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| 35 | #include <iprt/assert.h>
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| 36 |
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| 37 |
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| 38 | /*******************************************************************************
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| 39 | * Defined Constants And Macros *
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| 40 | *******************************************************************************/
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| 41 | #define RTCRC_ADLER_32_NUMBER 65521
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| 42 |
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| 43 |
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| 44 | RTDECL(uint32_t) RTCrcAdler32(void const *pv, size_t cb)
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| 45 | {
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| 46 | /* Don't want to do the unrolling twice. */
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| 47 | return RTCrcAdler32Process(RTCrcAdler32Start(), pv, cb);
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| 48 | }
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| 49 |
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| 50 |
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| 51 | RTDECL(uint32_t) RTCrcAdler32Start(void)
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| 52 | {
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| 53 | return 1;
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| 54 | }
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| 55 |
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| 56 |
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| 57 | RTDECL(uint32_t) RTCrcAdler32Process(uint32_t u32Crc, void const *pv, size_t cb)
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| 58 | {
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| 59 | uint8_t const *pbSrc = (uint8_t const *)pv;
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| 60 | uint32_t a = u32Crc & 0xffff;
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| 61 | uint32_t b = u32Crc >> 16;
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| 62 | if (cb < 64 /* randomly selected number */)
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| 63 | {
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| 64 | while (cb-- > 0)
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| 65 | {
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| 66 | a += *pbSrc++;
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| 67 | a %= RTCRC_ADLER_32_NUMBER;
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| 68 | b += a;
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| 69 | b %= RTCRC_ADLER_32_NUMBER;
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| 70 | }
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| 71 | }
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| 72 | else
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| 73 | {
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| 74 | switch (((uintptr_t)pbSrc & 0x3))
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| 75 | {
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| 76 | case 0:
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| 77 | break;
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| 78 |
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| 79 | case 1:
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| 80 | a += *pbSrc++;
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| 81 | a %= RTCRC_ADLER_32_NUMBER;
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| 82 | b += a;
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| 83 | b %= RTCRC_ADLER_32_NUMBER;
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| 84 | cb--;
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| 85 | /* fall thru */
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| 86 |
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| 87 | case 2:
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| 88 | a += *pbSrc++;
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| 89 | a %= RTCRC_ADLER_32_NUMBER;
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| 90 | b += a;
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| 91 | b %= RTCRC_ADLER_32_NUMBER;
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| 92 | cb--;
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| 93 | /* fall thru */
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| 94 |
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| 95 | case 3:
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| 96 | a += *pbSrc++;
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| 97 | a %= RTCRC_ADLER_32_NUMBER;
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| 98 | b += a;
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| 99 | b %= RTCRC_ADLER_32_NUMBER;
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| 100 | cb--;
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| 101 | break;
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| 102 | }
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| 103 |
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| 104 | while (cb >= 4)
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| 105 | {
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| 106 | uint32_t u32 = *(uint32_t const *)pbSrc;
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| 107 | pbSrc += 4;
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| 108 |
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| 109 | a += u32 & 0xff;
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| 110 | a %= RTCRC_ADLER_32_NUMBER;
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| 111 | b += a;
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| 112 | b %= RTCRC_ADLER_32_NUMBER;
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| 113 |
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| 114 | a += (u32 >> 8) & 0xff;
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| 115 | a %= RTCRC_ADLER_32_NUMBER;
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| 116 | b += a;
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| 117 | b %= RTCRC_ADLER_32_NUMBER;
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| 118 |
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| 119 | a += (u32 >> 16) & 0xff;
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| 120 | a %= RTCRC_ADLER_32_NUMBER;
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| 121 | b += a;
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| 122 | b %= RTCRC_ADLER_32_NUMBER;
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| 123 |
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| 124 | a += (u32 >> 24) & 0xff;
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| 125 | a %= RTCRC_ADLER_32_NUMBER;
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| 126 | b += a;
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| 127 | b %= RTCRC_ADLER_32_NUMBER;
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| 128 |
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| 129 | cb -= 4;
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| 130 | }
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| 131 |
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| 132 | switch (cb)
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| 133 | {
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| 134 | case 0:
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| 135 | break;
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| 136 |
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| 137 | case 3:
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| 138 | a += *pbSrc++;
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| 139 | a %= RTCRC_ADLER_32_NUMBER;
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| 140 | b += a;
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| 141 | b %= RTCRC_ADLER_32_NUMBER;
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| 142 | cb--;
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| 143 | /* fall thru */
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| 144 |
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| 145 | case 2:
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| 146 | a += *pbSrc++;
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| 147 | a %= RTCRC_ADLER_32_NUMBER;
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| 148 | b += a;
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| 149 | b %= RTCRC_ADLER_32_NUMBER;
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| 150 | cb--;
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| 151 | /* fall thru */
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| 152 |
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| 153 | case 1:
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| 154 | a += *pbSrc++;
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| 155 | a %= RTCRC_ADLER_32_NUMBER;
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| 156 | b += a;
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| 157 | b %= RTCRC_ADLER_32_NUMBER;
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| 158 | cb--;
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| 159 | break;
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| 160 | }
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| 161 | }
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| 162 |
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| 163 | return a | (b << 16);
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| 164 | }
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| 165 |
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| 166 |
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| 167 | RTDECL(uint32_t) RTCrcAdler32Finish(uint32_t u32Crc)
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| 168 | {
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| 169 | return u32Crc;
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| 170 | }
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| 171 |
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