VirtualBox

source: vbox/trunk/src/VBox/Runtime/common/checksum/adler32.cpp@ 81106

Last change on this file since 81106 was 76553, checked in by vboxsync, 6 years ago

scm --update-copyright-year

  • Property svn:eol-style set to native
  • Property svn:keywords set to Author Date Id Revision
File size: 4.8 KB
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1/* $Id: adler32.cpp 76553 2019-01-01 01:45:53Z vboxsync $ */
2/** @file
3 * IPRT - Adler-32
4 */
5
6/*
7 * Copyright (C) 2009-2019 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/crc.h>
32#include "internal/iprt.h"
33
34#include <iprt/asm.h>
35#include <iprt/assert.h>
36
37
38/*********************************************************************************************************************************
39* Defined Constants And Macros *
40*********************************************************************************************************************************/
41#define RTCRC_ADLER_32_NUMBER 65521
42
43
44RTDECL(uint32_t) RTCrcAdler32(void const *pv, size_t cb)
45{
46 /* Don't want to do the unrolling twice. */
47 return RTCrcAdler32Process(RTCrcAdler32Start(), pv, cb);
48}
49
50
51RTDECL(uint32_t) RTCrcAdler32Start(void)
52{
53 return 1;
54}
55
56
57RTDECL(uint32_t) RTCrcAdler32Process(uint32_t u32Crc, void const *pv, size_t cb)
58{
59 uint8_t const *pbSrc = (uint8_t const *)pv;
60 uint32_t a = u32Crc & 0xffff;
61 uint32_t b = u32Crc >> 16;
62 if (cb < 64 /* randomly selected number */)
63 {
64 while (cb-- > 0)
65 {
66 a += *pbSrc++;
67 a %= RTCRC_ADLER_32_NUMBER;
68 b += a;
69 b %= RTCRC_ADLER_32_NUMBER;
70 }
71 }
72 else
73 {
74 switch (((uintptr_t)pbSrc & 0x3))
75 {
76 case 0:
77 break;
78
79 case 1:
80 a += *pbSrc++;
81 a %= RTCRC_ADLER_32_NUMBER;
82 b += a;
83 b %= RTCRC_ADLER_32_NUMBER;
84 cb--;
85 RT_FALL_THRU();
86
87 case 2:
88 a += *pbSrc++;
89 a %= RTCRC_ADLER_32_NUMBER;
90 b += a;
91 b %= RTCRC_ADLER_32_NUMBER;
92 cb--;
93 RT_FALL_THRU();
94
95 case 3:
96 a += *pbSrc++;
97 a %= RTCRC_ADLER_32_NUMBER;
98 b += a;
99 b %= RTCRC_ADLER_32_NUMBER;
100 cb--;
101 break;
102 }
103
104 while (cb >= 4)
105 {
106 uint32_t u32 = *(uint32_t const *)pbSrc;
107 pbSrc += 4;
108
109 a += u32 & 0xff;
110 a %= RTCRC_ADLER_32_NUMBER;
111 b += a;
112 b %= RTCRC_ADLER_32_NUMBER;
113
114 a += (u32 >> 8) & 0xff;
115 a %= RTCRC_ADLER_32_NUMBER;
116 b += a;
117 b %= RTCRC_ADLER_32_NUMBER;
118
119 a += (u32 >> 16) & 0xff;
120 a %= RTCRC_ADLER_32_NUMBER;
121 b += a;
122 b %= RTCRC_ADLER_32_NUMBER;
123
124 a += (u32 >> 24) & 0xff;
125 a %= RTCRC_ADLER_32_NUMBER;
126 b += a;
127 b %= RTCRC_ADLER_32_NUMBER;
128
129 cb -= 4;
130 }
131
132 switch (cb)
133 {
134 case 0:
135 break;
136
137 case 3:
138 a += *pbSrc++;
139 a %= RTCRC_ADLER_32_NUMBER;
140 b += a;
141 b %= RTCRC_ADLER_32_NUMBER;
142 cb--;
143 RT_FALL_THRU();
144
145 case 2:
146 a += *pbSrc++;
147 a %= RTCRC_ADLER_32_NUMBER;
148 b += a;
149 b %= RTCRC_ADLER_32_NUMBER;
150 cb--;
151 RT_FALL_THRU();
152
153 case 1:
154 a += *pbSrc++;
155 a %= RTCRC_ADLER_32_NUMBER;
156 b += a;
157 b %= RTCRC_ADLER_32_NUMBER;
158 cb--;
159 break;
160 }
161 }
162
163 return a | (b << 16);
164}
165
166
167RTDECL(uint32_t) RTCrcAdler32Finish(uint32_t u32Crc)
168{
169 return u32Crc;
170}
171
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