diff options
author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 18:20:36 -0400 |
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committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 18:20:36 -0400 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /fs/udf/crc.c |
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'fs/udf/crc.c')
-rw-r--r-- | fs/udf/crc.c | 178 |
1 files changed, 178 insertions, 0 deletions
diff --git a/fs/udf/crc.c b/fs/udf/crc.c new file mode 100644 index 000000000000..d95c6e38a455 --- /dev/null +++ b/fs/udf/crc.c | |||
@@ -0,0 +1,178 @@ | |||
1 | /* | ||
2 | * crc.c | ||
3 | * | ||
4 | * PURPOSE | ||
5 | * Routines to generate, calculate, and test a 16-bit CRC. | ||
6 | * | ||
7 | * DESCRIPTION | ||
8 | * The CRC code was devised by Don P. Mitchell of AT&T Bell Laboratories | ||
9 | * and Ned W. Rhodes of Software Systems Group. It has been published in | ||
10 | * "Design and Validation of Computer Protocols", Prentice Hall, | ||
11 | * Englewood Cliffs, NJ, 1991, Chapter 3, ISBN 0-13-539925-4. | ||
12 | * | ||
13 | * Copyright is held by AT&T. | ||
14 | * | ||
15 | * AT&T gives permission for the free use of the CRC source code. | ||
16 | * | ||
17 | * CONTACTS | ||
18 | * E-mail regarding any portion of the Linux UDF file system should be | ||
19 | * directed to the development team mailing list (run by majordomo): | ||
20 | * linux_udf@hpesjro.fc.hp.com | ||
21 | * | ||
22 | * COPYRIGHT | ||
23 | * This file is distributed under the terms of the GNU General Public | ||
24 | * License (GPL). Copies of the GPL can be obtained from: | ||
25 | * ftp://prep.ai.mit.edu/pub/gnu/GPL | ||
26 | * Each contributing author retains all rights to their own work. | ||
27 | */ | ||
28 | |||
29 | #include "udfdecl.h" | ||
30 | |||
31 | static uint16_t crc_table[256] = { | ||
32 | 0x0000U, 0x1021U, 0x2042U, 0x3063U, 0x4084U, 0x50a5U, 0x60c6U, 0x70e7U, | ||
33 | 0x8108U, 0x9129U, 0xa14aU, 0xb16bU, 0xc18cU, 0xd1adU, 0xe1ceU, 0xf1efU, | ||
34 | 0x1231U, 0x0210U, 0x3273U, 0x2252U, 0x52b5U, 0x4294U, 0x72f7U, 0x62d6U, | ||
35 | 0x9339U, 0x8318U, 0xb37bU, 0xa35aU, 0xd3bdU, 0xc39cU, 0xf3ffU, 0xe3deU, | ||
36 | 0x2462U, 0x3443U, 0x0420U, 0x1401U, 0x64e6U, 0x74c7U, 0x44a4U, 0x5485U, | ||
37 | 0xa56aU, 0xb54bU, 0x8528U, 0x9509U, 0xe5eeU, 0xf5cfU, 0xc5acU, 0xd58dU, | ||
38 | 0x3653U, 0x2672U, 0x1611U, 0x0630U, 0x76d7U, 0x66f6U, 0x5695U, 0x46b4U, | ||
39 | 0xb75bU, 0xa77aU, 0x9719U, 0x8738U, 0xf7dfU, 0xe7feU, 0xd79dU, 0xc7bcU, | ||
40 | 0x48c4U, 0x58e5U, 0x6886U, 0x78a7U, 0x0840U, 0x1861U, 0x2802U, 0x3823U, | ||
41 | 0xc9ccU, 0xd9edU, 0xe98eU, 0xf9afU, 0x8948U, 0x9969U, 0xa90aU, 0xb92bU, | ||
42 | 0x5af5U, 0x4ad4U, 0x7ab7U, 0x6a96U, 0x1a71U, 0x0a50U, 0x3a33U, 0x2a12U, | ||
43 | 0xdbfdU, 0xcbdcU, 0xfbbfU, 0xeb9eU, 0x9b79U, 0x8b58U, 0xbb3bU, 0xab1aU, | ||
44 | 0x6ca6U, 0x7c87U, 0x4ce4U, 0x5cc5U, 0x2c22U, 0x3c03U, 0x0c60U, 0x1c41U, | ||
45 | 0xedaeU, 0xfd8fU, 0xcdecU, 0xddcdU, 0xad2aU, 0xbd0bU, 0x8d68U, 0x9d49U, | ||
46 | 0x7e97U, 0x6eb6U, 0x5ed5U, 0x4ef4U, 0x3e13U, 0x2e32U, 0x1e51U, 0x0e70U, | ||
47 | 0xff9fU, 0xefbeU, 0xdfddU, 0xcffcU, 0xbf1bU, 0xaf3aU, 0x9f59U, 0x8f78U, | ||
48 | 0x9188U, 0x81a9U, 0xb1caU, 0xa1ebU, 0xd10cU, 0xc12dU, 0xf14eU, 0xe16fU, | ||
49 | 0x1080U, 0x00a1U, 0x30c2U, 0x20e3U, 0x5004U, 0x4025U, 0x7046U, 0x6067U, | ||
50 | 0x83b9U, 0x9398U, 0xa3fbU, 0xb3daU, 0xc33dU, 0xd31cU, 0xe37fU, 0xf35eU, | ||
51 | 0x02b1U, 0x1290U, 0x22f3U, 0x32d2U, 0x4235U, 0x5214U, 0x6277U, 0x7256U, | ||
52 | 0xb5eaU, 0xa5cbU, 0x95a8U, 0x8589U, 0xf56eU, 0xe54fU, 0xd52cU, 0xc50dU, | ||
53 | 0x34e2U, 0x24c3U, 0x14a0U, 0x0481U, 0x7466U, 0x6447U, 0x5424U, 0x4405U, | ||
54 | 0xa7dbU, 0xb7faU, 0x8799U, 0x97b8U, 0xe75fU, 0xf77eU, 0xc71dU, 0xd73cU, | ||
55 | 0x26d3U, 0x36f2U, 0x0691U, 0x16b0U, 0x6657U, 0x7676U, 0x4615U, 0x5634U, | ||
56 | 0xd94cU, 0xc96dU, 0xf90eU, 0xe92fU, 0x99c8U, 0x89e9U, 0xb98aU, 0xa9abU, | ||
57 | 0x5844U, 0x4865U, 0x7806U, 0x6827U, 0x18c0U, 0x08e1U, 0x3882U, 0x28a3U, | ||
58 | 0xcb7dU, 0xdb5cU, 0xeb3fU, 0xfb1eU, 0x8bf9U, 0x9bd8U, 0xabbbU, 0xbb9aU, | ||
59 | 0x4a75U, 0x5a54U, 0x6a37U, 0x7a16U, 0x0af1U, 0x1ad0U, 0x2ab3U, 0x3a92U, | ||
60 | 0xfd2eU, 0xed0fU, 0xdd6cU, 0xcd4dU, 0xbdaaU, 0xad8bU, 0x9de8U, 0x8dc9U, | ||
61 | 0x7c26U, 0x6c07U, 0x5c64U, 0x4c45U, 0x3ca2U, 0x2c83U, 0x1ce0U, 0x0cc1U, | ||
62 | 0xef1fU, 0xff3eU, 0xcf5dU, 0xdf7cU, 0xaf9bU, 0xbfbaU, 0x8fd9U, 0x9ff8U, | ||
63 | 0x6e17U, 0x7e36U, 0x4e55U, 0x5e74U, 0x2e93U, 0x3eb2U, 0x0ed1U, 0x1ef0U | ||
64 | }; | ||
65 | |||
66 | /* | ||
67 | * udf_crc | ||
68 | * | ||
69 | * PURPOSE | ||
70 | * Calculate a 16-bit CRC checksum using ITU-T V.41 polynomial. | ||
71 | * | ||
72 | * DESCRIPTION | ||
73 | * The OSTA-UDF(tm) 1.50 standard states that using CRCs is mandatory. | ||
74 | * The polynomial used is: x^16 + x^12 + x^15 + 1 | ||
75 | * | ||
76 | * PRE-CONDITIONS | ||
77 | * data Pointer to the data block. | ||
78 | * size Size of the data block. | ||
79 | * | ||
80 | * POST-CONDITIONS | ||
81 | * <return> CRC of the data block. | ||
82 | * | ||
83 | * HISTORY | ||
84 | * July 21, 1997 - Andrew E. Mileski | ||
85 | * Adapted from OSTA-UDF(tm) 1.50 standard. | ||
86 | */ | ||
87 | uint16_t | ||
88 | udf_crc(uint8_t *data, uint32_t size, uint16_t crc) | ||
89 | { | ||
90 | while (size--) | ||
91 | crc = crc_table[(crc >> 8 ^ *(data++)) & 0xffU] ^ (crc << 8); | ||
92 | |||
93 | return crc; | ||
94 | } | ||
95 | |||
96 | /****************************************************************************/ | ||
97 | #if defined(TEST) | ||
98 | |||
99 | /* | ||
100 | * PURPOSE | ||
101 | * Test udf_crc() | ||
102 | * | ||
103 | * HISTORY | ||
104 | * July 21, 1997 - Andrew E. Mileski | ||
105 | * Adapted from OSTA-UDF(tm) 1.50 standard. | ||
106 | */ | ||
107 | |||
108 | unsigned char bytes[] = { 0x70U, 0x6AU, 0x77U }; | ||
109 | |||
110 | int main(void) | ||
111 | { | ||
112 | unsigned short x; | ||
113 | |||
114 | x = udf_crc16(bytes, sizeof bytes); | ||
115 | printf("udf_crc16: calculated = %4.4x, correct = %4.4x\n", x, 0x3299U); | ||
116 | |||
117 | return 0; | ||
118 | } | ||
119 | |||
120 | #endif /* defined(TEST) */ | ||
121 | |||
122 | /****************************************************************************/ | ||
123 | #if defined(GENERATE) | ||
124 | |||
125 | /* | ||
126 | * PURPOSE | ||
127 | * Generate a table for fast 16-bit CRC calculations (any polynomial). | ||
128 | * | ||
129 | * DESCRIPTION | ||
130 | * The ITU-T V.41 polynomial is 010041. | ||
131 | * | ||
132 | * HISTORY | ||
133 | * July 21, 1997 - Andrew E. Mileski | ||
134 | * Adapted from OSTA-UDF(tm) 1.50 standard. | ||
135 | */ | ||
136 | |||
137 | #include <stdio.h> | ||
138 | |||
139 | int main(int argc, char **argv) | ||
140 | { | ||
141 | unsigned long crc, poly; | ||
142 | int n, i; | ||
143 | |||
144 | /* Get the polynomial */ | ||
145 | sscanf(argv[1], "%lo", &poly); | ||
146 | if (poly & 0xffff0000U){ | ||
147 | fprintf(stderr, "polynomial is too large\en"); | ||
148 | exit(1); | ||
149 | } | ||
150 | |||
151 | printf("/* CRC 0%o */\n", poly); | ||
152 | |||
153 | /* Create a table */ | ||
154 | printf("static unsigned short crc_table[256] = {\n"); | ||
155 | for (n = 0; n < 256; n++){ | ||
156 | if (n % 8 == 0) | ||
157 | printf("\t"); | ||
158 | crc = n << 8; | ||
159 | for (i = 0; i < 8; i++){ | ||
160 | if(crc & 0x8000U) | ||
161 | crc = (crc << 1) ^ poly; | ||
162 | else | ||
163 | crc <<= 1; | ||
164 | crc &= 0xFFFFU; | ||
165 | } | ||
166 | if (n == 255) | ||
167 | printf("0x%04xU ", crc); | ||
168 | else | ||
169 | printf("0x%04xU, ", crc); | ||
170 | if(n % 8 == 7) | ||
171 | printf("\n"); | ||
172 | } | ||
173 | printf("};\n"); | ||
174 | |||
175 | return 0; | ||
176 | } | ||
177 | |||
178 | #endif /* defined(GENERATE) */ | ||