aboutsummaryrefslogtreecommitdiff
path: root/fs/udf/crc.c
blob: f178c63686e0e99aeb2de4babd1c049b32ea0415 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
/*
 * crc.c
 *
 * PURPOSE
 *	Routines to generate, calculate, and test a 16-bit CRC.
 *
 * DESCRIPTION
 *	The CRC code was devised by Don P. Mitchell of AT&T Bell Laboratories
 *	and Ned W. Rhodes of Software Systems Group. It has been published in
 *	"Design and Validation of Computer Protocols", Prentice Hall,
 *	Englewood Cliffs, NJ, 1991, Chapter 3, ISBN 0-13-539925-4.
 *
 *	Copyright is held by AT&T.
 *
 *	AT&T gives permission for the free use of the CRC source code.
 *
 * COPYRIGHT
 *	This file is distributed under the terms of the GNU General Public
 *	License (GPL). Copies of the GPL can be obtained from:
 *		ftp://prep.ai.mit.edu/pub/gnu/GPL
 *	Each contributing author retains all rights to their own work.
 */

#include "udfdecl.h"

static const uint16_t crc_table[256] = {
	0x0000U, 0x1021U, 0x2042U, 0x3063U, 0x4084U, 0x50a5U, 0x60c6U, 0x70e7U,
	0x8108U, 0x9129U, 0xa14aU, 0xb16bU, 0xc18cU, 0xd1adU, 0xe1ceU, 0xf1efU,
	0x1231U, 0x0210U, 0x3273U, 0x2252U, 0x52b5U, 0x4294U, 0x72f7U, 0x62d6U,
	0x9339U, 0x8318U, 0xb37bU, 0xa35aU, 0xd3bdU, 0xc39cU, 0xf3ffU, 0xe3deU,
	0x2462U, 0x3443U, 0x0420U, 0x1401U, 0x64e6U, 0x74c7U, 0x44a4U, 0x5485U,
	0xa56aU, 0xb54bU, 0x8528U, 0x9509U, 0xe5eeU, 0xf5cfU, 0xc5acU, 0xd58dU,
	0x3653U, 0x2672U, 0x1611U, 0x0630U, 0x76d7U, 0x66f6U, 0x5695U, 0x46b4U,
	0xb75bU, 0xa77aU, 0x9719U, 0x8738U, 0xf7dfU, 0xe7feU, 0xd79dU, 0xc7bcU,
	0x48c4U, 0x58e5U, 0x6886U, 0x78a7U, 0x0840U, 0x1861U, 0x2802U, 0x3823U,
	0xc9ccU, 0xd9edU, 0xe98eU, 0xf9afU, 0x8948U, 0x9969U, 0xa90aU, 0xb92bU,
	0x5af5U, 0x4ad4U, 0x7ab7U, 0x6a96U, 0x1a71U, 0x0a50U, 0x3a33U, 0x2a12U,
	0xdbfdU, 0xcbdcU, 0xfbbfU, 0xeb9eU, 0x9b79U, 0x8b58U, 0xbb3bU, 0xab1aU,
	0x6ca6U, 0x7c87U, 0x4ce4U, 0x5cc5U, 0x2c22U, 0x3c03U, 0x0c60U, 0x1c41U,
	0xedaeU, 0xfd8fU, 0xcdecU, 0xddcdU, 0xad2aU, 0xbd0bU, 0x8d68U, 0x9d49U,
	0x7e97U, 0x6eb6U, 0x5ed5U, 0x4ef4U, 0x3e13U, 0x2e32U, 0x1e51U, 0x0e70U,
	0xff9fU, 0xefbeU, 0xdfddU, 0xcffcU, 0xbf1bU, 0xaf3aU, 0x9f59U, 0x8f78U,
	0x9188U, 0x81a9U, 0xb1caU, 0xa1ebU, 0xd10cU, 0xc12dU, 0xf14eU, 0xe16fU,
	0x1080U, 0x00a1U, 0x30c2U, 0x20e3U, 0x5004U, 0x4025U, 0x7046U, 0x6067U,
	0x83b9U, 0x9398U, 0xa3fbU, 0xb3daU, 0xc33dU, 0xd31cU, 0xe37fU, 0xf35eU,
	0x02b1U, 0x1290U, 0x22f3U, 0x32d2U, 0x4235U, 0x5214U, 0x6277U, 0x7256U,
	0xb5eaU, 0xa5cbU, 0x95a8U, 0x8589U, 0xf56eU, 0xe54fU, 0xd52cU, 0xc50dU,
	0x34e2U, 0x24c3U, 0x14a0U, 0x0481U, 0x7466U, 0x6447U, 0x5424U, 0x4405U,
	0xa7dbU, 0xb7faU, 0x8799U, 0x97b8U, 0xe75fU, 0xf77eU, 0xc71dU, 0xd73cU,
	0x26d3U, 0x36f2U, 0x0691U, 0x16b0U, 0x6657U, 0x7676U, 0x4615U, 0x5634U,
	0xd94cU, 0xc96dU, 0xf90eU, 0xe92fU, 0x99c8U, 0x89e9U, 0xb98aU, 0xa9abU,
	0x5844U, 0x4865U, 0x7806U, 0x6827U, 0x18c0U, 0x08e1U, 0x3882U, 0x28a3U,
	0xcb7dU, 0xdb5cU, 0xeb3fU, 0xfb1eU, 0x8bf9U, 0x9bd8U, 0xabbbU, 0xbb9aU,
	0x4a75U, 0x5a54U, 0x6a37U, 0x7a16U, 0x0af1U, 0x1ad0U, 0x2ab3U, 0x3a92U,
	0xfd2eU, 0xed0fU, 0xdd6cU, 0xcd4dU, 0xbdaaU, 0xad8bU, 0x9de8U, 0x8dc9U,
	0x7c26U, 0x6c07U, 0x5c64U, 0x4c45U, 0x3ca2U, 0x2c83U, 0x1ce0U, 0x0cc1U,
	0xef1fU, 0xff3eU, 0xcf5dU, 0xdf7cU, 0xaf9bU, 0xbfbaU, 0x8fd9U, 0x9ff8U,
	0x6e17U, 0x7e36U, 0x4e55U, 0x5e74U, 0x2e93U, 0x3eb2U, 0x0ed1U, 0x1ef0U
};

/*
 * udf_crc
 *
 * PURPOSE
 *	Calculate a 16-bit CRC checksum using ITU-T V.41 polynomial.
 *
 * DESCRIPTION
 *	The OSTA-UDF(tm) 1.50 standard states that using CRCs is mandatory.
 *	The polynomial used is:	x^16 + x^12 + x^15 + 1
 *
 * PRE-CONDITIONS
 *	data		Pointer to the data block.
 *	size		Size of the data block.
 *
 * POST-CONDITIONS
 *	<return>	CRC of the data block.
 *
 * HISTORY
 *	July 21, 1997 - Andrew E. Mileski
 *	Adapted from OSTA-UDF(tm) 1.50 standard.
 */
uint16_t udf_crc(const uint8_t *data, uint32_t size, uint16_t crc)
{
	while (size--)
		crc = crc_table[(crc >> 8 ^ *(data++)) & 0xffU] ^ (crc << 8);

	return crc;
}

/****************************************************************************/
#if defined(TEST)

/*
 * PURPOSE
 *	Test udf_crc()
 *
 * HISTORY
 *	July 21, 1997 - Andrew E. Mileski
 *	Adapted from OSTA-UDF(tm) 1.50 standard.
 */

unsigned char bytes[] = { 0x70U, 0x6AU, 0x77U };

int main(void)
{
	unsigned short x;

	x = udf_crc(bytes, sizeof bytes);
	printf("udf_crc: calculated = %4.4x, correct = %4.4x\n", x, 0x3299U);

	return 0;
}

#endif /* defined(TEST) */

/****************************************************************************/
#if defined(GENERATE)

/*
 * PURPOSE
 *	Generate a table for fast 16-bit CRC calculations (any polynomial).
 *
 * DESCRIPTION
 *	The ITU-T V.41 polynomial is 010041.
 *
 * HISTORY
 *	July 21, 1997 - Andrew E. Mileski
 *	Adapted from OSTA-UDF(tm) 1.50 standard.
 */

#include <stdio.h>

int main(int argc, char **argv)
{
	unsigned long crc, poly;
	int n, i;

	/* Get the polynomial */
	sscanf(argv[1], "%lo", &poly);
	if (poly & 0xffff0000U) {
		fprintf(stderr, "polynomial is too large\en");
		exit(1);
	}

	printf("/* CRC 0%o */\n", poly);

	/* Create a table */
	printf("static unsigned short crc_table[256] = {\n");
	for (n = 0; n < 256; n++) {
		if (n % 8 == 0)
			printf("\t");
		crc = n << 8;
		for (i = 0; i < 8; i++) {
			if (crc & 0x8000U)
				crc = (crc << 1) ^ poly;
			else
				crc <<= 1;
			crc &= 0xFFFFU;
		}
		if (n == 255)
			printf("0x%04xU ", crc);
		else
			printf("0x%04xU, ", crc);
		if (n % 8 == 7)
			printf("\n");
	}
	printf("};\n");

	return 0;
}

#endif /* defined(GENERATE) */