1 /* @(#)crc16.c 1.9 09/07/05 Copyright 1998-2009 J. Schilling */
2 #include <schily/mconfig.h>
3 #ifndef lint
4 static UConst char sccsid[] =
5 "@(#)crc16.c 1.9 09/07/05 Copyright 1998-2009 J. Schilling";
6 #endif
7 /*
8 * Q-subchannel CRC subroutines
9 *
10 * Polynom is: p(x) = x ** 16 + x ** 12 + x ** 5 + 1
11 * If computed over 12 bytes, the result must be zero.
12 * On the disk the CRC bits are inverted.
13 *
14 * Copyright (c) 1998-2009 J. Schilling
15 */
16 /*
17 * The contents of this file are subject to the terms of the
18 * Common Development and Distribution License, Version 1.0 only
19 * (the "License"). You may not use this file except in compliance
20 * with the License.
21 *
22 * See the file CDDL.Schily.txt in this distribution for details.
23 * A copy of the CDDL is also available via the Internet at
24 * http://www.opensource.org/licenses/cddl1.txt
25 *
26 * When distributing Covered Code, include this CDDL HEADER in each
27 * file and include the License file CDDL.Schily.txt from this distribution.
28 */
29
30 #include <schily/mconfig.h>
31 #include <schily/standard.h>
32 #include <schily/utypes.h>
33 #include "crc16.h"
34
35 LOCAL UInt16_t updcrc __PR((Uint p_crc, UInt8_t *cp, Uint cnt));
36 /*LOCAL UInt16_t calcCRC __PR((Uchar *buf, Uint bsize));*/
37 EXPORT UInt16_t calcCRC __PR((Uchar *buf, Uint bsize));
38 EXPORT UInt16_t fillcrc __PR((Uchar *buf, Uint bsize));
39 EXPORT UInt16_t flip_crc_error_corr __PR((Uchar *b, Uint bsize, Uint p_crc));
40
41
42 /* number of bits in CRC: don't change it. */
43 #define BPW 16
44
45 /* this the number of bits per char: don't change it. */
46 #define BPB 8
47
48 LOCAL UInt16_t crctab[1<<BPB] = {
49 0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7,
50 0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef,
51 0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6,
52 0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de,
53 0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485,
54 0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d,
55 0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4,
56 0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc,
57 0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823,
58 0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b,
59 0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12,
60 0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a,
61 0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41,
62 0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49,
63 0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70,
64 0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78,
65 0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f,
66 0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067,
67 0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e,
68 0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256,
69 0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d,
70 0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
71 0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c,
72 0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634,
73 0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab,
74 0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3,
75 0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a,
76 0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92,
77 0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9,
78 0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1,
79 0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8,
80 0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0,
81 };
82
83 #define SUBSIZE 96 /* 12 bytes with 8 bits */
84
85 LOCAL UInt16_t
updcrc(p_crc,cp,cnt)86 updcrc(p_crc, cp, cnt)
87 Uint p_crc;
88 register UInt8_t *cp;
89 register Uint cnt;
90 {
91 register UInt16_t crc = p_crc;
92
93 while (cnt-- > 0) {
94 crc = (crc<<BPB) ^ crctab[(crc>>(BPW-BPB)) ^ (*cp++)];
95 }
96 return (crc);
97 }
98
99 /*LOCAL UInt16_t*/
100 EXPORT UInt16_t
calcCRC(buf,bsize)101 calcCRC(buf, bsize)
102 Uchar *buf;
103 Uint bsize;
104 {
105 return (updcrc(0x0000, (UInt8_t *)buf, bsize));
106 }
107
108 /*
109 * CRC f�r Q-Sub f�llen
110 */
111 EXPORT UInt16_t
fillcrc(buf,bsize)112 fillcrc(buf, bsize)
113 Uchar *buf;
114 Uint bsize;
115 {
116 UInt16_t crc = calcCRC(buf, bsize-2);
117
118 /*
119 * Invert CRC bits for RED Book compliance.
120 */
121 crc = crc ^ 0xFFFF;
122
123 buf[bsize-2] = (crc >> 8) & 0xFF;
124 buf[bsize-1] = crc & 0xFF;
125 return (crc);
126 }
127
128 LOCAL UInt8_t fliptab[BPB] = {
129 0x01,
130 0x02,
131 0x04,
132 0x08,
133 0x10,
134 0x20,
135 0x40,
136 0x80,
137 };
138
139 EXPORT UInt16_t
flip_crc_error_corr(b,bsize,p_crc)140 flip_crc_error_corr(b, bsize, p_crc)
141 Uchar *b;
142 Uint bsize;
143 Uint p_crc;
144 {
145 register UInt16_t crc = p_crc;
146 register Uint btsize = bsize * BPB;
147
148 if (crc != 0) {
149 int i;
150
151 for (i = 0; i < btsize; i++) {
152 UInt8_t c;
153
154 c = fliptab[i % BPB];
155 b[i / BPB] ^= c;
156 if ((crc = calcCRC(b, bsize)) == 0) {
157 return (crc);
158 }
159 b[i / BPB] ^= c;
160 }
161 }
162 return (crc & 0xffff);
163 }
164