Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Oct 15, 2000 Matt Domsch <Matt_Domsch@dell.com> |
| 3 | * Nicer crc32 functions/docs submitted by linux@horizon.com. Thanks! |
| 4 | * Code was from the public domain, copyright abandoned. Code was |
| 5 | * subsequently included in the kernel, thus was re-licensed under the |
| 6 | * GNU GPL v2. |
| 7 | * |
| 8 | * Oct 12, 2000 Matt Domsch <Matt_Domsch@dell.com> |
| 9 | * Same crc32 function was used in 5 other places in the kernel. |
| 10 | * I made one version, and deleted the others. |
| 11 | * There are various incantations of crc32(). Some use a seed of 0 or ~0. |
| 12 | * Some xor at the end with ~0. The generic crc32() function takes |
| 13 | * seed as an argument, and doesn't xor at the end. Then individual |
| 14 | * users can do whatever they need. |
| 15 | * drivers/net/smc9194.c uses seed ~0, doesn't xor with ~0. |
| 16 | * fs/jffs2 uses seed 0, doesn't xor with ~0. |
| 17 | * fs/partitions/efi.c uses seed ~0, xor's with ~0. |
| 18 | * |
| 19 | * This source code is licensed under the GNU General Public License, |
| 20 | * Version 2. See the file COPYING for more details. |
| 21 | */ |
| 22 | |
| 23 | #include <linux/crc32.h> |
| 24 | #include <linux/kernel.h> |
| 25 | #include <linux/module.h> |
| 26 | #include <linux/compiler.h> |
| 27 | #include <linux/types.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 28 | #include <linux/init.h> |
| 29 | #include <asm/atomic.h> |
| 30 | #include "crc32defs.h" |
| 31 | #if CRC_LE_BITS == 8 |
Joakim Tjernlund | 4f2a946 | 2010-03-05 13:43:55 -0800 | [diff] [blame] | 32 | # define tole(x) __constant_cpu_to_le32(x) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 33 | #else |
Joakim Tjernlund | 4f2a946 | 2010-03-05 13:43:55 -0800 | [diff] [blame] | 34 | # define tole(x) (x) |
| 35 | #endif |
| 36 | |
| 37 | #if CRC_BE_BITS == 8 |
| 38 | # define tobe(x) __constant_cpu_to_be32(x) |
| 39 | #else |
| 40 | # define tobe(x) (x) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 41 | #endif |
| 42 | #include "crc32table.h" |
| 43 | |
| 44 | MODULE_AUTHOR("Matt Domsch <Matt_Domsch@dell.com>"); |
| 45 | MODULE_DESCRIPTION("Ethernet CRC32 calculations"); |
| 46 | MODULE_LICENSE("GPL"); |
| 47 | |
Joakim Tjernlund | ddcaccb | 2009-12-14 18:01:33 -0800 | [diff] [blame] | 48 | #if CRC_LE_BITS == 8 || CRC_BE_BITS == 8 |
| 49 | |
| 50 | static inline u32 |
Joakim Tjernlund | 836e2af | 2010-05-24 14:33:31 -0700 | [diff] [blame^] | 51 | crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256]) |
Joakim Tjernlund | ddcaccb | 2009-12-14 18:01:33 -0800 | [diff] [blame] | 52 | { |
| 53 | # ifdef __LITTLE_ENDIAN |
Joakim Tjernlund | 836e2af | 2010-05-24 14:33:31 -0700 | [diff] [blame^] | 54 | # define DO_CRC(x) crc = tab[0][(crc ^ (x)) & 255] ^ (crc >> 8) |
| 55 | # define DO_CRC4 crc = tab[3][(crc) & 255] ^ \ |
| 56 | tab[2][(crc >> 8) & 255] ^ \ |
| 57 | tab[1][(crc >> 16) & 255] ^ \ |
| 58 | tab[0][(crc >> 24) & 255] |
Joakim Tjernlund | ddcaccb | 2009-12-14 18:01:33 -0800 | [diff] [blame] | 59 | # else |
Joakim Tjernlund | 836e2af | 2010-05-24 14:33:31 -0700 | [diff] [blame^] | 60 | # define DO_CRC(x) crc = tab[0][((crc >> 24) ^ (x)) & 255] ^ (crc << 8) |
| 61 | # define DO_CRC4 crc = tab[0][(crc) & 255] ^ \ |
| 62 | tab[1][(crc >> 8) & 255] ^ \ |
| 63 | tab[2][(crc >> 16) & 255] ^ \ |
| 64 | tab[3][(crc >> 24) & 255] |
Joakim Tjernlund | ddcaccb | 2009-12-14 18:01:33 -0800 | [diff] [blame] | 65 | # endif |
Joakim Tjernlund | 4f2a946 | 2010-03-05 13:43:55 -0800 | [diff] [blame] | 66 | const u32 *b; |
Joakim Tjernlund | ddcaccb | 2009-12-14 18:01:33 -0800 | [diff] [blame] | 67 | size_t rem_len; |
| 68 | |
| 69 | /* Align it */ |
Joakim Tjernlund | 4f2a946 | 2010-03-05 13:43:55 -0800 | [diff] [blame] | 70 | if (unlikely((long)buf & 3 && len)) { |
Joakim Tjernlund | ddcaccb | 2009-12-14 18:01:33 -0800 | [diff] [blame] | 71 | do { |
Joakim Tjernlund | 4f2a946 | 2010-03-05 13:43:55 -0800 | [diff] [blame] | 72 | DO_CRC(*buf++); |
| 73 | } while ((--len) && ((long)buf)&3); |
Joakim Tjernlund | ddcaccb | 2009-12-14 18:01:33 -0800 | [diff] [blame] | 74 | } |
| 75 | rem_len = len & 3; |
| 76 | /* load data 32 bits wide, xor data 32 bits wide. */ |
| 77 | len = len >> 2; |
Joakim Tjernlund | 4f2a946 | 2010-03-05 13:43:55 -0800 | [diff] [blame] | 78 | b = (const u32 *)buf; |
Joakim Tjernlund | ddcaccb | 2009-12-14 18:01:33 -0800 | [diff] [blame] | 79 | for (--b; len; --len) { |
| 80 | crc ^= *++b; /* use pre increment for speed */ |
Joakim Tjernlund | 836e2af | 2010-05-24 14:33:31 -0700 | [diff] [blame^] | 81 | DO_CRC4; |
Joakim Tjernlund | ddcaccb | 2009-12-14 18:01:33 -0800 | [diff] [blame] | 82 | } |
| 83 | len = rem_len; |
| 84 | /* And the last few bytes */ |
| 85 | if (len) { |
| 86 | u8 *p = (u8 *)(b + 1) - 1; |
| 87 | do { |
| 88 | DO_CRC(*++p); /* use pre increment for speed */ |
| 89 | } while (--len); |
| 90 | } |
| 91 | return crc; |
Joakim Tjernlund | 4f2a946 | 2010-03-05 13:43:55 -0800 | [diff] [blame] | 92 | #undef DO_CRC |
Joakim Tjernlund | 836e2af | 2010-05-24 14:33:31 -0700 | [diff] [blame^] | 93 | #undef DO_CRC4 |
Joakim Tjernlund | ddcaccb | 2009-12-14 18:01:33 -0800 | [diff] [blame] | 94 | } |
| 95 | #endif |
Randy Dunlap | 2f72100 | 2006-06-25 05:48:59 -0700 | [diff] [blame] | 96 | /** |
| 97 | * crc32_le() - Calculate bitwise little-endian Ethernet AUTODIN II CRC32 |
| 98 | * @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for |
| 99 | * other uses, or the previous crc32 value if computing incrementally. |
| 100 | * @p: pointer to buffer over which CRC is run |
| 101 | * @len: length of buffer @p |
| 102 | */ |
Ralf Baechle | e8c4431 | 2007-10-18 03:07:07 -0700 | [diff] [blame] | 103 | u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len); |
Randy Dunlap | 2f72100 | 2006-06-25 05:48:59 -0700 | [diff] [blame] | 104 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 105 | #if CRC_LE_BITS == 1 |
| 106 | /* |
| 107 | * In fact, the table-based code will work in this case, but it can be |
| 108 | * simplified by inlining the table in ?: form. |
| 109 | */ |
| 110 | |
Ralf Baechle | e8c4431 | 2007-10-18 03:07:07 -0700 | [diff] [blame] | 111 | u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 112 | { |
| 113 | int i; |
| 114 | while (len--) { |
| 115 | crc ^= *p++; |
| 116 | for (i = 0; i < 8; i++) |
| 117 | crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0); |
| 118 | } |
| 119 | return crc; |
| 120 | } |
| 121 | #else /* Table-based approach */ |
| 122 | |
Ralf Baechle | e8c4431 | 2007-10-18 03:07:07 -0700 | [diff] [blame] | 123 | u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 124 | { |
| 125 | # if CRC_LE_BITS == 8 |
Joakim Tjernlund | 836e2af | 2010-05-24 14:33:31 -0700 | [diff] [blame^] | 126 | const u32 (*tab)[] = crc32table_le; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 127 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 128 | crc = __cpu_to_le32(crc); |
Joakim Tjernlund | ddcaccb | 2009-12-14 18:01:33 -0800 | [diff] [blame] | 129 | crc = crc32_body(crc, p, len, tab); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 130 | return __le32_to_cpu(crc); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 131 | # elif CRC_LE_BITS == 4 |
| 132 | while (len--) { |
| 133 | crc ^= *p++; |
| 134 | crc = (crc >> 4) ^ crc32table_le[crc & 15]; |
| 135 | crc = (crc >> 4) ^ crc32table_le[crc & 15]; |
| 136 | } |
| 137 | return crc; |
| 138 | # elif CRC_LE_BITS == 2 |
| 139 | while (len--) { |
| 140 | crc ^= *p++; |
| 141 | crc = (crc >> 2) ^ crc32table_le[crc & 3]; |
| 142 | crc = (crc >> 2) ^ crc32table_le[crc & 3]; |
| 143 | crc = (crc >> 2) ^ crc32table_le[crc & 3]; |
| 144 | crc = (crc >> 2) ^ crc32table_le[crc & 3]; |
| 145 | } |
| 146 | return crc; |
| 147 | # endif |
| 148 | } |
| 149 | #endif |
| 150 | |
Randy Dunlap | 2f72100 | 2006-06-25 05:48:59 -0700 | [diff] [blame] | 151 | /** |
| 152 | * crc32_be() - Calculate bitwise big-endian Ethernet AUTODIN II CRC32 |
| 153 | * @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for |
| 154 | * other uses, or the previous crc32 value if computing incrementally. |
| 155 | * @p: pointer to buffer over which CRC is run |
| 156 | * @len: length of buffer @p |
| 157 | */ |
Ralf Baechle | e8c4431 | 2007-10-18 03:07:07 -0700 | [diff] [blame] | 158 | u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len); |
Randy Dunlap | 2f72100 | 2006-06-25 05:48:59 -0700 | [diff] [blame] | 159 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 160 | #if CRC_BE_BITS == 1 |
| 161 | /* |
| 162 | * In fact, the table-based code will work in this case, but it can be |
| 163 | * simplified by inlining the table in ?: form. |
| 164 | */ |
| 165 | |
Ralf Baechle | e8c4431 | 2007-10-18 03:07:07 -0700 | [diff] [blame] | 166 | u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 167 | { |
| 168 | int i; |
| 169 | while (len--) { |
| 170 | crc ^= *p++ << 24; |
| 171 | for (i = 0; i < 8; i++) |
| 172 | crc = |
| 173 | (crc << 1) ^ ((crc & 0x80000000) ? CRCPOLY_BE : |
| 174 | 0); |
| 175 | } |
| 176 | return crc; |
| 177 | } |
| 178 | |
| 179 | #else /* Table-based approach */ |
Ralf Baechle | e8c4431 | 2007-10-18 03:07:07 -0700 | [diff] [blame] | 180 | u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 181 | { |
| 182 | # if CRC_BE_BITS == 8 |
Joakim Tjernlund | 836e2af | 2010-05-24 14:33:31 -0700 | [diff] [blame^] | 183 | const u32 (*tab)[] = crc32table_be; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 184 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 185 | crc = __cpu_to_be32(crc); |
Joakim Tjernlund | ddcaccb | 2009-12-14 18:01:33 -0800 | [diff] [blame] | 186 | crc = crc32_body(crc, p, len, tab); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 187 | return __be32_to_cpu(crc); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 188 | # elif CRC_BE_BITS == 4 |
| 189 | while (len--) { |
| 190 | crc ^= *p++ << 24; |
| 191 | crc = (crc << 4) ^ crc32table_be[crc >> 28]; |
| 192 | crc = (crc << 4) ^ crc32table_be[crc >> 28]; |
| 193 | } |
| 194 | return crc; |
| 195 | # elif CRC_BE_BITS == 2 |
| 196 | while (len--) { |
| 197 | crc ^= *p++ << 24; |
| 198 | crc = (crc << 2) ^ crc32table_be[crc >> 30]; |
| 199 | crc = (crc << 2) ^ crc32table_be[crc >> 30]; |
| 200 | crc = (crc << 2) ^ crc32table_be[crc >> 30]; |
| 201 | crc = (crc << 2) ^ crc32table_be[crc >> 30]; |
| 202 | } |
| 203 | return crc; |
| 204 | # endif |
| 205 | } |
| 206 | #endif |
| 207 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 208 | EXPORT_SYMBOL(crc32_le); |
| 209 | EXPORT_SYMBOL(crc32_be); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 210 | |
| 211 | /* |
| 212 | * A brief CRC tutorial. |
| 213 | * |
| 214 | * A CRC is a long-division remainder. You add the CRC to the message, |
| 215 | * and the whole thing (message+CRC) is a multiple of the given |
| 216 | * CRC polynomial. To check the CRC, you can either check that the |
| 217 | * CRC matches the recomputed value, *or* you can check that the |
| 218 | * remainder computed on the message+CRC is 0. This latter approach |
| 219 | * is used by a lot of hardware implementations, and is why so many |
| 220 | * protocols put the end-of-frame flag after the CRC. |
| 221 | * |
| 222 | * It's actually the same long division you learned in school, except that |
| 223 | * - We're working in binary, so the digits are only 0 and 1, and |
| 224 | * - When dividing polynomials, there are no carries. Rather than add and |
| 225 | * subtract, we just xor. Thus, we tend to get a bit sloppy about |
| 226 | * the difference between adding and subtracting. |
| 227 | * |
| 228 | * A 32-bit CRC polynomial is actually 33 bits long. But since it's |
| 229 | * 33 bits long, bit 32 is always going to be set, so usually the CRC |
| 230 | * is written in hex with the most significant bit omitted. (If you're |
| 231 | * familiar with the IEEE 754 floating-point format, it's the same idea.) |
| 232 | * |
| 233 | * Note that a CRC is computed over a string of *bits*, so you have |
| 234 | * to decide on the endianness of the bits within each byte. To get |
| 235 | * the best error-detecting properties, this should correspond to the |
| 236 | * order they're actually sent. For example, standard RS-232 serial is |
| 237 | * little-endian; the most significant bit (sometimes used for parity) |
| 238 | * is sent last. And when appending a CRC word to a message, you should |
| 239 | * do it in the right order, matching the endianness. |
| 240 | * |
| 241 | * Just like with ordinary division, the remainder is always smaller than |
| 242 | * the divisor (the CRC polynomial) you're dividing by. Each step of the |
| 243 | * division, you take one more digit (bit) of the dividend and append it |
| 244 | * to the current remainder. Then you figure out the appropriate multiple |
| 245 | * of the divisor to subtract to being the remainder back into range. |
| 246 | * In binary, it's easy - it has to be either 0 or 1, and to make the |
| 247 | * XOR cancel, it's just a copy of bit 32 of the remainder. |
| 248 | * |
| 249 | * When computing a CRC, we don't care about the quotient, so we can |
| 250 | * throw the quotient bit away, but subtract the appropriate multiple of |
| 251 | * the polynomial from the remainder and we're back to where we started, |
| 252 | * ready to process the next bit. |
| 253 | * |
| 254 | * A big-endian CRC written this way would be coded like: |
| 255 | * for (i = 0; i < input_bits; i++) { |
| 256 | * multiple = remainder & 0x80000000 ? CRCPOLY : 0; |
| 257 | * remainder = (remainder << 1 | next_input_bit()) ^ multiple; |
| 258 | * } |
| 259 | * Notice how, to get at bit 32 of the shifted remainder, we look |
| 260 | * at bit 31 of the remainder *before* shifting it. |
| 261 | * |
| 262 | * But also notice how the next_input_bit() bits we're shifting into |
| 263 | * the remainder don't actually affect any decision-making until |
| 264 | * 32 bits later. Thus, the first 32 cycles of this are pretty boring. |
| 265 | * Also, to add the CRC to a message, we need a 32-bit-long hole for it at |
| 266 | * the end, so we have to add 32 extra cycles shifting in zeros at the |
| 267 | * end of every message, |
| 268 | * |
| 269 | * So the standard trick is to rearrage merging in the next_input_bit() |
| 270 | * until the moment it's needed. Then the first 32 cycles can be precomputed, |
| 271 | * and merging in the final 32 zero bits to make room for the CRC can be |
| 272 | * skipped entirely. |
| 273 | * This changes the code to: |
| 274 | * for (i = 0; i < input_bits; i++) { |
| 275 | * remainder ^= next_input_bit() << 31; |
| 276 | * multiple = (remainder & 0x80000000) ? CRCPOLY : 0; |
| 277 | * remainder = (remainder << 1) ^ multiple; |
| 278 | * } |
| 279 | * With this optimization, the little-endian code is simpler: |
| 280 | * for (i = 0; i < input_bits; i++) { |
| 281 | * remainder ^= next_input_bit(); |
| 282 | * multiple = (remainder & 1) ? CRCPOLY : 0; |
| 283 | * remainder = (remainder >> 1) ^ multiple; |
| 284 | * } |
| 285 | * |
| 286 | * Note that the other details of endianness have been hidden in CRCPOLY |
| 287 | * (which must be bit-reversed) and next_input_bit(). |
| 288 | * |
| 289 | * However, as long as next_input_bit is returning the bits in a sensible |
| 290 | * order, we can actually do the merging 8 or more bits at a time rather |
| 291 | * than one bit at a time: |
| 292 | * for (i = 0; i < input_bytes; i++) { |
| 293 | * remainder ^= next_input_byte() << 24; |
| 294 | * for (j = 0; j < 8; j++) { |
| 295 | * multiple = (remainder & 0x80000000) ? CRCPOLY : 0; |
| 296 | * remainder = (remainder << 1) ^ multiple; |
| 297 | * } |
| 298 | * } |
| 299 | * Or in little-endian: |
| 300 | * for (i = 0; i < input_bytes; i++) { |
| 301 | * remainder ^= next_input_byte(); |
| 302 | * for (j = 0; j < 8; j++) { |
| 303 | * multiple = (remainder & 1) ? CRCPOLY : 0; |
| 304 | * remainder = (remainder << 1) ^ multiple; |
| 305 | * } |
| 306 | * } |
| 307 | * If the input is a multiple of 32 bits, you can even XOR in a 32-bit |
| 308 | * word at a time and increase the inner loop count to 32. |
| 309 | * |
| 310 | * You can also mix and match the two loop styles, for example doing the |
| 311 | * bulk of a message byte-at-a-time and adding bit-at-a-time processing |
| 312 | * for any fractional bytes at the end. |
| 313 | * |
| 314 | * The only remaining optimization is to the byte-at-a-time table method. |
| 315 | * Here, rather than just shifting one bit of the remainder to decide |
| 316 | * in the correct multiple to subtract, we can shift a byte at a time. |
| 317 | * This produces a 40-bit (rather than a 33-bit) intermediate remainder, |
| 318 | * but again the multiple of the polynomial to subtract depends only on |
| 319 | * the high bits, the high 8 bits in this case. |
| 320 | * |
Joe Perches | 643d1f7 | 2008-02-03 17:48:52 +0200 | [diff] [blame] | 321 | * The multiple we need in that case is the low 32 bits of a 40-bit |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 322 | * value whose high 8 bits are given, and which is a multiple of the |
| 323 | * generator polynomial. This is simply the CRC-32 of the given |
| 324 | * one-byte message. |
| 325 | * |
| 326 | * Two more details: normally, appending zero bits to a message which |
| 327 | * is already a multiple of a polynomial produces a larger multiple of that |
| 328 | * polynomial. To enable a CRC to detect this condition, it's common to |
| 329 | * invert the CRC before appending it. This makes the remainder of the |
| 330 | * message+crc come out not as zero, but some fixed non-zero value. |
| 331 | * |
| 332 | * The same problem applies to zero bits prepended to the message, and |
| 333 | * a similar solution is used. Instead of starting with a remainder of |
| 334 | * 0, an initial remainder of all ones is used. As long as you start |
| 335 | * the same way on decoding, it doesn't make a difference. |
| 336 | */ |
| 337 | |
| 338 | #ifdef UNITTEST |
| 339 | |
| 340 | #include <stdlib.h> |
| 341 | #include <stdio.h> |
| 342 | |
| 343 | #if 0 /*Not used at present */ |
| 344 | static void |
| 345 | buf_dump(char const *prefix, unsigned char const *buf, size_t len) |
| 346 | { |
| 347 | fputs(prefix, stdout); |
| 348 | while (len--) |
| 349 | printf(" %02x", *buf++); |
| 350 | putchar('\n'); |
| 351 | |
| 352 | } |
| 353 | #endif |
| 354 | |
| 355 | static void bytereverse(unsigned char *buf, size_t len) |
| 356 | { |
| 357 | while (len--) { |
Akinobu Mita | 906d66d | 2006-12-08 02:36:25 -0800 | [diff] [blame] | 358 | unsigned char x = bitrev8(*buf); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 359 | *buf++ = x; |
| 360 | } |
| 361 | } |
| 362 | |
| 363 | static void random_garbage(unsigned char *buf, size_t len) |
| 364 | { |
| 365 | while (len--) |
| 366 | *buf++ = (unsigned char) random(); |
| 367 | } |
| 368 | |
| 369 | #if 0 /* Not used at present */ |
| 370 | static void store_le(u32 x, unsigned char *buf) |
| 371 | { |
| 372 | buf[0] = (unsigned char) x; |
| 373 | buf[1] = (unsigned char) (x >> 8); |
| 374 | buf[2] = (unsigned char) (x >> 16); |
| 375 | buf[3] = (unsigned char) (x >> 24); |
| 376 | } |
| 377 | #endif |
| 378 | |
| 379 | static void store_be(u32 x, unsigned char *buf) |
| 380 | { |
| 381 | buf[0] = (unsigned char) (x >> 24); |
| 382 | buf[1] = (unsigned char) (x >> 16); |
| 383 | buf[2] = (unsigned char) (x >> 8); |
| 384 | buf[3] = (unsigned char) x; |
| 385 | } |
| 386 | |
| 387 | /* |
| 388 | * This checks that CRC(buf + CRC(buf)) = 0, and that |
| 389 | * CRC commutes with bit-reversal. This has the side effect |
| 390 | * of bytewise bit-reversing the input buffer, and returns |
| 391 | * the CRC of the reversed buffer. |
| 392 | */ |
| 393 | static u32 test_step(u32 init, unsigned char *buf, size_t len) |
| 394 | { |
| 395 | u32 crc1, crc2; |
| 396 | size_t i; |
| 397 | |
| 398 | crc1 = crc32_be(init, buf, len); |
| 399 | store_be(crc1, buf + len); |
| 400 | crc2 = crc32_be(init, buf, len + 4); |
| 401 | if (crc2) |
| 402 | printf("\nCRC cancellation fail: 0x%08x should be 0\n", |
| 403 | crc2); |
| 404 | |
| 405 | for (i = 0; i <= len + 4; i++) { |
| 406 | crc2 = crc32_be(init, buf, i); |
| 407 | crc2 = crc32_be(crc2, buf + i, len + 4 - i); |
| 408 | if (crc2) |
| 409 | printf("\nCRC split fail: 0x%08x\n", crc2); |
| 410 | } |
| 411 | |
| 412 | /* Now swap it around for the other test */ |
| 413 | |
| 414 | bytereverse(buf, len + 4); |
Akinobu Mita | 906d66d | 2006-12-08 02:36:25 -0800 | [diff] [blame] | 415 | init = bitrev32(init); |
| 416 | crc2 = bitrev32(crc1); |
| 417 | if (crc1 != bitrev32(crc2)) |
Dominik Hackl | cfc646f | 2005-08-07 09:42:53 -0700 | [diff] [blame] | 418 | printf("\nBit reversal fail: 0x%08x -> 0x%08x -> 0x%08x\n", |
Akinobu Mita | 906d66d | 2006-12-08 02:36:25 -0800 | [diff] [blame] | 419 | crc1, crc2, bitrev32(crc2)); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 420 | crc1 = crc32_le(init, buf, len); |
| 421 | if (crc1 != crc2) |
| 422 | printf("\nCRC endianness fail: 0x%08x != 0x%08x\n", crc1, |
| 423 | crc2); |
| 424 | crc2 = crc32_le(init, buf, len + 4); |
| 425 | if (crc2) |
| 426 | printf("\nCRC cancellation fail: 0x%08x should be 0\n", |
| 427 | crc2); |
| 428 | |
| 429 | for (i = 0; i <= len + 4; i++) { |
| 430 | crc2 = crc32_le(init, buf, i); |
| 431 | crc2 = crc32_le(crc2, buf + i, len + 4 - i); |
| 432 | if (crc2) |
| 433 | printf("\nCRC split fail: 0x%08x\n", crc2); |
| 434 | } |
| 435 | |
| 436 | return crc1; |
| 437 | } |
| 438 | |
| 439 | #define SIZE 64 |
| 440 | #define INIT1 0 |
| 441 | #define INIT2 0 |
| 442 | |
| 443 | int main(void) |
| 444 | { |
| 445 | unsigned char buf1[SIZE + 4]; |
| 446 | unsigned char buf2[SIZE + 4]; |
| 447 | unsigned char buf3[SIZE + 4]; |
| 448 | int i, j; |
| 449 | u32 crc1, crc2, crc3; |
| 450 | |
| 451 | for (i = 0; i <= SIZE; i++) { |
| 452 | printf("\rTesting length %d...", i); |
| 453 | fflush(stdout); |
| 454 | random_garbage(buf1, i); |
| 455 | random_garbage(buf2, i); |
| 456 | for (j = 0; j < i; j++) |
| 457 | buf3[j] = buf1[j] ^ buf2[j]; |
| 458 | |
| 459 | crc1 = test_step(INIT1, buf1, i); |
| 460 | crc2 = test_step(INIT2, buf2, i); |
| 461 | /* Now check that CRC(buf1 ^ buf2) = CRC(buf1) ^ CRC(buf2) */ |
| 462 | crc3 = test_step(INIT1 ^ INIT2, buf3, i); |
| 463 | if (crc3 != (crc1 ^ crc2)) |
| 464 | printf("CRC XOR fail: 0x%08x != 0x%08x ^ 0x%08x\n", |
| 465 | crc3, crc1, crc2); |
| 466 | } |
| 467 | printf("\nAll test complete. No failures expected.\n"); |
| 468 | return 0; |
| 469 | } |
| 470 | |
| 471 | #endif /* UNITTEST */ |