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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 0000000..d95c6e3 --- /dev/null +++ b/fs/udf/crc.c @@ -0,0 +1,178 @@ +/* + * 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. + * + * CONTACTS + * E-mail regarding any portion of the Linux UDF file system should be + * directed to the development team mailing list (run by majordomo): + * linux_udf@hpesjro.fc.hp.com + * + * 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 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(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_crc16(bytes, sizeof bytes); + printf("udf_crc16: 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) */ |
