Annotation of src/usr.bin/ssh/crc32.c, Revision 1.3
1.1 deraadt 1: /* The implementation here was originally done by Gary S. Brown. I have
2: borrowed the tables directly, and made some minor changes to the
3: crc32-function (including changing the interface). //ylo */
4:
5: #include "includes.h"
1.3 ! markus 6: RCSID("$Id: crc32.c,v 1.2 1999/10/01 18:18:40 deraadt Exp $");
1.1 deraadt 7:
8: #include "crc32.h"
9:
10: /* ============================================================= */
11: /* COPYRIGHT (C) 1986 Gary S. Brown. You may use this program, or */
12: /* code or tables extracted from it, as desired without restriction. */
13: /* */
14: /* First, the polynomial itself and its table of feedback terms. The */
15: /* polynomial is */
16: /* X^32+X^26+X^23+X^22+X^16+X^12+X^11+X^10+X^8+X^7+X^5+X^4+X^2+X^1+X^0 */
17: /* */
18: /* Note that we take it "backwards" and put the highest-order term in */
19: /* the lowest-order bit. The X^32 term is "implied"; the LSB is the */
20: /* X^31 term, etc. The X^0 term (usually shown as "+1") results in */
21: /* the MSB being 1. */
22: /* */
23: /* Note that the usual hardware shift register implementation, which */
24: /* is what we're using (we're merely optimizing it by doing eight-bit */
25: /* chunks at a time) shifts bits into the lowest-order term. In our */
26: /* implementation, that means shifting towards the right. Why do we */
27: /* do it this way? Because the calculated CRC must be transmitted in */
28: /* order from highest-order term to lowest-order term. UARTs transmit */
29: /* characters in order from LSB to MSB. By storing the CRC this way, */
30: /* we hand it to the UART in the order low-byte to high-byte; the UART */
31: /* sends each low-bit to hight-bit; and the result is transmission bit */
32: /* by bit from highest- to lowest-order term without requiring any bit */
33: /* shuffling on our part. Reception works similarly. */
34: /* */
35: /* The feedback terms table consists of 256, 32-bit entries. Notes: */
36: /* */
37: /* The table can be generated at runtime if desired; code to do so */
38: /* is shown later. It might not be obvious, but the feedback */
39: /* terms simply represent the results of eight shift/xor opera- */
40: /* tions for all combinations of data and CRC register values. */
41: /* */
42: /* The values must be right-shifted by eight bits by the "updcrc" */
43: /* logic; the shift must be unsigned (bring in zeroes). On some */
44: /* hardware you could probably optimize the shift in assembler by */
45: /* using byte-swap instructions. */
46: /* polynomial $edb88320 */
47: /* */
48: /* -------------------------------------------------------------------- */
49:
1.2 deraadt 50: static unsigned int crc32_tab[] = {
1.3 ! markus 51: 0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L,
! 52: 0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L,
! 53: 0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L,
! 54: 0x90bf1d91L, 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL,
! 55: 0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 0x136c9856L,
! 56: 0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L,
! 57: 0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L,
! 58: 0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,
! 59: 0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L,
! 60: 0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L, 0x26d930acL, 0x51de003aL,
! 61: 0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L,
! 62: 0xb8bda50fL, 0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L,
! 63: 0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL, 0x76dc4190L,
! 64: 0x01db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L, 0x06b6b51fL,
! 65: 0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L, 0x0f00f934L, 0x9609a88eL,
! 66: 0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L,
! 67: 0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL,
! 68: 0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L, 0x65b0d9c6L, 0x12b7e950L,
! 69: 0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L,
! 70: 0xfbd44c65L, 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L,
! 71: 0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL, 0x4369e96aL,
! 72: 0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L,
! 73: 0xaa0a4c5fL, 0xdd0d7cc9L, 0x5005713cL, 0x270241aaL, 0xbe0b1010L,
! 74: 0xc90c2086L, 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL,
! 75: 0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L, 0x59b33d17L,
! 76: 0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL, 0xedb88320L, 0x9abfb3b6L,
! 77: 0x03b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x04db2615L,
! 78: 0x73dc1683L, 0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L,
! 79: 0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L, 0xf00f9344L,
! 80: 0x8708a3d2L, 0x1e01f268L, 0x6906c2feL, 0xf762575dL, 0x806567cbL,
! 81: 0x196c3671L, 0x6e6b06e7L, 0xfed41b76L, 0x89d32be0L, 0x10da7a5aL,
! 82: 0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L,
! 83: 0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L,
! 84: 0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL, 0xd80d2bdaL, 0xaf0a1b4cL,
! 85: 0x36034af6L, 0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL,
! 86: 0x4669be79L, 0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L,
! 87: 0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL, 0xc5ba3bbeL,
! 88: 0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L, 0xb5d0cf31L,
! 89: 0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL,
! 90: 0x026d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L,
! 91: 0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L, 0x92d28e9bL,
! 92: 0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L, 0x86d3d2d4L, 0xf1d4e242L,
! 93: 0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L,
! 94: 0x18b74777L, 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL,
! 95: 0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L, 0xa00ae278L,
! 96: 0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L,
! 97: 0x4969474dL, 0x3e6e77dbL, 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L,
! 98: 0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L,
! 99: 0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L,
! 100: 0xcdd70693L, 0x54de5729L, 0x23d967bfL, 0xb3667a2eL, 0xc4614ab8L,
! 101: 0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL,
! 102: 0x2d02ef8dL
! 103: };
1.1 deraadt 104:
105: /* Return a 32-bit CRC of the contents of the buffer. */
106:
1.3 ! markus 107: unsigned int
! 108: crc32(const unsigned char *s, unsigned int len)
1.1 deraadt 109: {
1.3 ! markus 110: unsigned int i;
! 111: unsigned int crc32val;
! 112:
! 113: crc32val = 0;
! 114: for (i = 0; i < len; i ++) {
! 115: crc32val = crc32_tab[(crc32val ^ s[i]) & 0xff] ^ (crc32val >> 8);
! 116: }
! 117: return crc32val;
1.1 deraadt 118: }
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