source: trunk/third/ssh/crc32.c @ 12646

Revision 12646, 7.4 KB checked in by danw, 26 years ago (diff)
This commit was generated by cvs2svn to compensate for changes in r12645, which included commits to RCS files with non-trunk default branches.
Line 
1/*
2 * $Id: crc32.c,v 1.1.1.2 1999-03-08 17:43:17 danw Exp $
3 * $Log: not supported by cvs2svn $
4 * Revision 1.1.1.1  1996/02/18  21:38:12  ylo
5 *      Imported ssh-1.2.13.
6 *
7 * Revision 1.2  1995/07/13  01:21:34  ylo
8 *      Added cvs log.
9 *
10 * $Endlog$
11 */
12
13/* The implementation here was originally done by Gary S. Brown.  I have
14   borrowed the tables directly, and made some minor changes to the
15   crc32-function (including changing the interface). //ylo */
16
17#include "crc32.h"
18
19  /* ============================================================= */
20  /*  COPYRIGHT (C) 1986 Gary S. Brown.  You may use this program, or       */
21  /*  code or tables extracted from it, as desired without restriction.     */
22  /*                                                                        */
23  /*  First, the polynomial itself and its table of feedback terms.  The    */
24  /*  polynomial is                                                         */
25  /*  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   */
26  /*                                                                        */
27  /*  Note that we take it "backwards" and put the highest-order term in    */
28  /*  the lowest-order bit.  The X^32 term is "implied"; the LSB is the     */
29  /*  X^31 term, etc.  The X^0 term (usually shown as "+1") results in      */
30  /*  the MSB being 1.                                                      */
31  /*                                                                        */
32  /*  Note that the usual hardware shift register implementation, which     */
33  /*  is what we're using (we're merely optimizing it by doing eight-bit    */
34  /*  chunks at a time) shifts bits into the lowest-order term.  In our     */
35  /*  implementation, that means shifting towards the right.  Why do we     */
36  /*  do it this way?  Because the calculated CRC must be transmitted in    */
37  /*  order from highest-order term to lowest-order term.  UARTs transmit   */
38  /*  characters in order from LSB to MSB.  By storing the CRC this way,    */
39  /*  we hand it to the UART in the order low-byte to high-byte; the UART   */
40  /*  sends each low-bit to hight-bit; and the result is transmission bit   */
41  /*  by bit from highest- to lowest-order term without requiring any bit   */
42  /*  shuffling on our part.  Reception works similarly.                    */
43  /*                                                                        */
44  /*  The feedback terms table consists of 256, 32-bit entries.  Notes:     */
45  /*                                                                        */
46  /*      The table can be generated at runtime if desired; code to do so   */
47  /*      is shown later.  It might not be obvious, but the feedback        */
48  /*      terms simply represent the results of eight shift/xor opera-      */
49  /*      tions for all combinations of data and CRC register values.       */
50  /*                                                                        */
51  /*      The values must be right-shifted by eight bits by the "updcrc"    */
52  /*      logic; the shift must be unsigned (bring in zeroes).  On some     */
53  /*      hardware you could probably optimize the shift in assembler by    */
54  /*      using byte-swap instructions.                                     */
55  /*      polynomial $edb88320                                              */
56  /*                                                                        */
57  /*  --------------------------------------------------------------------  */
58
59static unsigned long crc32_tab[] = {
60      0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L,
61      0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L,
62      0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L,
63      0x90bf1d91L, 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL,
64      0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 0x136c9856L,
65      0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L,
66      0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L,
67      0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,
68      0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L,
69      0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L, 0x26d930acL, 0x51de003aL,
70      0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L,
71      0xb8bda50fL, 0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L,
72      0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL, 0x76dc4190L,
73      0x01db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L, 0x06b6b51fL,
74      0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L, 0x0f00f934L, 0x9609a88eL,
75      0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L,
76      0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL,
77      0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L, 0x65b0d9c6L, 0x12b7e950L,
78      0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L,
79      0xfbd44c65L, 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L,
80      0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL, 0x4369e96aL,
81      0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L,
82      0xaa0a4c5fL, 0xdd0d7cc9L, 0x5005713cL, 0x270241aaL, 0xbe0b1010L,
83      0xc90c2086L, 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL,
84      0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L, 0x59b33d17L,
85      0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL, 0xedb88320L, 0x9abfb3b6L,
86      0x03b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x04db2615L,
87      0x73dc1683L, 0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L,
88      0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L, 0xf00f9344L,
89      0x8708a3d2L, 0x1e01f268L, 0x6906c2feL, 0xf762575dL, 0x806567cbL,
90      0x196c3671L, 0x6e6b06e7L, 0xfed41b76L, 0x89d32be0L, 0x10da7a5aL,
91      0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L,
92      0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L,
93      0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL, 0xd80d2bdaL, 0xaf0a1b4cL,
94      0x36034af6L, 0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL,
95      0x4669be79L, 0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L,
96      0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL, 0xc5ba3bbeL,
97      0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L, 0xb5d0cf31L,
98      0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL,
99      0x026d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L,
100      0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L, 0x92d28e9bL,
101      0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L, 0x86d3d2d4L, 0xf1d4e242L,
102      0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L,
103      0x18b74777L, 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL,
104      0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L, 0xa00ae278L,
105      0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L,
106      0x4969474dL, 0x3e6e77dbL, 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L,
107      0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L,
108      0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L,
109      0xcdd70693L, 0x54de5729L, 0x23d967bfL, 0xb3667a2eL, 0xc4614ab8L,
110      0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL,
111      0x2d02ef8dL
112   };
113
114/* Return a 32-bit CRC of the contents of the buffer. */
115
116unsigned long crc32(const unsigned char *s, unsigned int len)
117{
118  unsigned int i;
119  unsigned long crc32val;
120 
121  crc32val = 0;
122  for (i = 0;  i < len;  i ++)
123    {
124      crc32val =
125        crc32_tab[(crc32val ^ s[i]) & 0xff] ^
126          (crc32val >> 8);
127    }
128  return crc32val;
129}
Note: See TracBrowser for help on using the repository browser.