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