"Fossies" - the Fresh Open Source Software Archive

Member "tc-play-3.3/crc32.c" (2 Mar 2020, 5447 Bytes) of package /linux/misc/tc-play-3.3.tar.gz:


As a special service "Fossies" has tried to format the requested source page into HTML format using (guessed) C and C++ source code syntax highlighting (style: standard) with prefixed line numbers and code folding option. Alternatively you can here view or download the uninterpreted source code file. For more information about "crc32.c" see the Fossies "Dox" file reference documentation.

    1 /*-
    2  *  COPYRIGHT (C) 1986 Gary S. Brown.  You may use this program, or
    3  *  code or tables extracted from it, as desired without restriction.
    4  *
    5  *  First, the polynomial itself and its table of feedback terms.  The
    6  *  polynomial is
    7  *  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
    8  *
    9  *  Note that we take it "backwards" and put the highest-order term in
   10  *  the lowest-order bit.  The X^32 term is "implied"; the LSB is the
   11  *  X^31 term, etc.  The X^0 term (usually shown as "+1") results in
   12  *  the MSB being 1
   13  *
   14  *  Note that the usual hardware shift register implementation, which
   15  *  is what we're using (we're merely optimizing it by doing eight-bit
   16  *  chunks at a time) shifts bits into the lowest-order term.  In our
   17  *  implementation, that means shifting towards the right.  Why do we
   18  *  do it this way?  Because the calculated CRC must be transmitted in
   19  *  order from highest-order term to lowest-order term.  UARTs transmit
   20  *  characters in order from LSB to MSB.  By storing the CRC this way
   21  *  we hand it to the UART in the order low-byte to high-byte; the UART
   22  *  sends each low-bit to hight-bit; and the result is transmission bit
   23  *  by bit from highest- to lowest-order term without requiring any bit
   24  *  shuffling on our part.  Reception works similarly
   25  *
   26  *  The feedback terms table consists of 256, 32-bit entries.  Notes
   27  *
   28  *      The table can be generated at runtime if desired; code to do so
   29  *      is shown later.  It might not be obvious, but the feedback
   30  *      terms simply represent the results of eight shift/xor opera
   31  *      tions for all combinations of data and CRC register values
   32  *
   33  *      The values must be right-shifted by eight bits by the "updcrc
   34  *      logic; the shift must be unsigned (bring in zeroes).  On some
   35  *      hardware you could probably optimize the shift in assembler by
   36  *      using byte-swap instructions
   37  *      polynomial $edb88320
   38  */
   39 
   40 #include <stdlib.h>
   41 #include <stdint.h>
   42 #include "crc32.h"
   43 
   44 uint32_t crc32_tab[] = {
   45     0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
   46     0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
   47     0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2,
   48     0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
   49     0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
   50     0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
   51     0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c,
   52     0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
   53     0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423,
   54     0xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
   55     0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, 0x01db7106,
   56     0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
   57     0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d,
   58     0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
   59     0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
   60     0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
   61     0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7,
   62     0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
   63     0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa,
   64     0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
   65     0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
   66     0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
   67     0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84,
   68     0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
   69     0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
   70     0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
   71     0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e,
   72     0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
   73     0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55,
   74     0x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
   75     0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28,
   76     0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
   77     0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f,
   78     0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
   79     0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
   80     0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
   81     0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69,
   82     0x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
   83     0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc,
   84     0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
   85     0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693,
   86     0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
   87     0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
   88 };
   89 
   90 uint32_t
   91 crc32(const void *buf, size_t size)
   92 {
   93     const uint8_t *p;
   94     uint32_t crc;
   95 
   96     p = buf;
   97     crc = ~0U;
   98 
   99     while (size--)
  100         crc = crc32_tab[(crc ^ *p++) & 0xFF] ^ (crc >> 8);
  101 
  102     return crc ^ ~0U;
  103 }
  104 
  105 uint32_t
  106 crc32_intermediate(uint32_t crc, uint8_t d)
  107 {
  108     return crc32_tab[(crc ^ d) & 0xFF] ^ (crc >> 8);
  109 }