133 lines
6.6 KiB
Plaintext
133 lines
6.6 KiB
Plaintext
unit crc32a;
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{
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/* ============================================================= */
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/* COPYRIGHT (C) 1986 Gary S. Brown. You may use this program, or */
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/* code or tables extracted from it, as desired without restriction. */
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/* */
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/* First, the polynomial itself and its table of feedback terms. The */
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/* polynomial is */
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/* 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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/* */
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/* Note that we take it "backwards" and put the highest-order term in */
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/* the lowest-order bit. The X^32 term is "implied"; the LSB is the */
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/* X^31 term, etc. The X^0 term (usually shown as "+1") results in */
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/* the MSB being 1. */
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/* */
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/* Note that the usual hardware shift register implementation, which */
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/* is what we're using (we're merely optimizing it by doing eight-bit */
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/* chunks at a time) shifts bits into the lowest-order term. In our */
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/* implementation, that means shifting towards the right. Why do we */
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/* do it this way? Because the calculated CRC must be transmitted in */
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/* order from highest-order term to lowest-order term. UARTs transmit */
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/* characters in order from LSB to MSB. By storing the CRC this way, */
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/* we hand it to the UART in the order low-byte to high-byte; the UART */
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/* sends each low-bit to hight-bit; and the result is transmission bit */
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/* by bit from highest- to lowest-order term without requiring any bit */
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/* shuffling on our part. Reception works similarly. */
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/* */
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/* The feedback terms table consists of 256, 32-bit entries. Notes: */
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/* */
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/* The table can be generated at runtime if desired; code to do so */
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/* is shown later. It might not be obvious, but the feedback */
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/* terms simply represent the results of eight shift/xor opera- */
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/* tions for all combinations of data and CRC register values. */
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/* */
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/* The values must be right-shifted by eight bits by the "updcrc" */
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/* logic; the shift must be unsigned (bring in zeroes). On some */
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/* hardware you could probably optimize the shift in assembler by */
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/* using byte-swap instructions. */
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/* polynomial $edb88320 */
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/* */
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/* -------------------------------------------------------------------- */
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}
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interface
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type
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pbyte = ^byte;
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longrec = record
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lo,hi : word;
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end;
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var
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crc32val : longint;
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procedure updatecrc(s : pchar; len : integer);
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implementation
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const
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crc_32_tab : array[0..255] of longint = (
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$00000000, $77073096, $ee0e612c, $990951ba, $076dc419,
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$706af48f, $e963a535, $9e6495a3, $0edb8832, $79dcb8a4,
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$e0d5e91e, $97d2d988, $09b64c2b, $7eb17cbd, $e7b82d07,
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$90bf1d91, $1db71064, $6ab020f2, $f3b97148, $84be41de,
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$1adad47d, $6ddde4eb, $f4d4b551, $83d385c7, $136c9856,
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$646ba8c0, $fd62f97a, $8a65c9ec, $14015c4f, $63066cd9,
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$fa0f3d63, $8d080df5, $3b6e20c8, $4c69105e, $d56041e4,
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$a2677172, $3c03e4d1, $4b04d447, $d20d85fd, $a50ab56b,
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$35b5a8fa, $42b2986c, $dbbbc9d6, $acbcf940, $32d86ce3,
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$45df5c75, $dcd60dcf, $abd13d59, $26d930ac, $51de003a,
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$c8d75180, $bfd06116, $21b4f4b5, $56b3c423, $cfba9599,
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$b8bda50f, $2802b89e, $5f058808, $c60cd9b2, $b10be924,
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$2f6f7c87, $58684c11, $c1611dab, $b6662d3d, $76dc4190,
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$01db7106, $98d220bc, $efd5102a, $71b18589, $06b6b51f,
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$9fbfe4a5, $e8b8d433, $7807c9a2, $0f00f934, $9609a88e,
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$e10e9818, $7f6a0dbb, $086d3d2d, $91646c97, $e6635c01,
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$6b6b51f4, $1c6c6162, $856530d8, $f262004e, $6c0695ed,
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$1b01a57b, $8208f4c1, $f50fc457, $65b0d9c6, $12b7e950,
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$8bbeb8ea, $fcb9887c, $62dd1ddf, $15da2d49, $8cd37cf3,
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$fbd44c65, $4db26158, $3ab551ce, $a3bc0074, $d4bb30e2,
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$4adfa541, $3dd895d7, $a4d1c46d, $d3d6f4fb, $4369e96a,
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$346ed9fc, $ad678846, $da60b8d0, $44042d73, $33031de5,
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$aa0a4c5f, $dd0d7cc9, $5005713c, $270241aa, $be0b1010,
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$c90c2086, $5768b525, $206f85b3, $b966d409, $ce61e49f,
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$5edef90e, $29d9c998, $b0d09822, $c7d7a8b4, $59b33d17,
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$2eb40d81, $b7bd5c3b, $c0ba6cad, $edb88320, $9abfb3b6,
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$03b6e20c, $74b1d29a, $ead54739, $9dd277af, $04db2615,
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$73dc1683, $e3630b12, $94643b84, $0d6d6a3e, $7a6a5aa8,
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$e40ecf0b, $9309ff9d, $0a00ae27, $7d079eb1, $f00f9344,
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$8708a3d2, $1e01f268, $6906c2fe, $f762575d, $806567cb,
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$196c3671, $6e6b06e7, $fed41b76, $89d32be0, $10da7a5a,
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$67dd4acc, $f9b9df6f, $8ebeeff9, $17b7be43, $60b08ed5,
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$d6d6a3e8, $a1d1937e, $38d8c2c4, $4fdff252, $d1bb67f1,
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$a6bc5767, $3fb506dd, $48b2364b, $d80d2bda, $af0a1b4c,
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$36034af6, $41047a60, $df60efc3, $a867df55, $316e8eef,
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$4669be79, $cb61b38c, $bc66831a, $256fd2a0, $5268e236,
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$cc0c7795, $bb0b4703, $220216b9, $5505262f, $c5ba3bbe,
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$b2bd0b28, $2bb45a92, $5cb36a04, $c2d7ffa7, $b5d0cf31,
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$2cd99e8b, $5bdeae1d, $9b64c2b0, $ec63f226, $756aa39c,
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$026d930a, $9c0906a9, $eb0e363f, $72076785, $05005713,
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$95bf4a82, $e2b87a14, $7bb12bae, $0cb61b38, $92d28e9b,
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$e5d5be0d, $7cdcefb7, $0bdbdf21, $86d3d2d4, $f1d4e242,
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$68ddb3f8, $1fda836e, $81be16cd, $f6b9265b, $6fb077e1,
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$18b74777, $88085ae6, $ff0f6a70, $66063bca, $11010b5c,
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$8f659eff, $f862ae69, $616bffd3, $166ccf45, $a00ae278,
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$d70dd2ee, $4e048354, $3903b3c2, $a7672661, $d06016f7,
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$4969474d, $3e6e77db, $aed16a4a, $d9d65adc, $40df0b66,
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$37d83bf0, $a9bcae53, $debb9ec5, $47b2cf7f, $30b5ffe9,
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$bdbdf21c, $cabac28a, $53b39330, $24b4a3a6, $bad03605,
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$cdd70693, $54de5729, $23d967bf, $b3667a2e, $c4614ab8,
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$5d681b02, $2a6f2b94, $b40bbe37, $c30c8ea1, $5a05df1b,
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$2d02ef8d);
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procedure updatecrc(s : pchar; len : integer);
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(* update running CRC calculation with contents of a buffer *)
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var
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crcl : longrec absolute crc32val;
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x : integer;
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begin
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for x := 1 to len do
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begin
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crc32val := crc_32_tab[lo(crcl.lo) xor byte(s^)] xor ((crc32val
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shr 8) and $00ffffff);
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inc(s);
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end;
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end;
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end.
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