32bit CRC

32bit CRC compatible with ZIP and ARJ

Contributor: SWAG SUPPORT TEAM

{
> I was kind of hoping to be ushered toward a File name I could locate
> which would do what I need. (Produce 32 bit CRC's that are compatible
> With PKZIP's output).

  I snagged this of this echo sometime ago. It does CRC32
 using only TP With the help of a precalculated table.
 It does procduce CRC32 values that are the same as PKZIP and ARJ.

--------------------- Unit CRC32C.PAS 8<-----------------------
{ Modified from a version posted on the Pascal echo by Floor
  A.C. Naaijkens (note introduction of a Constant and a
  Function and making the Array a Constant outside of
  crc32() which should improve speed a lot; further
  references made to a C version in a File of Snippets from the
(112 min left), (H)elp, More? C Echo marked as "Copyright (C) 1986 Gary S. Brown" (mostly to
  compare the large Arrays, which proved to be identical), and to
  "File verification using CRC" by Mark R. Nelson in Dr. Dobbs'
  Journal, May 1992. The latter provided the final piece of
  crucial information. Use: 1) Create a LongInt Variable For the
  CRC value; 2) Initialize this With CRCSeed; 3) Build the
  CRC Byte-by-Byte With CRC32(); 4) Finish With CRCend()
  (this was the part I found in Nelson). The result is a CRC
  value identical to that calculated by PKZip and ARJ.
}
Unit CRC32c;
Interface
  Const
    CRCSeed = $ffffffff;
    CRC32tab : Array[0..255] of LongInt = (
      $00000000, $77073096, $ee0e612c, $990951ba, $076dc419, $706af48f,
      $e963a535, $9e6495a3, $0edb8832, $79dcb8a4, $e0d5e91e, $97d2d988,
      $09b64c2b, $7eb17cbd, $e7b82d07, $90bf1d91, $1db71064, $6ab020f2,
      $f3b97148, $84be41de, $1adad47d, $6ddde4eb, $f4d4b551, $83d385c7,
      $136c9856, $646ba8c0, $fd62f97a, $8a65c9ec, $14015c4f, $63066cd9,
      $fa0f3d63, $8d080df5, $3b6e20c8, $4c69105e, $d56041e4, $a2677172,
      $3c03e4d1, $4b04d447, $d20d85fd, $a50ab56b, $35b5a8fa, $42b2986c,
      $dbbbc9d6, $acbcf940, $32d86ce3, $45df5c75, $dcd60dcf, $abd13d59,
      $26d930ac, $51de003a, $c8d75180, $bfd06116, $21b4f4b5, $56b3c423,
      $cfba9599, $b8bda50f, $2802b89e, $5f058808, $c60cd9b2, $b10be924,
      $2f6f7c87, $58684c11, $c1611dab, $b6662d3d, $76dc4190, $01db7106,
      $98d220bc, $efd5102a, $71b18589, $06b6b51f, $9fbfe4a5, $e8b8d433,
      $7807c9a2, $0f00f934, $9609a88e, $e10e9818, $7f6a0dbb, $086d3d2d,
      $91646c97, $e6635c01, $6b6b51f4, $1c6c6162, $856530d8, $f262004e,
      $6c0695ed, $1b01a57b, $8208f4c1, $f50fc457, $65b0d9c6, $12b7e950,
      $8bbeb8ea, $fcb9887c, $62dd1ddf, $15da2d49, $8cd37cf3, $fbd44c65,


      $4db26158, $3ab551ce, $a3bc0074, $d4bb30e2, $4adfa541, $3dd895d7,
      $a4d1c46d, $d3d6f4fb, $4369e96a, $346ed9fc, $ad678846, $da60b8d0,
      $44042d73, $33031de5, $aa0a4c5f, $dd0d7cc9, $5005713c, $270241aa,
      $be0b1010, $c90c2086, $5768b525, $206f85b3, $b966d409, $ce61e49f,
      $5edef90e, $29d9c998, $b0d09822, $c7d7a8b4, $59b33d17, $2eb40d81,
      $b7bd5c3b, $c0ba6cad, $edb88320, $9abfb3b6, $03b6e20c, $74b1d29a,
      $ead54739, $9dd277af, $04db2615, $73dc1683, $e3630b12, $94643b84,
      $0d6d6a3e, $7a6a5aa8, $e40ecf0b, $9309ff9d, $0a00ae27, $7d079eb1,
      $f00f9344, $8708a3d2, $1e01f268, $6906c2fe, $f762575d, $806567cb,
      $196c3671, $6e6b06e7, $fed41b76, $89d32be0, $10da7a5a, $67dd4acc,
      $f9b9df6f, $8ebeeff9, $17b7be43, $60b08ed5, $d6d6a3e8, $a1d1937e,
      $38d8c2c4, $4fdff252, $d1bb67f1, $a6bc5767, $3fb506dd, $48b2364b,
      $d80d2bda, $af0a1b4c, $36034af6, $41047a60, $df60efc3, $a867df55,
      $316e8eef, $4669be79, $cb61b38c, $bc66831a, $256fd2a0, $5268e236,
      $cc0c7795, $bb0b4703, $220216b9, $5505262f, $c5ba3bbe, $b2bd0b28,
      $2bb45a92, $5cb36a04, $c2d7ffa7, $b5d0cf31, $2cd99e8b, $5bdeae1d,
      $9b64c2b0, $ec63f226, $756aa39c, $026d930a, $9c0906a9, $eb0e363f,
      $72076785, $05005713, $95bf4a82, $e2b87a14, $7bb12bae, $0cb61b38,
      $92d28e9b, $e5d5be0d, $7cdcefb7, $0bdbdf21, $86d3d2d4, $f1d4e242,
      $68ddb3f8, $1fda836e, $81be16cd, $f6b9265b, $6fb077e1, $18b74777,
      $88085ae6, $ff0f6a70, $66063bca, $11010b5c, $8f659eff, $f862ae69,
      $616bffd3, $166ccf45, $a00ae278, $d70dd2ee, $4e048354, $3903b3c2,
      $a7672661, $d06016f7, $4969474d, $3e6e77db, $aed16a4a, $d9d65adc,
      $40df0b66, $37d83bf0, $a9bcae53, $debb9ec5, $47b2cf7f, $30b5ffe9,
      $bdbdf21c, $cabac28a, $53b39330, $24b4a3a6, $bad03605, $cdd70693,
      $54de5729, $23d967bf, $b3667a2e, $c4614ab8, $5d681b02, $2a6f2b94,
      $b40bbe37, $c30c8ea1, $5a05df1b, $2d02ef8d );
Function CRC32(value: Byte; crc: LongInt) : LongInt;
Function CRCend( crc : LongInt ) : LongInt ;

Implementation

Function CRC32(value: Byte; crc: LongInt) : LongInt;
begin
  CRC32 := CRC32tab[Byte(crc xor LongInt(value))] xor
           ((crc shr 8) and $00ffffff);
end;

Function CRCend( crc : LongInt ): LongInt;
begin
  CRCend := (crc xor CRCSeed);
end;

end.

{
Now to use it...

With a LongInt Variable, say vCRC32, first seed it
  vCRC32 := CRCSeed;
Then go Byte-by-Byte thorugh to calculate:
  For P := 1 to Size DO
    vCRC32 := CRC32(Bytes[P], vCRC32);

  Then finish it off With CRCend

    vCRC32 := CRCend(vCRC32);

  You should be able to Write your own Dec2Hex Function =)
}

 

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