Delphi Magazine Collection 2001/Delphi Magazine Collection 20001 (2001).iso/DISKS/Issue30/diffm133/DIFFM133.ZIP/SOURCE/aCRC32.pas

Pascal/Delphi Source File | 1997-12-26 | 6.7 KB | 180 lines

{***********************************************}
{                                               }
{ CRC32 calculation V1.01                       }
{ Copyright (c) 1997 by S.Kurinny & S.Kostinsky }
{                                               }
{***********************************************}

unit aCRC32;

interface

{----------------------------------------------------------------------}

{ Tests CRC algorythm. Returns true if Ok. This function is for testing
  purposes only and you don't need to call it.}
Function  TestCRC:Boolean;

{ Finishes calculation of CRC. If you don't need compartability with PKZIP's
  CRC algorythm you may not call this function.}
function  CRC32Finish(CRC:Integer):Integer;

{ Returns initialized CRC variable ($FFFFFFFF). CRC variable should be
  initialized before calculating CRC.}
function  CRC32Start:Integer;

{ Calculates CRC for a given memory buffer. Buf  - memory buffer.
  CRC - initial CRC value (result of previuos call to CRC32Calc or $FFFFFFFF).
  BufSize - buffer size. Returns new CRC value.}
function  CRC32Calc(Var Buf;CRC:integer;BufSize:Integer):Integer;

{ Calculates CRC value for a given buffer. This function calls CRC32Start,
  CRC32Calc,CRC32 finish internally and returns calculated CRC value.}
Function  CalculateCRC32(VAR Buf;Count:Integer):Integer;

{----------------------------------------------------------------------}
implementation
{----------------------------------------------------------------------}

Function CalculateCRC32(VAR Buf;Count:Integer):Integer;
begin
  Result:=not CRC32Calc(Buf,$FFFFFFFF,Count);
end;

{----------------------------------------------------------------------}

const
  TestString: String[31] = 'Testing CRC32 routine ... ';
  PKZIP_CRC = $6759C95B;

{----------------------------------------------------------------------}

Const
aTableCRC32:Array[0..255] of integer=(
{;           $}
            $00000000, $77073096, $ee0e612c, $990951ba,
            $076dc419, $706af48f, $e963a535, $9e6495a3,
            $0edb8832, $79dcb8a4, $e0d5e91e, $97d2d988,
            $09b64c2b, $7eb17cbd, $e7b82d07, $90bf1d91,
{;            1}
            $1db71064, $6ab020f2, $f3b97148, $84be41de,
            $1adad47d, $6ddde4eb, $f4d4b551, $83d385c7,
            $136c9856, $646ba8c0, $fd62f97a, $8a65c9ec,
            $14015c4f, $63066cd9, $fa0f3d63, $8d080df5,
{;            2}
            $3b6e20c8, $4c69105e, $d56041e4, $a2677172,
            $3c03e4d1, $4b04d447, $d20d85fd, $a50ab56b,
            $35b5a8fa, $42b2986c, $dbbbc9d6, $acbcf940,
            $32d86ce3, $45df5c75, $dcd60dcf, $abd13d59,
{;            3}
            $26d930ac, $51de003a, $c8d75180, $bfd06116,
            $21b4f4b5, $56b3c423, $cfba9599, $b8bda50f,
            $2802b89e, $5f058808, $c60cd9b2, $b10be924,
            $2f6f7c87, $58684c11, $c1611dab, $b6662d3d,
{;            4}
            $76dc4190, $01db7106, $98d220bc, $efd5102a,
            $71b18589, $06b6b51f, $9fbfe4a5, $e8b8d433,
            $7807c9a2, $0f00f934, $9609a88e, $e10e9818,
            $7f6a0dbb, $086d3d2d, $91646c97, $e6635c01,
{;            5}
            $6b6b51f4, $1c6c6162, $856530d8, $f262004e,
            $6c0695ed, $1b01a57b, $8208f4c1, $f50fc457,
            $65b0d9c6, $12b7e950, $8bbeb8ea, $fcb9887c,
            $62dd1ddf, $15da2d49, $8cd37cf3, $fbd44c65,
{;            6}
            $4db26158, $3ab551ce, $a3bc0074, $d4bb30e2,
            $4adfa541, $3dd895d7, $a4d1c46d, $d3d6f4fb,
            $4369e96a, $346ed9fc, $ad678846, $da60b8d0,
            $44042d73, $33031de5, $aa0a4c5f, $dd0d7cc9,
{;            7}
            $5005713c, $270241aa, $be0b1010, $c90c2086,
            $5768b525, $206f85b3, $b966d409, $ce61e49f,
            $5edef90e, $29d9c998, $b0d09822, $c7d7a8b4,
            $59b33d17, $2eb40d81, $b7bd5c3b, $c0ba6cad,
{;            8}
            $edb88320, $9abfb3b6, $03b6e20c, $74b1d29a,
            $ead54739, $9dd277af, $04db2615, $73dc1683,
            $e3630b12, $94643b84, $0d6d6a3e, $7a6a5aa8,
            $e40ecf0b, $9309ff9d, $0a00ae27, $7d079eb1,
{;            9}
            $f00f9344, $8708a3d2, $1e01f268, $6906c2fe,
            $f762575d, $806567cb, $196c3671, $6e6b06e7,
            $fed41b76, $89d32be0, $10da7a5a, $67dd4acc,
            $f9b9df6f, $8ebeeff9, $17b7be43, $60b08ed5,
{;            A}
            $d6d6a3e8, $a1d1937e, $38d8c2c4, $4fdff252,
            $d1bb67f1, $a6bc5767, $3fb506dd, $48b2364b,
            $d80d2bda, $af0a1b4c, $36034af6, $41047a60,
            $df60efc3, $a867df55, $316e8eef, $4669be79,
{;            B}
            $cb61b38c, $bc66831a, $256fd2a0, $5268e236,
            $cc0c7795, $bb0b4703, $220216b9, $5505262f,
            $c5ba3bbe, $b2bd0b28, $2bb45a92, $5cb36a04,
            $c2d7ffa7, $b5d0cf31, $2cd99e8b, $5bdeae1d,
{;            C}
            $9b64c2b0, $ec63f226, $756aa39c, $026d930a,
            $9c0906a9, $eb0e363f, $72076785, $05005713,
            $95bf4a82, $e2b87a14, $7bb12bae, $0cb61b38,
            $92d28e9b, $e5d5be0d, $7cdcefb7, $0bdbdf21,
{;            D}
            $86d3d2d4, $f1d4e242, $68ddb3f8, $1fda836e,
            $81be16cd, $f6b9265b, $6fb077e1, $18b74777,
            $88085ae6, $ff0f6a70, $66063bca, $11010b5c,
            $8f659eff, $f862ae69, $616bffd3, $166ccf45,
{;            E}
            $a00ae278, $d70dd2ee, $4e048354, $3903b3c2,
            $a7672661, $d06016f7, $4969474d, $3e6e77db,
            $aed16a4a, $d9d65adc, $40df0b66, $37d83bf0,
            $a9bcae53, $debb9ec5, $47b2cf7f, $30b5ffe9,
{;            F}
            $bdbdf21c, $cabac28a, $53b39330, $24b4a3a6,
            $bad03605, $cdd70693, $54de5729, $23d967bf,
            $b3667a2e, $c4614ab8, $5d681b02, $2a6f2b94,
            $b40bbe37, $c30c8ea1, $5a05df1b, $2d02ef8d
);

{----------------------------------------------------------------------}
function CRC32Calc(Var Buf;CRC:integer;BufSize:Integer):Integer;assembler;
asm
  push esi
  mov esi,Buf
@1:
  movzx eax,byte ptr [esi]
  inc ESI
  xor al,dl
  shr edx,8
  xor edx,dword ptr [atablecrc32+eax*4]
  Loop @1
  mov eax,edx
  pop esi
end;

{----------------------------------------------------------------------}

Function TestCRC:Boolean;
Var
  CRC:Integer;
begin
  CRC:=not CRC32Calc(TestString[1],$ffffffff,Length(TestString));
  Result:=CRC=PKZIP_CRC;
end;

{----------------------------------------------------------------------}

function CRC32Finish(CRC:Integer):Integer;
begin
  Result := not CRC;
end;

{----------------------------------------------------------------------}

function CRC32Start:Integer;
begin
  Result := $FFFFFFFF;
end;

{----------------------------------------------------------------------}
end.