153 lines
5.4 KiB
Plaintext
153 lines
5.4 KiB
Plaintext
unit CRC32Unit;
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{-------------------------------------------------------------------------------
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CRC32 Unit
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----------
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reSource v2.6
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Copyright (C) 1998-2001 Victor Kasenda / gruv
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http://go.to/gruv
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email: vickas@singnet.com.sg
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Taken from Swag:
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"Copyright (C) 1986 Gary S. Brown"
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"File verification using CRC" by Mark R. Nelson in Dr. Dobbs' Journal, May 1992.
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Delphi/Class conversion by Victor K / 1998
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Desc:
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Fast CRC-32 implementation using a table lookup.
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The table is generated by another program.
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Should be compatible or similar to the PKZip version.
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To use:
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1) Create the class
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2) Run through the buffer passing each byte to Update
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3) Get the crc-32
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Algo:
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crc_val: CRC value
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1) Seeds crc_val
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2) Uses a formula to update the crc_val
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3) Returns the current value of crc_val
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-------------------------------------------------------------------------------}
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(**) interface (**)
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uses Classes, StructsUnit;
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type
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TCRC32 = class
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private
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crc_val: Longword;
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public
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constructor Create;
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procedure Update(b: byte);
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function Get: Longword;
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end;
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procedure CalculateCRC32(block: PBlock; block_length: integer; var crc: longword);
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procedure CalculateCRC32Stream(Stream: TStream; len: integer; var crc: longword);
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(**) implementation (**)
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procedure CalculateCRC32(block: PBlock; block_length: integer; var crc: longword);
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var
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i: integer;
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CRC32: TCRC32;
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begin
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CRC32 := TCRC32.Create;
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for i := 0 to block_length-1 do
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CRC32.Update(block^[i]);
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crc := CRC32.Get;
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CRC32.Free;
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end;
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procedure CalculateCRC32Stream(Stream: TStream; len: integer; var crc: longword);
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var
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i: integer;
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CRC32: TCRC32;
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b: byte;
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begin
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CRC32 := TCRC32.Create;
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for i := 0 to len-1 do
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begin
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Stream.ReadBuffer(b, 1);
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CRC32.Update(b);
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end;
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crc := CRC32.Get;
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CRC32.Free;
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end;
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{-------------------------------------------------------------------------------
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CRC32 Class
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-------------------------------------------------------------------------------}
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Const
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CRCSeed = $ffffffff;
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CRC32tab : Array[0..255] of Longword = (
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$00000000, $77073096, $ee0e612c, $990951ba, $076dc419, $706af48f,
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$e963a535, $9e6495a3, $0edb8832, $79dcb8a4, $e0d5e91e, $97d2d988,
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$09b64c2b, $7eb17cbd, $e7b82d07, $90bf1d91, $1db71064, $6ab020f2,
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$f3b97148, $84be41de, $1adad47d, $6ddde4eb, $f4d4b551, $83d385c7,
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$136c9856, $646ba8c0, $fd62f97a, $8a65c9ec, $14015c4f, $63066cd9,
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$fa0f3d63, $8d080df5, $3b6e20c8, $4c69105e, $d56041e4, $a2677172,
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$3c03e4d1, $4b04d447, $d20d85fd, $a50ab56b, $35b5a8fa, $42b2986c,
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$dbbbc9d6, $acbcf940, $32d86ce3, $45df5c75, $dcd60dcf, $abd13d59,
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$26d930ac, $51de003a, $c8d75180, $bfd06116, $21b4f4b5, $56b3c423,
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$cfba9599, $b8bda50f, $2802b89e, $5f058808, $c60cd9b2, $b10be924,
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$2f6f7c87, $58684c11, $c1611dab, $b6662d3d, $76dc4190, $01db7106,
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$98d220bc, $efd5102a, $71b18589, $06b6b51f, $9fbfe4a5, $e8b8d433,
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$7807c9a2, $0f00f934, $9609a88e, $e10e9818, $7f6a0dbb, $086d3d2d,
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$91646c97, $e6635c01, $6b6b51f4, $1c6c6162, $856530d8, $f262004e,
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$6c0695ed, $1b01a57b, $8208f4c1, $f50fc457, $65b0d9c6, $12b7e950,
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$8bbeb8ea, $fcb9887c, $62dd1ddf, $15da2d49, $8cd37cf3, $fbd44c65,
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$4db26158, $3ab551ce, $a3bc0074, $d4bb30e2, $4adfa541, $3dd895d7,
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$a4d1c46d, $d3d6f4fb, $4369e96a, $346ed9fc, $ad678846, $da60b8d0,
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$44042d73, $33031de5, $aa0a4c5f, $dd0d7cc9, $5005713c, $270241aa,
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$be0b1010, $c90c2086, $5768b525, $206f85b3, $b966d409, $ce61e49f,
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$5edef90e, $29d9c998, $b0d09822, $c7d7a8b4, $59b33d17, $2eb40d81,
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$b7bd5c3b, $c0ba6cad, $edb88320, $9abfb3b6, $03b6e20c, $74b1d29a,
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$ead54739, $9dd277af, $04db2615, $73dc1683, $e3630b12, $94643b84,
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$0d6d6a3e, $7a6a5aa8, $e40ecf0b, $9309ff9d, $0a00ae27, $7d079eb1,
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$f00f9344, $8708a3d2, $1e01f268, $6906c2fe, $f762575d, $806567cb,
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$196c3671, $6e6b06e7, $fed41b76, $89d32be0, $10da7a5a, $67dd4acc,
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$f9b9df6f, $8ebeeff9, $17b7be43, $60b08ed5, $d6d6a3e8, $a1d1937e,
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$38d8c2c4, $4fdff252, $d1bb67f1, $a6bc5767, $3fb506dd, $48b2364b,
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$d80d2bda, $af0a1b4c, $36034af6, $41047a60, $df60efc3, $a867df55,
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$316e8eef, $4669be79, $cb61b38c, $bc66831a, $256fd2a0, $5268e236,
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$cc0c7795, $bb0b4703, $220216b9, $5505262f, $c5ba3bbe, $b2bd0b28,
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$2bb45a92, $5cb36a04, $c2d7ffa7, $b5d0cf31, $2cd99e8b, $5bdeae1d,
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$9b64c2b0, $ec63f226, $756aa39c, $026d930a, $9c0906a9, $eb0e363f,
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$72076785, $05005713, $95bf4a82, $e2b87a14, $7bb12bae, $0cb61b38,
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$92d28e9b, $e5d5be0d, $7cdcefb7, $0bdbdf21, $86d3d2d4, $f1d4e242,
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$68ddb3f8, $1fda836e, $81be16cd, $f6b9265b, $6fb077e1, $18b74777,
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$88085ae6, $ff0f6a70, $66063bca, $11010b5c, $8f659eff, $f862ae69,
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$616bffd3, $166ccf45, $a00ae278, $d70dd2ee, $4e048354, $3903b3c2,
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$a7672661, $d06016f7, $4969474d, $3e6e77db, $aed16a4a, $d9d65adc,
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$40df0b66, $37d83bf0, $a9bcae53, $debb9ec5, $47b2cf7f, $30b5ffe9,
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$bdbdf21c, $cabac28a, $53b39330, $24b4a3a6, $bad03605, $cdd70693,
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$54de5729, $23d967bf, $b3667a2e, $c4614ab8, $5d681b02, $2a6f2b94,
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$b40bbe37, $c30c8ea1, $5a05df1b, $2d02ef8d );
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constructor TCRC32.Create;
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begin
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inherited Create;
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crc_val := CRCSeed;
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end;
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procedure TCRC32.Update(b: byte);
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begin
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crc_val := CRC32tab[Byte(crc_val xor Longword(b))] xor ((crc_val shr 8) and $00ffffff);
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end;
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function TCRC32.Get: Longword;
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begin
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result := (crc_val xor CRCSeed)
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end;
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end.
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