8a71ebf5bc
git-svn-id: https://svn.code.sf.net/p/kolmck/code@67 91bb2d04-0c0c-4d2d-88a5-bbb6f4c1fa07
81 lines
1.5 KiB
ObjectPascal
81 lines
1.5 KiB
ObjectPascal
unit UCRC;
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{$IFDEF FPC}
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{$MODE Delphi}
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{$ENDIF}
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interface
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uses KOL;
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type PCRC = ^TCRC;
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TCRC = object(TObj)
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public
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Value:integer;
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constructor Create;
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procedure _Init;
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procedure Update(const data: array of byte;const offset,size:integer);overload;
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procedure Update(const data: array of byte);overload;
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procedure UpdateByte(const b:integer);
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function GetDigest:integer;
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end;
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implementation
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var Table: array [0..255] of integer;
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constructor TCRC.Create;
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begin
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Value:=-1;
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end;
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procedure TCRC._Init;
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begin
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Value:=-1;
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end;
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procedure TCRC.Update(const data: array of byte;const offset,size:integer);
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var i:integer;
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begin
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for i := 0 to size-1 do
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value := Table[(value xor data[offset + i]) and $FF] xor (value shr 8);
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end;
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procedure TCRC.Update(const data: array of byte);
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var size:integer;
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i:integer;
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begin
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size := length(data);
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for i := 0 to size - 1 do
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value := Table[(value xor data[i]) and $FF] xor (value shr 8);
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end;
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procedure TCRC.UpdateByte(const b:integer);
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begin
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value := Table[(value xor b) and $FF] xor (value shr 8);
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end;
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function TCRC.GetDigest:integer;
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begin
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result:=value xor (-1);
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end;
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procedure InitCRC;
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var i,j,r:integer;
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begin
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for i := 0 to 255 do begin
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r := i;
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for j := 0 to 7 do begin
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if ((r and 1) <> 0) then
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r := (r shr 1) xor integer($EDB88320)
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else r := r shr 1;
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end;
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Table[i] := r;
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end;
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end;
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initialization
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InitCRC;
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end.
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