Delphi dicas

Case com string

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Adicione esta classe ao seu projeto

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unit CRC;



interface



TYPE

        CRCTable    = ARRAY[1..32] OF BYTE;

        {yeah, yeah, it COULD be an array of integers .. but I used

        these two tables for something else later in my application.

        So I don't KNOW if it'll work as integers.  YOU try it.  [TH]

        }

        CONST

        crc  : INTEGER =    0;  {typed constant to force it into code segment}



        crctab : CRCTable =

        ($00,$00, $10,$81, $21,$02, $31,$83,

        $42,$04, $52,$85, $63,$06, $73,$87,

        $84,$08, $94,$89, $A5,$0A, $B5,$8B,

        $C6,$0C, $D6,$8D, $E7,$0E, $F7,$8F);



        crctb2 : CRCTable =

        ($00,$00, $11,$89, $23,$12, $32,$9B,

        $46,$24, $57,$AD, $65,$36, $74,$BF,

        $8C,$48, $9D,$C1, $AF,$5A, $BE,$D3,

        $CA,$6C, $DB,$E5, $E9,$7E, $F8,$F7);



        VAR

        crcval     : INTEGER Absolute crc;    {force it into code segment}



        PROCEDURE DoCRC(chrval : BYTE);

        {courtesy of MS-Kermit and Toad Hall, Nov 85}

        {computes ongoing CRC.  assumes CRC table has been

        established as a typed constant so CS can access it.

        Notice we aren't changing chrval at all .. just using

        it to modify our running crc value.

        }



        BEGIN

                inline

                ($2E/$8B/$16/crcval/    {mov dx,CS:crcval ;get current CRC value.}

                $8A/$86/chrval/         {mov al,chrval[BP] ; Get char ord  }

                $32/$C2/                {xor al,dl        ; Xor input with lo order

                byte of CRC.   }

                $8A/$E0/                {mov ah,al        ; Get a copy.    }

                $80/$E4/$F0/            {and ah,0F0H      ; Get hi 4 bits  }

                $B1/$04/                {mov cl,4                          }

                $D2/$EC/                {shr ah,cl        ; Right justify  }

                $24/$0F/                {and al,0FH       ; Get lo 4 bits  }

                $BE/crctb2/             {mov si,offset CS:crctb2 ; Low portion

                of CRC factor  }

                $B7/$00/                {mov bh,0                          }

                $8A/$D8/                {mov bl,al                         }

                $02/$D8/                {add bl,al        ; Get word index }

                $2E/$8B/$08/            {mov cx,CS:[si+bx] ; Low portion.  }

                $BE/crctab/             {mov si,offset CS:crctab ; High portion

                of CRC factor. }

                $B7/$00/                {mov bh,0                          }

                $8A/$DC/                {mov bl,ah                         }

                $02/$DC/                {add bl,ah        ; Get word index }

                $2E/$8B/$18/            {mov bx,CS:[si+bx]                 }

                $33/$D9/                {xor bx,cx        ; Add the two.   }

                $B1/$08/                {mov cl,8                          }

                $D3/$EA/                {shr dx,cl        ; Shift CRC 8 bits to the right.}

                $33/$D3/                {xor dx,bx        ; XOR table value and CRC.}

                $2E/$89/$16/crcval);    {mov CS:crcval,dx ; save new value }

        END;  {of DoCRC}

        ===========================================

        DICA: Use Assim...

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        procedure CompareStrings(S: String);

        begin

                case Crc32OfString(S) of

                Crc32OfString('Hello'): // Do wotever...

                Crc32OfString('Goodbye'): // Do wotever...

        end;

end;

por : Francis Reiner