德尔福5至2010年

Question

I used same function ( OneWayEncrypt(edit1.Text) ) in Delphi 5 and 2010.
Why the results are different? (Or how can I give the same results from Delphi 2010?)

uses Sysutils, Windows, Dialogs, classes;

function OneWayEncrypt(AStr: string): string;
PROCEDURE CalcCRC32 (p:  pointer; ByteCount:  DWORD; VAR CRCvalue:  DWORD);

implementation

const 
  table:  ARRAY[0..255] OF DWORD = 
  (
    //table consts are here
  );

PROCEDURE CalcCRC32(p: pointer; ByteCount: DWORD; VAR CRCvalue: DWORD);
VAR
  i: DWORD;
  q: ^Byte;
BEGIN
  q := p;
  FOR i := 0 TO ByteCount - 1 DO
  BEGIN
    CRCvalue := (CRCvalue SHR 8) XOR table[q^ XOR (CRCvalue AND $000000FF)];
    INC(q);
  END
END;

function OneWayEncrypt(AStr: string): string;
var
  dwCrc: DWORD;
  s: string;
begin
  dwCrc := $FFFFFFFF; 
  s := 'X' + AStr + '7F';
  CalcCRC32(Addr(s[1]), Length(s), dwCrc);
  result := IntToHex(dwCrc, 8);
end;

Answer 1

Are you aware that string refers to a Unicode string in D2010, while it refers to AnsiString in versions < D2009? That should be the source of your problem.

So you have two choices:

• You could replace all appearances of string with AnsiString . This should give you the same results as in D5, of course without Unicode support
• You could refactor your code. I guess that the pointer-"hacking" is the crucial part here. But I have to admit, I didn't take the time to fully understand the code ;-) (It could very well be that your code can't be used with Unicode anyways, due to the 255 consts = ISO8859?)

Answer 2

D2010 (and D2009) use Unicode strings (widestrings), so the character size is different (bytes). Try switching all references of string to AnsiString.

Answer 3

Minimal port, one line change:

  // old code:
  CalcCRC32(Addr(s[1]), Length(s), dwCrc);

  // delphi 2010 code:
  CalcCRC32( PAnsiChar(AnsiString(s)), Length(s), dwCrc);

Please be aware that any unicode content in the unicode "String" will be lost, but any ANSI (AZ, 1,3,4, you know) codepoints you used before, for example "Hello", should work just like before. Since this is a CRC32 algorithm, it could do a CRC32 on a UTF8 encoding of the string too, easily.