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Array of Byte to PChar

I am converting a DLL to XE from D7 and need to convert an array of Byte that is passed in to a PChar that can be passed to a StrMove.

I could write my own ByteMove, but am needing a similar conversion in other spots that are more complicated to explain.

procedure Transpose(var Data, OrderData: array of Byte);
var
  TmpData: array[0..63] of Byte;
  i : Byte;
begin
  StrMove(@TmpData, @Data, SizeOf(Data));
  for i := 0 to High(OrderData) do
    Data[i] := TmpData[OrderData[i]];
end;

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With D7 this worked. But with the new PWideChar support in D2009+ it will not.

Geert G

the clue is what you are passing to this procedure
and what are you trying to accomplish ?

the context of what you are doing is odd for unicode strings

have you checked the functions StringOf and BytesOf ?

VahaC

in <=D2007 PChar = PAnsiChar, Char = AnsiChar
in D2009+ PChar = PWideChar, Char = WideChar

SizeOf(PAnsiChar) = 1Byte
SizeOf(PWideChar) = 2Byte

try to run this code in different versions of delphi

  ShowMessage(Format('Size of "AnsiChar" %d, Size of "WideChar" %d, Size of "Char" %d', [SizeOf(AnsiChar), SizeOf(WideChar), SizeOf(Char)]));

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VahaC

I wrote wrong

SizeOf(PAnsiChar) = 1Byte
SizeOf(PWideChar) = 2Byte

must be
SizeOf(AnsiChar) = 1Byte
SizeOf(WideChar) = 2Byte

GNiessen

ASKER

In this case I have a fixed Byte Array of 64 characters getting passed in from another system. There is some encryption being done that make accessing them as bytes more efficient then as an array of characters, This is legacy code, so it is all AnsiChar. I am not looking to make it Unicode enabled at this time.

brezniczky

I guess you only need to get rid of the string based approach, and handle data simply as bytes instead.

procedure Transpose(var Data, OrderData: array of Byte);
var
  TmpData: array[0..63] of Byte;
  i : Byte;
begin
  Move(Data, TmpData, SizeOf(Data));
  for i := 0 to High(OrderData) do
    Data[i] := TmpData[OrderData[i]];
end;

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It may worth thinking it over to pass PByte pointers to a function that expected PAnsiChar parameters, since it may lead to maintainability problems. I mean, finding a function with another parameter type is a good trail, even to another possible solution using the CopyMemory API as well.

brezniczky

Hello,

I guess you only need to get rid of the otherwise suspicious parameter passing - I mean, the StrMove expects PAnsiChars (in D7), so it should not deal with PByte pointers. You could move the data in a loop yourself byte by byte, or use one of the handful of functions like CopyMemory, MoveMemory, Move, etc..
As for me, I would prefer using Move as it seems to be the native solution:

procedure Transpose(var Data, OrderData: array of Byte);
var
  TmpData: array[0..63] of Byte;
  i : Byte;
begin
  Move(Data, TmpData, SizeOf(Data));
  for i := 0 to High(OrderData) do
    Data[i] := TmpData[OrderData[i]];
end;

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ThievingSix

" I mean, the StrMove expects PAnsiChars (in D7), so it should not deal with PByte pointers. "

Well, they are technically both pointers, hence why it works fine.

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brezniczky

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GNiessen

ASKER

While I agree with your comments on the ByteArray, sometimes there are reasons to not change things any more then required to make it work again. So I will go with the StrMove and PAnsiChar. Which was what I did and tested before, but was not sure it was the best or definitive solution. And this might not have been the best example of what I have in other areas, but seems to have worked.

Thanks