[fpc-devel] Unicode support (yet again)

[Hans-Peter Diettrich]

Luiz Americo Pereira Camara schrieb:

> The codepage of a RawByteString at runtime will keep the previous 
> CodePage (65001 for UTF8, 1200 for UTF16) as opposed to change to the 
> RawbyteString CodePage (65535) as a though previously

Delphi defines RawByteString=AnsiString, so there is no room for UTF-16 
in such an string.

> So the implementation would be:
> 
> function FileGetAttr(const FileName: RawByteString): Longint;
> begin
> SetCodePage(FileName, 1200, True);

Won't work, because of "const", and because UTF-16 is not a Byte 
(AnsiChar) string :-(

> Result:=Integer(Windows.GetFileAttributesW(PWideChar(FileName)));

Delphi would use
   Result:=Integer(Windows.GetFileAttributesW(PWideChar(string(FileName))));

with a temporary UnicodeString variable and an according try-finally block.

> end;
> 
> This way the version using UnicodeString parameter would have the 
> benefit of being less verbose and use the possible optimizations of the 
> implicit encoding conversion.

At best it *hides* the temporary variables and implicit conversions, but 
makes stringhandling more expensive. As I understand the FPC developers, 
they want to reduce the number of implicit string conversions, what can 
be achieved best with dedicated string types.

DoDi