Talk:FPC Unicode support

Irrelevant stuff - looks like a wish list

Removed this from the main page as it will only give cause for confusion. Developers agree it is useless: http://www.mail-archive.com/fpc-devel@lists.freepascal.org/msg30196.html

IMO this can be deleted from this page as well.

Thanks, --BigChimp 16:08, 7 January 2014 (CET)

FPC Unicode support

FPC must have the following string types with transparent conversion between them (like current AnsiString <-> WideString conversion):

• shortstring
• ansistring
• widestring
• utf8string
• utf16string
• utf32string
• ucs2string (?)
• ucs4string (?)

Development and further maintenance of these string types must be as simple as possible. New string types must be easily added in future if needed.

Compiler uses generic structure and helper routines to handle all refcounted string types.

String header:

type
  TRefStringRec = packed record
    Encoding: word;    // encoding of string
    ElementSize: byte; // size in bytes of string's element (1-4)
    Ref: SizeInt;      // number of references
    Len: SizeInt;      // number of elements is string 
  end;

Helper routines will know how to handle string from its header.

Extra parameter with string type information is passed to some routines (like fpc_RefString_SetLength) to allow properly initialize new strings.

widestring type on Windows targets remains non-refcounted and OLE compatible. Minimal number of helper routines is used for it. On non-Windows targets widestring is alias to utf16string.

The compiler uses helpers for string type conversions like this:

procedure fpc_ansistring_to_utf16string(out dst: utf16string; const src: ansistring);
procedure fpc_utf32string_to_utf16string(out dst: utf16string; const src: utf32string);

The compiler generates helper procedure name from type names. The compiler does not perform any string conversion handling by itself.