Hi,

Reviewing a bunch of my string processing functions made me wonder what integer type should I use for
position / length parameters.

I used to plain "Integer" for this task, but looking through RTL and LCL code I noticed that sometimes SizeInt and even PtrInt are also used:
- Length, Copy use Integer;
- Pos, Delete, Insert use SizeInt;
- UTF8Length, UTF8Pos, UTF8Copy, etc. use PtrInt.

PtrInt use seems to be generally discouraged by FPC docs but does it apply to this particular case?

The only benefit I see in SizeInt/PtrInt is larger size on 64-bit targets, that should theoretically make it possible to index larger strings. But is AnsiString type capable of holding more than High(Integer) bytes, or will it be so in the future?

Thus, the question basically is: what integer type is recommended to be used as index/length
for future-proof string processing functions?

Ansistring is not capable of keeping more than High(Integer) bytes.

Thus, the question basically is: what integer type is recommended to be used as index/length for future-proof string processing functions?

SizeInt should do just fine.

Michael.

That's not true. At least 3*high(integer) compiles and runs fine here on 64bit:

var
  s: ansistring;
begin
  SetLength(s,3*High(integer));
  s[length(s)]:='A';
  s[length(s)]:='B';
  writeln(s[length(s)],' ',length(s));
end.

I don't know where the real limit is.

Yes, because SizeInt is int64 under 64bit.

Mattias

Hm. I checked again.

Indeed, the hidden ansistring record contains
TAnsiRec = Packed Record
Ref,

     Len   : SizeInt;
     First : Char;
   end;

Which in fact means that the limit is the OS memory limit.

Michael.

Now it is no longer hidden. ;)

Mattias