On Sun, 19 Jun 2011, Mattias Gaertner wrote:
On Sun, 19 Jun 2011 11:28:22 +0200 (CEST)
Michael Van Canneyt <mich...@freepascal.org> wrote:
On Sat, 18 Jun 2011, Vladimir Zhirov wrote:
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?
Ansistring is not capable of keeping more than High(Integer) bytes.
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.
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.
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