[fpc-pascal] string concatenation speed

[Marc Santhoff]

Am Dienstag, den 21.06.2005, 21:19 +0200 schrieb Leonhard Holz:
> Hi,

Hi Leo,

> > 
> > if (sl[4] <> '') then
> > 		if ((sl[4][1] = '"') AND (sl[4][length(sl[4])] = '"'))
> > 			then BaseColor := copy(sl[4],2,length(sl[4])-2) else BaseColor :=
> > sl[4];
> 
> You can tweak this a little by storing sl[4] and length(sl[4]) in local 
> vars, but the whole approach tends to be slow. If you want it faster, 
> dont allocate memory ("copy" & ":=" on the stack) and dont move string 
> data. This could be done by "translating" BaseColor to an int or so.
> Either case you should not to use the StringList - read out BaseColor 
> (and the other fields) directly from the source, skipping the " at reading.

I'm trying local temporary vars next, time measuring code is already in.

> > Another snippet esecially for concatenation is this:
> > 
> > result := 	IntToStr(ID) + SEP + 
> > 		IntToStr(ID_Customer) + SEP +
> > 		QT + Treatment + QT + SEP +
> > 		DateToStr(Date) + SEP + 
> > 		QT + BaseColor + QT + SEP +
> > ... and so on for approx. 15 fields
> 
> Same as above - try to avoid the concatenation. What do you do with 
> result? If you write it to a file, write it directly. If you echo it 
> somewhere, echo it directly. If you pass it to another function, make it 
>   a record with pointers to the string data.

Since I'm lazy and love the TStringList since Delphi 1 I do not write at
all myself but let the stringlist do it (saveToFile / loadFromFile). ;)

But I have to validate my habits anew in this case.

Thank you, I stand corrected,
Marc