Re: Pointer vs. BIF performance (was: Getting into pointers)

That reduces the source code but increases the amount of work being done.
Under the covers, %xlate would have to compare each character in the srcdata field with each character in the badchar field, one at a time. Most of the time it would not find a match, which means it would have searched the entire badchar field. Somewhere around 100,000 comparisons per srcdata field. Then there is the additional overhead for subsetting within the badchar field.

Contrast that with simply comparing each character to X'40', which is only 1920 comparisons.

Albert

----- Original Message -----
From: "Rory Hewitt" <roryhewitt@xxxxxxxxx>
To: "RPG programming on the IBM i / System i" <rpg400-l@xxxxxxxxxxxx>
Subject: Re: Pointer vs. BIF performance (was: Getting into pointers)
Date: Wed, 12 Aug 2009 09:53:29 -0700


Probably a very slight improvement. But on a string this long, is it worth
it?

Of course, you could simply use %xlate, specifying a string of control
characters for arg 1 and a string of blanks for arg 2:

D badchars C
x'0102030405060708090A0B0C0D10111213141516171819'

srcdta = %xlate( badchars : *blanks : SRCDTA );

I didn't put all of the badchars string in there, but you'd include all the
characters from x'01' to x'39' (not including x'0E' and x'0F', since they
are shift-in and shift-out DBCS characters).

I *think* using *blanks for arg 2 works, but you might need to define a
string of blanks the same length as badchars.

Rory

On Wed, Aug 12, 2009 at 7:42 AM, David Gibbs <david@xxxxxxxxxxxx> wrote:

This question is mostly out of idle curiosity ...

I've got a simple routine that is designed to replace any 5250 control
characters in a RPG source file with blank.

for p = 1 to %len(%trim(SRCDATA));
if %subst(SRCDATA:p:1) < x'40';
%subst(SRCDATA:p:1) = *blank;
endif;
endfor;

Would there be any performance benefit if I used a pointer to update the
field?

D charPtr S *
D char S 1A based(charPtr)

.
.
.

for p = 0 to %len(%trim(SRCDATA));
charPtr = %addr(SRCDATA)+p;
if char < x'40';
char = *blank;
endif;
endfor;

Thanks!

david

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