Experimental Physics and
Industrial Control System

Kay-Uwe Kasemir <[email protected]> · Wed, 20 Jul 2005 08:59:02 -0400

Hi:

On Jul 19, 2005, at 17:49, Benjamin Franksen wrote:

do you know any example where you actually need to destructively

update a string,

once you have it constructed?

I think Ben is right here.
The only in-place update of a string that comes to my mind
is toupper()/tolower() type of formatting,
which often can be avoided by leaving the string as-is
and using a compare_ignorecase().

Most of the time (at least in the IOC, but I believe this is true for
most clients, too) strings are merely copied from one place to another,
or else newly constructed from existing pieces.

Exactly right, with the added constraint that you need
a (const char *) somewhere in the copy chain:

 callback with new data for a channel
 -> copy string as (char *) into display widget

 User enters something in text box
 -> extract (char *) from widget and pass as EpicsString
    to CA 'write' routine.

I think we need to concentrate on the 99% where the string
is a short, contiguous (char *),
instead of the 1% where the string
is 1MB long, stored as non-contiguous 10 byte segments.

I  doubt that write access is needed at arbitrary positions. Having the
write position fixed at the end of the string under construction is
general enough for any application I can think of.

Here I think the most common cases are
- sprintf-type formatting of the whole string
- repeated concatenation to the end of the string.

Thanks,
Kay

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System