Experimental Physics and
Industrial Control System

Kay-Uwe Kasemir <[email protected]> · Wed, 20 Jul 2005 11:28:52 -0400

On Jul 20, 2005, at 11:12, Andrew Johnson wrote:

example where you actually need to destructively update a string..

stringCalc record...

...message-based device has to be able to create a new message every

time it processes

Very good examples!

How would you prefer to handle these?
a) equip the EpicsString class with all the methods
   to change/insert/delete character sequences at any
   position in the string
b) have a
      char buf[...]
   where you can to all the character fiddling,
   then attach a string interface to that in order
   to hand it to the CA Server or other EPICS entity?
   So this String class would actually be non-mutable,
   it only provides read-access to the user-owned buf.

I would prefer b, so we have another example for
my case that the most important task of the string class
it to interface with char *.

...segmented string requirement ... CA network input buffer, without

having to copy the character data at all

You're right that the string might arrive in pieces.
Just like the bytes of a double could be wrapped around
the network buffer boundary.

For a double, we expect CA to assemble the pieces back together
and hand us a usable number.
For the string, the end user also most likely needs the whole string.

Do you leave the assembly of strings, which logically ought to be hidden
in the network/middle ware layer, to the user?

-Kay

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System