Experimental Physics and
Industrial Control System

Marty Kraimer <[email protected]> · Fri, 30 Sep 2005 06:29:32 -0500

Andrew Johnson wrote:

Marty Kraimer wrote:

Thus all the IOC database needs is a:

1) nonmutable reference counted continguous string. When the

reference count goes to 0 the storage can be reclaimed

We might need more than one implementation of the nonmutable string;

one where the storage is obtained from the system (new/malloc), and a

second where the storage is a char* literal that must not be freed

when it's no longer referenced. Compiling DBD files generates

literals for record type names, field names and menu choice strings.

I think we should just store the char* pointer in these cases without

using any kind of string wrapper - if any reference count exists it

would have to apply to the descriptor as a whole, not just to the name

string.

I like the char * pointer for things like record type names, record

instance names, etc.(for java a regular String would accomplish the same

thing) This would take care of one main use of names

It does mean that we can not completely delete anything that has such

names because the storage for at least the name will remain. For example

we can not completely delete a record instance. I think this is OK.

In my design any const char* buffer or literal can be wrapped with a

ConstString at the point of use if it has to be passed to a routine

that takes a StringReader. Ownership would never be passed that way

though.

Can we accomplish the same thing without exposing the entire String class?

Something like:

interface DbInstance {
   ConstString *getName();
   ...
}

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System