Re: data access structures, strings

[Marty Kraimer <mrk@aps.anl.gov>]

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();
   ...
}