[Kst] New virtual method(s) in kstdatasource ?

[Nicolas.Brisset at eurocopter.com]

I wanted to implement support for a in-house format which I unfortunately 
cannot change and don't have the specs for. So I am stuck with the current 
library and have to use its functions. Now, there is the following problem: 
to get data I have to open the file with a function whose arguments contain 
the list of fields I'll be reading. As the open/close operations are awfully 
slow, it is not realistic to call the corresponding functions in each 
readField() call.
Would it be possible to add a new virtual method in kstdatasource that would 
be something like readList(const QStringList& fieldsToRead) and inform the 
datasource of the fields that are _going to be read_ before the calls to 
readField() happen ?
The base implementation could do nothing as existing datasources do not need 
this, but I can imagine it could be useful in other cases as well. Maybe we'd 
actually need two methods: one to add, the other to remove fields from the 
list of fields read from that source. It depends on the objects that manage 
these calls and I don't know how they work...

Nicolas