Question about sharing data structure in octave

[John W. Eaton]

On 27-Jun-2008, Michael Goffioul wrote:

| I would like to request some comments about the best way to
| implement shared data structure in octave. What I'm thinking
| about is to have a C++ object that I want to make accessible
| from the interpreter, through some octave_base_value inherited
| class. At the interpreter level, I want this data structure to act
| as a reference/pointer, not as a value: assigning to another
| variable would share the same data structure without copying
| it. This means in fine to use some reference counting. Now the
| question is where to implement this mechanism:
| 
| 1) octave_value uses sharing mechanism with its internal
| octave_base_value representation; so I could inherit from
| octave_base_value and implement my C++ data structure
| in it, using implicitly the octave_value reference counting.
| However, what I don't know is the situation where octave_value
| decides to clone/copy itself: it must do so, because by
| default octave deals with values and not references
| 
| 2) define 2 classes: one pure C++ to hold my data structure
| and is reference-counted, and one class inheriting from
| octave_base_value that contains the pure C++ object and
| handle the reference counting. This decouples completely
| the sharing mechanism with the one from octave_value,
| but increases the complexity and number of classes/objects

I'm not sure I understand precisely what it is you want to do, but
since the reference counting is managed in the octave_value class, why
not add a field that says what the copying policy should be, then use
that in the functions that manipulate the reference count?  Would that
work for what you want to do?

jwe