| Importing data from C/C++ to IDL when type is only known at runtime [message #48536] |
Tue, 25 April 2006 13:29 |
kathryn.ksm
Messages: 10
Registered: April 2006
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Junior Member |
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Hi Folks,
I'm trying to write a DLM that uses existing C/C++ libaries to read
data in from files that have a custom (and fairly complex) format.
This is my first attempt at doing anything serious with IDL and I'm
having a hard time figuring out what's possible and what isn't. So far
most of what I've tried doesn't seem to be! So I could use some help.
My existing C code reads selected portions of the data files into a set
of arrays, where the data type is specified at run-time by the user.
So, on the C side of things, I have an array of void pointers that
point to dynamically allocated arrays with various types and sizes
depending on what the user asked for.
What I need to do is get this data into variables of appropriate types
in an interactive session in IDL. Ideally, what I would like to do is
to define and fill a set of nested structures in the DLM code at
run-time, and return a single structure variable to the IDL session.
This doesn't seem to be possible though. I can see how I could define
such a structure at run-time using an array of IDL_STRUCT_TAG_DEFs and
IDL_MakeStruct, but I don't see any way to fill that structure without
creating an analogous structure in C in advance (which doesn't seem
doable, but maybe I'm wrong about that).
A second approach I've considered is to return my array of arrays to
IDL, and to use a wrapper .pro routine to sort that into a structure.
Is there any way to return some kind of analogue to a void** from a
DLM? Or, in other words, is there any way that I can return an array
of arrays that have different types?
A third option that I've wondered about is if I could use a two-step
process: read in all of the information that I need to call something
like create_struct from the IDL side, and then pass the resulting
structure to my C function to actually read the data. Then I would
need to know how to get pointers to the structure's data elements from
within the DLM, which I'm not sure about either.
Sorry for the long-winded question, but I figure there are experts out
there who can easily see where I'm missing something. I'd be so
grateful for any help figuring out how to do this!
Many thanks,
Kathryn M.
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