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Re: dlm returning ptr array and string array [message #34367 is a reply to message #34280]

Mon, 03 March 2003 12:00

Randall Skelton
Messages: 169
Registered: October 2000

Senior Member

I'll bite.

> I started a bit in dlm programming. Because of the latest bug in
> implementing the netCDF library I have to think in this case about getting
> more independent from rsi.

Re-implementing the interface to a file format such as netCDF would
probably be a fair amount of work.

> Now my questions:
> Is it possible to return a pointer vector by a dlm?

I am not entirely sure I understand what you are asking here. You cannot
create an IDL pointer in C, so if that is what you are asking you'll need
to rethink things. You can, create and return IDL variables and arrays of
any type (other than pointers). Likewise with structures but you cannot
directly interface these as objects (unless, of course, Ronn has some new
tricks to show us).

You can, however, allocate some very complex hash, linked-list, or other
structure that IDL has no knowledge about in C and pass a simple
string/index array back to IDL. You could even go as far as simply
keeping a hash table of indicies, strings, pointers and/or file offsets
that point to your data. Then when you want a specific data block, you
would use the name/index/??? and a separate c routine to return the block
as a structure or array. This is what diploma/co-op students are for ;)

> Could they freed by idl?

Again, there is no way to create or act on an IDL pointer in C. You can
create an return your large structure in C and then index it in IDL but
that isn't particularly clean or easy.

> Is this mostly stable?

Passing ordinary variables, arrays and structures is defined by the stable
DLM API. So, yes.

> Does it give memory leakage?

Depends how good of a C programmer you are ;)

> Are there memory limitiations generally using dlms?

Not really. Because DLMs are raw C code that are linked to IDL as shared
libraries, you basically have access to as much memory as you have
available. Once you allocate memory on the C side, you use various
components of the API to pass pointers to this memory so IDL knows about
it.

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[Message index]

		dlm returning ptr array and string array By: R.Bauer on Mon, 03 March 2003 02:26
		Re: dlm returning ptr array and string array By: Nigel Wade on Tue, 04 March 2003 03:03
		Re: dlm returning ptr array and string array By: R.Bauer on Tue, 04 March 2003 00:20
		Re: dlm returning ptr array and string array By: Randall Skelton on Mon, 03 March 2003 14:34
		Re: dlm returning ptr array and string array By: Mark Hadfield on Mon, 03 March 2003 12:22
		Re: dlm returning ptr array and string array By: R.Bauer on Mon, 03 March 2003 12:19
		Re: dlm returning ptr array and string array By: Randall Skelton on Mon, 03 March 2003 12:00

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