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Re: Returning A Variable Length struct to IDL from C [message #27847 is a reply to message #27675]

Tue, 06 November 2001 05:36

Nigel Wade
Messages: 286
Registered: March 1998

Senior Member

Craig Markwardt wrote:

>
> Greetings--
>
> K Banerjee <kbanerje2@home.com> writes:
>
>> The next two lines are used to create the return value to IDL:
>>
>> void *psDef = IDL_MakeStruct(NULL, vbHeaderTags);
>> IDL_VPTR ivReturn = IDL_ImportArray(1, ilDims, IDL_TYP_STRUCT,
>> (UCHAR *) theHeaderActual, releaseMemory, psDef);
>
> Here is your first problem. IDL_ImportArray only works when you
> import static data, not dynamically allocated. Basically ImportArray
> only works once per piece of memory per IDL session.

Really?. I run code which calls IDL_ImportArray many 1000s of times within
a session, all with malloc'd data and have not had any problems.

Why do you think it can only be used once per session, with static data?

>
>> IDL_STRUCT_TAG_DEF vbHeaderTags[] =
>> {
>> {"VERS", 0, (void *) IDL_TYP_STRING},
>> {"USERHEADER", dims_user_header, (void *) IDL_TYP_STRING},
>> {"BYTEOFFSET", 0, (void *) IDL_TYP_LONG},
>> {0}
>> };
>
> Here (in my opinion) is your second problem: trying to do something
> too complicated within a DLM function. I personally think that while
> it's not impossible, trying to manipulate complex data structures
> within a DLM are very *close* to impossible and are really
> unnecessary.

No, no, no! You're missing the entire purpose of DLMs.
It's the realm of DLMs to do those things which are too complicated to do
in IDL. ;-)

--
-----------------------------------------------------------
Nigel Wade, System Administrator, Space Plasma Physics Group,
University of Leicester, Leicester, LE1 7RH, UK
E-mail : nmw@ion.le.ac.uk
Phone : +44 (0)116 2523568, Fax : +44 (0)116 2523555

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[Message index]

		Returning A Variable Length struct to IDL from C By: K Banerjee on Mon, 05 November 2001 11:05
		Re: Returning A Variable Length struct to IDL from C By: Nigel Wade on Wed, 07 November 2001 02:00
		Re: Returning A Variable Length struct to IDL from C By: Craig Markwardt on Tue, 06 November 2001 08:28
		Re: Returning A Variable Length struct to IDL from C By: Richard Younger on Tue, 06 November 2001 08:27
		Re: Returning A Variable Length struct to IDL from C By: Richard Younger on Tue, 06 November 2001 07:58
		Re: Returning A Variable Length struct to IDL from C By: Nigel Wade on Tue, 06 November 2001 05:36
		Re: Returning A Variable Length struct to IDL from C By: Nigel Wade on Tue, 06 November 2001 04:22
		Re: Returning A Variable Length struct to IDL from C By: Craig Markwardt on Mon, 05 November 2001 18:16

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