comp.lang.idl-pvwave archive: archive » Re: Can't pass data with CALL

Home » Public Forums » archive » Re: Can't pass data with CALL_EXTERNAL to C function

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: Can't pass data with CALL_EXTERNAL to C function [message #60835 is a reply to message #60832]

Fri, 20 June 2008 07:56

Trae
Messages: 23
Registered: May 2007

Junior Member

Dan,

In your call to call_external I don't see that you set the VALUE
keyword. This is what tells call_external which parameters you are
passing via value and which via reference. This may be the cause of
your problems. Whenever I am forced to use call_external, I set this
keyword manually,

From the help manual:

VALUE
A byte array, with as many elements as there are optional parameters,
indicating the method of parameter passing. Arrays are always passed
by reference. If parameter Pi is a scalar, it is passed by reference
if VALUE[i] is 0; and by value if it is non-zero. There are some
restrictions on data types that should be considered when using this
keyword, as discussed below.

As Brian noted, using call_external can be a beast. We worked on a
project for a week, before I concluded that it was much faster (and
easier) to rewrite the offending C code in IDL. Many a frustration
beer was drunk that day. :)

Good Luck!
-Trae

On Jun 19, 3:32 pm, Dan <daniel.dex...@colorado.edu> wrote:
> Hi Brian,
>
> Thanks for the tutorial, but I couldn't figure out how to make it work
> for my C code. In particular, none of the pointers work, not just the
> ones for the multi-D arrays.
>
> Could you (or someone) please clarify how you got pass by reference to
> work.
>
> Thanks again,
> -Dan

Report message to a moderator

[Message index]

		Re: Can't pass data with CALL_EXTERNAL to C function By: Dan[1] on Fri, 20 June 2008 10:30
		Re: Can't pass data with CALL_EXTERNAL to C function By: Trae on Fri, 20 June 2008 07:56
		Re: Can't pass data with CALL_EXTERNAL to C function By: Allan Whiteford on Fri, 20 June 2008 04:18
		Re: Can't pass data with CALL_EXTERNAL to C function By: Brian Larsen on Thu, 19 June 2008 14:27
		Re: Can't pass data with CALL_EXTERNAL to C function By: Dan[1] on Thu, 19 June 2008 12:32
		Re: Can't pass data with CALL_EXTERNAL to C function By: Brian Larsen on Thu, 19 June 2008 11:46

Previous Topic:	Re: Implementation of G Statistic in IDL
Next Topic:	Multidimensional arrays and CALL_EXTERNAL

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Wed Oct 08 19:58:53 PDT 2025

Total time taken to generate the page: 0.00374 seconds