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Re: CALL_EXTERNAL and memory allocation [message #29694 is a reply to message #29693]

Sun, 10 March 2002 13:42

Michael Zingale
Messages: 4
Registered: March 2002

Junior Member

I typically do something like the following:

in IDL:

string = ' '

ierr = call_external('lib.so', 'read_string', string)

and in C:

IDL_STRING* string = (IDL_STRING *) argv[0];

then fill string.s with the string.

To do an array of strings, it is a little more compilicated. If you do

unklabels = strarr(num),

you must initialize each string with a UNIQUE value, otherwise, IDL
gives them the same memory address. I do something like this:

unklabels = strarr(nvar)

; this is important -- each string must be initialized to a unique
; 'word', otherwise all the unklabels will share the same address in
; memory
for i = 0, nvar-1 do begin
unklabels[i] = string(i, format = '(i4)')
endfor

Then I can fill this in IDL w/o problems.

Mike

lyubo wrote:

> I have to get back a string from C, and if I have a null string
> defined in IDL and passed to C it won't work, because there
> isn't any memory allocated to the string.
>
> In general, how can I allocate memory for a string in IDL?
>
> lyubo
>
>
>
>
>
>
>

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[Message index]

		Re: CALL_EXTERNAL and memory allocation By: Michael Zingale on Mon, 11 March 2002 10:03
		Re: CALL_EXTERNAL and memory allocation By: James Kuyper on Mon, 11 March 2002 08:43
		Re: CALL_EXTERNAL and memory allocation By: Michael Zingale on Sun, 10 March 2002 15:43
		Re: CALL_EXTERNAL and memory allocation By: Michael Zingale on Sun, 10 March 2002 13:42
		Re: CALL_EXTERNAL and memory allocation By: Mark Rivers on Sat, 09 March 2002 09:42

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