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Re: CALL_EXTERNAL and memory allocation [message #29693 is a reply to message #29682]

Sun, 10 March 2002 15:43

Michael Zingale
Messages: 4
Registered: March 2002

Junior Member

I should also point out that I have an example of reading a string from
an HDF5 dataset into IDL via call_external at the bottom of the
following page:

http://www.ucolick.org/~zingale/io_tutorial/

in the file idl_hdf5.tar

Mike

Michael Zingale wrote:

> 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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