| getting data from a pointer [message #12278] |
Tue, 21 July 1998 00:00 |
Vap User
Messages: 31
Registered: April 1998
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Here's a question for the assembled cognoscente.
When one creates a pointer one can escape the overhead of creating a
copy of the data by using the '/NO_COPY' keyword, e.g. if A =
some_really_Big_ARRAY then B = Ptr_New(A,/no_copy) will disattach the
data portion of A and attach it to B, thereby making A undefined, but
avoiding the wasteful copy of the data that was attached to A.
The question is: Is there a similar method to disattach the data
from a pointer and return it to a 'normal' IDL variable? Say one has
done the above, and now one has the variable B which points to the
data once contained in A, and one wants to reattach it to A but
without the 'copy'. I hope everyone would agree that
A = *B
Ptr_Free,B
will result in a copy of B's data being made in the first statement
before Ptr_Free is called to free the memory still retained by the
pointer B.
I thought that perhaps
A=temporary( *B )
Ptr_Free, B
will work, and want confirmation of this conjection.
If this method doesn't work, perhaps we could ask for this
functionality as an improvement?
Wadya think, Dave? (with the pipline to RSI)
I realize that there are many situation where I could do all
necessary operations on the pointer without every putting the data
back into a 'normal' IDL variable, thereby avoiding the problem. But
humor me and answer this question.
William Daffer
--
I don't speak for JPL, it doesn't speak for me.
Well, not all the time, at least.
William Daffer <vapuser@haifung.jpl.nasa.gov>
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