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roehrich@cray.com (Dean Roehrich)
Re: Passing a pointer to C function ?

Re: Passing a pointer to C function ?

Cray Research, Inc. 8 May 96 14:00:19 CDT
Newsgroups:
comp.lang.perl.misc
References:
<4mq340$jn7@thetimes.pixel.kodak.com>

In article <4mq340$jn7@thetimes.pixel.kodak.com>,
Tony Whyte  wrote:
>
>
>I have created an extension to a C program one of whose parameters is a 
>pointer to a particular type of data structure. I've created a typemap 
>entry of T_PTROBJ for the data structure (not sure if I had to since Im
>not really passing the structure itself)

T_PTROBJ, and similar maps, are used to handle the _pointer_ for the data
structure.  The basic form of these maps creates an SV and stores the value
of the pointer in that SV--a Perl object shadowing a C object.

> but Im not sure how I specify the 
>pointer parameter when calling the function from perl. I've CookbookB'd,
>and perldoc'd around  but cant find the trick. 

You cannot fabricate a pointer out of nothing.  Somehow you have to give
Perl the ability to allocate a copy of the structure and to get a pointer to
that structure.  The "Struct1" and "Opaque" examples in CookBookB cover this
basic case.

[posted&mailed]

Dean
roehrich@cray.com

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