Hi monks, I need a bit of input here...

I am writing my first perl (V5.6.1) extension...
I am calling a C-function which returns a string in pre-allocated buffer,
like this:

// my_func() puts up to len bytes into buffer
int my_func(void *p_struct, char *buffer, int len)
[download]

Now, I want to call the function and return the buffer to my perl program.
My first shot at the XS code looked like this:

int
my_xs_func(p_struct, OUTLIST buffer, len)
        void *p_struct;
        char *buffer;
        int len;
    CODE:
        buffer = (char *)malloc(len);
        RETVAL = my_func(p_struct, buffer, len);
    OUTPUT:
        RETVAL
[download]

This returned my int return value and the buffer to my perl program...

Of course, calling malloc() without calling free() rang
the memory-leak bells. So I poked around for a way to
write the XS code so perl will know about the buffer I malloc'd
and GC the buffer automagically...

So now, my code looks like this:

int
my_xs_func(p_struct, OUTLIST buffer, len)
        void *p_struct;
        SV *buffer;
        int len;
    PREINIT:
        char *tmp_buffer;
    CODE:
        tmp_buffer = (char *)malloc(len);
        RETVAL = my_func(p_struct, tmp_buffer, len);
        buffer = sv_2mortal(newSVpv(tmp_buffer, 0));
        free(tmp_buffer);
    OUTPUT:
        RETVAL
[download]

I think this solves my memory-leak problem, but
I am by no means sure that this is the right way to do it.
I got to this solution by poking around in comp.lang.perl, and
in perlxs, perlguts, etc., with a healthy dose of trial-and-error.

Can someone tell me if I am going in the right direction, and give a few pointers?

Thanks!

3dan

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