Calling builtin functions from Inline::C

[diotalevi]

This snippet show the original C code from zopen.c calling read() and then my substitute in some Inline::C code using perl's read(). I don't know that it is "ok" to call perl builtins from Inline::C by calling CORE:: functions. So is it? And is there a better way to write this?

    /* Check the magic number */
    if (read(zs->zs_fh, header, sizeof(header)) != sizeof(header) ||
        memcmp(header, z_magic, sizeof(z_magic)) != 0) {
        errno = EFTYPE;
        return (-1);
    }

    /* Check the magic number */
    Inline_Stack_Reset;
    Inline_Stack_Push(zs->zs_fh); /* a SV* of a IO handle passed in ea
+rlier */
    Inline_Stack_Push(header);
    Inline_Stack_Push(sizeof(header));
    perl_call_pv("CORE::read",G_SCALAR);
    read_rval = (ssize_t)POPi;
    Inline_Stack_Done;

    if (read_rval != sizeof(header) ||
        memcmp(header, z_magic, sizeof(z_magic)) != 0) {
        errno = EFTYPE;
        return (-1);
    }

[derby]

I don't know about better, it really all depends on how you're passing around zs and if/where it's being read in other parts of your code. If I was going to do this, I would either implement the reading in straight C or use PerlIO_read (perlapio) if portability is desired. And I know it's just a snippet but the one thing I would not do is return a -1 to the calling perl function - an undef is more idiomatic (&PL_sv_undef).

-derby

[diotalevi]

Ok, so if I use PerlIO_read() (the matching PerlIO call) that respects perlish filehandles where really they might be tied things, objects, actual filehandles, handles to *DATA, or other odd things? Or if I want to handle all the magic correctly do I just need to have a wrapper function like sub read { CORE::read( ... ) }?

[mpeppler]

I've not used Inline::C, but as someone who has messed with XS for quite a few years I'll second derby's comments - using straight C or PerlIO_read() sounds like a better solution here.

Michael

[diotalevi]

For anyone that is curious, it doesn't actually work to perl_call_cv("CORE::read",...). What the actual or best answer is... *shrug*. I dunno.