Chapter 9

Although the preceding code is specific to the needs of Gnome::MIME, it dem 

onstrates a general technique for XS modules that link to external libraries. You'll 

typically need to add some custom Perl code to your Makefile.PL to check that the 

library you need exists and has the right version. Then you'll need to figure out 

what to set LIBS and INC to so that your module will compile and link successfully. 

Sometimes this will be a static string, but it's becoming more and more common 

for large projects to provide a binary like gnome config that makes determining 

these variables easier.

A First XSUB

The fundamental unit of an XS module is an XSUB. An XSUB is simply a defi 

nition of a single C function for which the xsubpp compiler will produce a Perl 

subroutine. The first XSUB I'll provide for Gnome::MIME is a wrapper for the 

gnome_mime_type() function. This function takes a single parameter, a filename, 

and returns its MIME type based on an examination of the filename alone. The 

C signature for gnome_mime_type() is as follows:

const char * gnome_mime_type(const gchar *filename);

Here is an XSUB that provides an interface to this function:

char *

gnome_mime_type(filename)

     char *filename

See Listing 9 4 for the new MIME.xs.

Listing 9 4. MIME.xs with First XSUB Added

#include "EXTERN.h"

#include "perl.h"

#include "XSUB.h"

MODULE = Gnome::MIME   PACKAGE = Gnome::MIME

char *

gnome_mime_type(filename)

     char * filename

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