Writing C Modules with XS

you'll receive this compilation error:

Error:  const gchar *  not in typemap in MIME.xs, line 10

Error:  const char *  not in typemap in MIME.xs, line 10

To use types that XS doesn't natively support, you need to create a new file 

called typemap in your module directory that contains code to translate to and from 

the new types. In this case, only two lines are required:

const char  *    T_PV

const gchar *    T_PV

This tells XS that const char * and const gchar * are both to be treated as T_PV,

which is the supplied typemap for char *. The T_PV typemap is defined in the system 

wide typemap file installed with Perl. You can find it in under the module directory 

for the ExtUtils modules in your Perl library. I'll explore typemaps in more detail 

later in this chapter.

The preceding code still doesn't work, though; it produces a syntax error 

because it doesn't recognize Gnome's gchar type. To fix this problem, I need to add 

an #include line below the three #includes already in the file:

#include "EXTERN.h"

#include "perl.h"

#include "XSUB.h"

#include 

This is part of the section before the MODULE command that is passed through to the 

generated MIME.c file verbatim.

Modifying the XSUB Name with PREFIX

Calling gnome_mime_type() from Perl with the XSUB shown earlier is done using a 

line that looks like this one:

my $type = Gnome::MIME::gnome_mime_type($filename);

This works just fine, but it's awfully verbose; the user is forced to type the 

words  Gnome  and  MIME  twice. One solution would be to export the function 

as is, but XS offers a simpler solution. By modifying the MODULE line, shown here:

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

21

217

7