# The following was supposedly scribed by
# Wu, Gang \(Steven\)
# on Thursday 25 March 2004 08:46 pm:
|I am not sure how to do it in the way you just suggested. Can you
|enlighten me a bit, in terms of using separate C and Perl modules?
You've just got to have two modules which declare themselves as the same
package name. One of these is written purely in perl, and the other uses
Inline::C. You put them in two files which end in .pm and are in one of the
@INC directories (or another directory which can be added with 'use lib' or
the environment variable $PERL5LIB = 'directory/")
If you want a function-call based interface, you would have to call all of
your functions with PackageName::function(), but you might be able to manage
it somehow with an import() sub (or the dirty trick of declaring 'package
main;') Point is that I don't think Exporter will work for you if your
package name does not match your module filename.
The other option is the object-oriented interface, but please don't make
yet-another module with null objects just to use the inheritance
functionality.
A bit of reading to do:
perldoc -q "how do I create a module"
perldoc -q "How do I add a directory to my include path at runtime?"
perldoc lib
perldoc perlmod
perldoc perlobj
Basically, you have a tree like so:
lib/
|-- MyModule
| |-- Inline.pm
| `-- Pure.pm
`-- MyModule.pm
And these three files:
$cat lib/MyModule.pm
package MyModule;
BEGIN {
eval{require MyModule::Inline;};
if($@) {
warn "sorry, no Inline available\n";
require MyModule::Pure;
}
}
require Exporter;
@ISA='Exporter';
# note, maybe @EXPORT_OK instead (perldoc Exporter)
@EXPORT = qw (
add
);
1;
$cat lib/MyModule/Inline.pm
package MyModule;
use Inline C => <<'EOC';
long add (long a, long b) {
printf("adding in C\n");
return(a + b);
}
EOC
1;
$cat lib/MyModule/Pure.pm
package MyModule;
sub add {
print "adding in perl\n";
return($_[0] + $_[1]);
}
1;
Then you run this:
$perl -Ilib -e 'use MyModule;
print add(7, 9);'
and you get:
adding in C
16
This requires three modules, but gets Exporter to work. Also, you can define
always-perl functions in MyModule.pm. Only put the either/or functions in
the Inline.pm and Pure.pm files, since this setup gives you only one or the
other.
If you want, you could just do 'use MyModule::Pure' instead of the require, as
long as it happens in the BEGIN block *before* you do the require
MyModule::Inline (since you want the C functions to over-load the pure-perl
ones.)
--Eric
--
"These crispix get soggy so quickly."
-- Tina Connolly
