From: Jason Roelofs <jameskilton@...>
Date: 2008-02-13T10:06:09+09:00
Subject: Re: Help Understanding Ruby/C Bindings

On Feb 12, 2008 7:32 PM, Bryan Richardson <btrichardson@gmail.com> wrote:
> Hello all,
>
> Can anyone walk me through how, for example, the binding between
> libpcap-ruby and libpcap?  If I look at pcaplet and pcap_misc, I notice
> that 'pcap' is required.  Is this another Ruby file (that I can't find)
> or is this referencing the libpcap C library directly?
>
> If anyone can explain to me how this works I'd greatly appreciate it.
> There's a good chance I'll need to be binding to C code from Ruby in the
> near future and I'd like to understand the best way to go about doing
> so.
>
> --
> Thanks!
> Bryan
> --
> Posted via http://www.ruby-forum.com/.
>
>

Kernel#require can load both another Ruby file or a Ruby extension.
Ruby extensions are shared libraries that are required to have at
least one certain method in them:

extension.c

void Init_extension() {
   ... initialization code here ...
}

builds into extension.so (on Linux, extension.dll on Windows)

Then you can

require 'extension'

and start using whatever the library has made available. In the case
of libpcap-ruby, there's a pcap.so file somewhere in your system (I'm
assuming you apt-get installed it, or the related on your system)
that's accessible by Ruby.

That's the gist of it, for more detailed information, go here:
http://www.rubycentral.com/pickaxe/ext_ruby.html

Jason