Postings by Mathias on November 15, 2007
Easy Publish and Consume Library
As GNOME remembers the meaning of the 'N' in its name, more and more GNOME applications become network aware. GNOME provides excellent libraries for implementing network capabilities, nevertheless quite some effort is needed to glue them together to provide a smooth user experience.
When starting to add network support to Glom, we at Openismus decided it would be time to stop this frequent reinvention of the wheel, and put some of this glue code into an easy to use library. So the Easy Publish and Consume Library (libepc) was born.
The Easy Publish and Consume Library is intended to provide an easy method to
- publish data per HTTPS
- announce that information via DNS-SD,
- find that information
- and finally consume it
When using that library you shall not bother about boring details like properly using Avahi or setting up SSL/TLS certificates. All you should do to let your application publish information to the network, is writing the following three commands:
publisher = epc_publisher_new ("Easy Publisher Example", NULL, NULL);
epc_publisher_add (publisher, "Hello", "World!", -1);
epc_publisher_run_async ();
Once you have done this, your application runs a HTTPS server, announcing itself to the local network via DNS-SD and publishes the information World! under the key Hello.
Retrieving values shouldn't be harder:
consumer = epc_consumer_new_for_name ("Easy Publisher Example");
value = epc_consumer_lookup (consumer, "Hello", &length, &error);
As those examples are working now, we Openismus guys would highly welcome some feedback - I even added e-mail notifications to my site to allow real discussion.
Well, maybe it should be noted, that libepc isn't meant to replace desktop configuration daemons like GConf or Ryan's dconf initiative. This library just is a simple method for publishing byte arrays and maybe UTF-8 strings to your network. No support for integers, booleans, no schemas. It's fully up to you, how to use the data published.
- Source code is available: git clone http://taschenorakel.de/git/libepc
- Alternatively you can get tarballs: libepc-0.2.tar.bz2 (Signature), git snapshots
- Maybe more important at this stage: The Reference Manual
- And code examples: list-resources.c, lookup-resource.c, simple-publisher.c, consumer-ui.c
This locations at taschenorakel.de are just temporary locations, if nobody disagrees I'd like to upload this library to the GNOME servers as soon as possible.
Linking to library.gnome.org
Recently the brave gtk-doc guys introduced a tool called gtkdoc-rebase, which updates external links in your API docs to point on the GNOME Library. The gtk-doc.make script has been updated to run gtkdoc-rebase on make dist. Unfortunatly all this pretty stuff doesn't work out of the box on Gutsy, as two premise have to be fulfilled to make this voodoo work:
- The
index.sgmlfiles in the gtk-doc folder must be uncompressed. The gtk-doc and Ubuntu guys currently argue regarding that topic. - Your uncompressed
index.sgmlfiles must contain an<ONLINE>tag pointing on the online docs.
Updating all the gtk-docs I've got would have been a boring task. So I wrote a little script which updates the uncompressed index files, when documentation exists in the GNOME Library:
Use it carefully, as it sends HEAD requests to library.gnome.org for every gtk-doc package not having that <ONLINE> tag yet.
Did I mention already, that this script processes uncompressed index files only? So call sudo gunzip /usr/share/gtk-doc/html/*/index.sgml.gz before using it.
