Motivation

(Warning: boring story ahead. Skip to next section if you want.)

Quite a while ago, I thought it would be kind of nice if my Ruby MUD server would run on JRuby, since JRuby might be better at dealing with long-running server processes. Unfortunately, at the time, EventMachine did not have a Java version, so I decided to wait for that to work.

A while later, there was some kind of Java release for EventMachine. I tried it out, but then ran into another problem: gdbm is provided as a C extension for the standard Ruby distribution. So, I gave up again.

Then, along came Ruby FFI and I thought, “Hm…wonder if I could use that…” and then I gave up because I am not very good at C, even just trying to read it.

THEN, I saw this blog post about the next version of JRuby (1.4) and decided maybe I should do something about it, after all. So I did.

ffi-gdbm

The result is a gdbm library which should be fully compatible with the standard C extension distributed with Ruby, including reading and writing gdbm files which can be read/written by either implementation.

Requirements

Although I had hoped to make this library compatible with any Ruby FFI implementation, unfortunately it only works with JRuby, and it needs at least version 1.4. Perhaps this will change as the other Ruby FFI implementations get fancier.

Installation

You can checkout ffi-gdbm on GitHub. All you actually need is the gdbm.rb file.

Alternatively, you can install it as a gem:

jgem install gdbm --source http://gemcutter.org

Make sure you require "rubygems" if you do use the gem version.

Usage

You can use this library just as you would the standard library that comes with Ruby. See here for documentation.

Aftermath

Unfortunately, the Java version of EventMachine is still incomplete, so it’s a bit of letdown, although kams does work at least nominally using it. Hopefully, EventMachine will one day be completely stable under JRuby.