Using CSV files as a data source in an adapter is fairly simple. Ruby actually has first-class CSV file support:
There are several other csv parsers which claim to be faster, so you might want to take a look at some of these options: http://blog.grayproductions.net/articles/no_longer_the_fastest_game_in_town
Just make sure whichever 3rd-party gem you use (unless you use the built-in CSV ruby support), you add an entry in the Gemfile so it is loaded:
Then run "bundle install" to install it.