+ tokyocabinet for "tc" DB adaptor
+ http://1978th.net/tokyocabinet/
+ you can install Ruby bindings via "gem install tokyocabinet",
+ but this still requires libtokyocabinet to be installed system-wide
+ bdb (berkeley db) for "bdb" DB adaptor or converting from it
+ http://raa.ruby-lang.org/project/bdb/