fast_xs provides C extensions for escaping text.

The original String#fast_xs method is based on the xchar code by Sam Ruby:

o   intertwingly.net/stories/2005/09/28/xchar.rb
o   intertwingly.net/blog/2005/09/28/XML-Cleansing

_why also packages an older version with Hpricot (patches submitted). The
version here should be compatible with the latest version of Hpricot code.

Ruby on Rails will automatically use String#fast_xs from either Hpricot or this
gem version with the bundled Builder package.

String#fast_xs is an almost exact translation of Sam Ruby's original
implementation (String#to_xs), but it does escape """ (which is an
optional, but all parsers are able ot handle it. XML::Builder as packaged in
Rails 2.0 will be automatically use String#fast_xs instead of String#to_xs
available.