Fast XML escaping in Ruby 1.9 using FFI/libxml2

gistfile1.rb

require 'ffi'

module XmlEscaper
  extend FFI::Library
  ffi_lib 'xml2'
  UTF8 = Encoding.find('UTF-8')

  def self.escape(string)
    char_ptr = self.xmlEncodeSpecialChars(nil, string)
    encoded = char_ptr.read_string
    encoded.force_encoding(UTF8)
    self.free(char_ptr)

    encoded
  end

protected

  # from xml2; returns char* that must be freed:
  attach_function :xmlEncodeSpecialChars, [:pointer, :string], :pointer

  # from libc:
  attach_function :free, [:pointer], :void
end

XmlEscaper.escape('test&ing')
# => "test&ing"