sample ruby 1.9 validate_encoding hacky implementation

gistfile1.rb

# Pass in a string, will raise an Encoding::InvalidByteSequenceError
# if it contains an invalid byte for it's encoding; otherwise
# returns an equivalent string.
#
# OR, like String#encode, pass in option `:invalid => :replace`
# to replace invalid bytes with a replacement string in the
# returned string.  Pass in the
# char you'd like with option `:replace`, or will, like String#encode
# use the unicode replacement char if it thinks it's a unicode encoding,
# else ascii '?'.
#
# in any case, method will raise, or return a new string
# that is #valid_encoding?
def validate_encoding(str, options = {})
  str.chars.collect do |c|
    if c.valid_encoding?
      c
    else
      unless options[:invalid] == :replace
        # it ought to be filled out with all the metadata
        # this exception usually has, but what a pain!
        # Why isn't ruby doing this for us?
        raise  Encoding::InvalidByteSequenceError.new
      else
        options[:replace] || (
         # surely there's a better way to tell if
         # an encoding is a 'Unicode encoding form'
         # than this? What's wrong with you ruby 1.9?
         str.encoding.name.start_with?('UTF') ?
            "\uFFFD" :
            "?" )
      end
    end
  end.join
end