class Crass::Tokenizer

def consume_escaped

4.3.8. http://dev.w3.org/csswg/css-syntax/#consume-an-escaped-code-point

or EOF.
next character in the input has already been verified not to be a newline
This method assumes that the `\` has already been consumed, and that the

Consumes an escaped code point and returns its unescaped value. 
def consume_escaped
  return "\ufffd" if @s.eos?
  if hex_str = @s.scan(RE_HEX)
    @s.consume if @s.peek =~ RE_WHITESPACE
    codepoint = hex_str.hex
    if codepoint == 0 ||
        codepoint.between?(0xD800, 0xDFFF) ||
        codepoint > 0x10FFFF
      return "\ufffd"
    else
      return codepoint.chr(Encoding::UTF_8)
    end
  end
  @s.consume
end