class PDF::Reader::Filter::RunLength

def filter(data)
  pos = 0
  out = "".dup
  while pos < data.length
    length = data.getbyte(pos)
    pos += 1
    unless length.nil?
      case
        # nothing
      when length == 128
        break
      when length < 128
        # When the length is < 128, we copy the following length+1 bytes
        # literally.
        out << data[pos, length + 1]
        pos += length
      else
        # When the length is > 128, we copy the next byte (257 - length)
        # times; i.e., "\xFA\x00" ([250, 0]) will expand to
        # "\x00\x00\x00\x00\x00\x00\x00".
        previous_byte = data[pos, 1] || ""
        out << previous_byte * (257 - length)
      end
    end
    pos += 1
  end
  Depredict.new(@options).filter(out)
end

def initialize(options = {})
  @options = options
end