class PDF::Reader::XRef

def load_xref_table
  tok_one = tok_two = nil
  begin
    # loop over all subsections of the xref table
    # In a well formed PDF, the 'trailer' token will indicate
    # the end of the table. However we need to be careful in case 
    # we're processing a malformed pdf that is missing the trailer.
    loop do
      tok_one, tok_two = @buffer.token, @buffer.token
      if tok_one != "trailer" && !tok_one.match(/\d+/)
        raise MalformedPDFError, "PDF malformed, missing trailer after cross reference"
      end
      break if tok_one == "trailer" or tok_one.nil?
      objid, count = tok_one.to_i, tok_two.to_i
      count.times do
        offset = @buffer.token.to_i
        generation = @buffer.token.to_i
        state = @buffer.token
        store(objid, generation, offset) if state == "n"
        objid += 1
      end
    end
  rescue EOFError => e
    raise MalformedPDFError, "PDF malformed, missing trailer after cross reference"
  end
  raise MalformedPDFError, "PDF malformed, trailer should be a dictionary" unless tok_two == "<<"
  trailer = Parser.new(@buffer, self).dictionary
  load(trailer['Prev'].to_i) if trailer.has_key?('Prev')
  trailer
end