module HexDump

def self.regex_quote_n(raw)
  Regexp.quote(raw)
end

def self.regex_quote_n(raw)
  Regexp.quote(raw, 'n')
end

def encode(str)
  offset = 0
  result = []
  while raw = str.slice(offset, 16) and raw.length > 0
    # data field
    data = ''.dup
    for v in raw.unpack('N* a*')
      if v.kind_of? Integer
        data << sprintf("%08x ", v)
      else
        v.each_byte {|c| data << sprintf("%02x", c) }
      end
    end
    # text field
    text = raw.tr("\000-\037\177-\377", ".")
    result << sprintf("%08x  %-36s  %s", offset, data, text)
    offset += 16
    # omit duplicate line
    if /^(#{regex_quote_n(raw)})+/n =~ str[offset .. -1]
      result << sprintf("%08x  ...", offset)
      offset += $&.length
      # should print at the end
      if offset == str.length
        result << sprintf("%08x  %-36s  %s", offset-16, data, text)
      end
    end
  end
  result
end