Convert Oracle's RAW(16) type to a GUID w/Ruby 2

raw_to_guid.rb

def is_guid?(guid)
  standard_guid = /([A-F\d]{8})-([A-F\d]{4})-([A-F\d]{4})-([A-F\d]{4})-([A-F\d]{12})/i
  (guid =~ standard_guid)
end

def to_byte_array(hex)
  hex.unpack('H*').first.scan(/[A-F\d]{4}/i)
end

def format_guid(string)
  guid_format = /([A-F\d]{8})([A-F\d]{4})([A-F\d]{4})([A-F\d]{4})([A-F\d]{12})/i
  string.scan(guid_format).join('-').downcase
end

def raw_to_guid(raw)
  # byte orders are flipped due to Endianness
  oracle_raw_idx = [3, 2, 1, 0, 5, 4, 7, 6, 8, 9, 10, 11, 12, 13, 14, 15]

  hex_bytes = to_byte_array(raw)
  hex_guid = oracle_raw_idx.map { |i| hex_bytes[i] }
  format_guid(hex_guid.join.split('!').pack('H*'))
end