UUIDv7 in Ruby, using IO::Buffer

uuid_v7.rb

def uuid_v7
  milliseconds = Process.clock_gettime(Process::CLOCK_REALTIME, :millisecond)
  buffer = IO::Buffer.new(16)
  buffer.set_string([milliseconds].pack('Q>')[2..], 0)
  buffer.set_string(SecureRandom.bytes(10), 6)
  buffer.set_value(:U8, 6, buffer.get_value(:U8, 6) & 0x0F | 0x70)
  buffer.set_value(:U8, 8, buffer.get_value(:U8, 8) & 0x3F | 0x80)

  buffer.get_string.unpack('H8H4H4H4H12').join('-')
end