in6_addr

# File lib/ipaddr.rb, line 457
  def in6_addr(left)
    case left
    when /^::ffff:(\d+\.\d+\.\d+\.\d+)$/i
      return in_addr($1) + 0xffff00000000
    when /^::(\d+\.\d+\.\d+\.\d+)$/i
      return in_addr($1)
    when /[^0-9a-f:]/i
      raise ArgumentError, "invalid address"
    when /^(.*)::(.*)$/
      left, right = $1, $2
    else
      right = ''
    end
    l = left.split(':')
    r = right.split(':')
    rest = 8 - l.size - r.size
    if rest < 0
      return nil
    end
    a = [l, Array.new(rest, '0'), r].flatten!
    n = 0
    a.each { |i|
      n <<= 16
      n += i.hex
    }
    return n
  end