module Maskbits
( Maskbits(..),
  maskbits_from_string
) where

-- A type representing the number of bits in a CIDR netmask.
data Maskbits = None | Maskbits Int
              deriving (Eq, Show)


-- There are only 32 bits in an IPv4 address, so there
-- can't be more bits than that in the mask.
maskbits_from_int :: Int -> Maskbits
maskbits_from_int x | (x < 0) || (x > 32) = None
                    | otherwise = Maskbits x


maskbits_from_string :: String -> Maskbits
maskbits_from_string s =
    case (reads s :: [(Int, String)]) of
      []   -> None
      x:_ -> maskbits_from_int (fst x)