src/Maskbits.hs

   1 module Maskbits
   2 ( Maskbits(..),
   3   maskbits_from_string
   4 ) where
   5
   6 -- A type representing the number of bits in a CIDR netmask.
   7 data Maskbits = None | Maskbits Int
   8               deriving (Eq, Show)
   9
  10
  11 -- There are only 32 bits in an IPv4 address, so there
  12 -- can't be more bits than that in the mask.
  13 maskbits_from_int :: Int -> Maskbits
  14 maskbits_from_int x | (x < 0) || (x > 32) = None
  15                     | otherwise = Maskbits x
  16
  17
  18 maskbits_from_string :: String -> Maskbits
  19 maskbits_from_string s =
  20     case (reads s :: [(Int, String)]) of
  21       []   -> None
  22       x:_ -> maskbits_from_int (fst x)