Added the Maskbits module and type.

diff --git a/src/Maskbits.hs b/src/Maskbits.hs
new file mode 100644 (file)
index 0000000..cb4ab89
--- /dev/null
+++ b/src/Maskbits.hs
@@ -0,0 +1,22 @@
+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)