src/Octet.hs

   1 module Octet where
   2
   3 import Test.HUnit
   4 import Test.QuickCheck
   5
   6 import Bit as B
   7 import Maskable
   8 import Maskbits
   9
  10 -- An Octet consists of eight bits. For our purposes, the most
  11 -- significant bit will come "first." That is, b1 is in the 2^7
  12 -- place while b8 is in the 2^0 place.
  13 data Octet = None | Octet { b1 :: Bit,
  14                             b2 :: Bit,
  15                             b3 :: Bit,
  16                             b4 :: Bit,
  17                             b5 :: Bit,
  18                             b6 :: Bit,
  19                             b7 :: Bit,
  20                             b8 :: Bit }
  21            deriving (Eq)
  22
  23
  24 instance Show Octet where
  25     show Octet.None = "None"
  26     show oct = show (octet_to_int oct)
  27
  28
  29 instance Arbitrary Octet where
  30     arbitrary = do
  31       a1 <- arbitrary :: Gen Bit
  32       a2 <- arbitrary :: Gen Bit
  33       a3 <- arbitrary :: Gen Bit
  34       a4 <- arbitrary :: Gen Bit
  35       a5 <- arbitrary :: Gen Bit
  36       a6 <- arbitrary :: Gen Bit
  37       a7 <- arbitrary :: Gen Bit
  38       a8 <- arbitrary :: Gen Bit
  39       return (Octet a1 a2 a3 a4 a5 a6 a7 a8)
  40
  41     coarbitrary _ = variant 0
  42
  43
  44 instance Maskable Octet where
  45     apply_mask _ Maskbits.None = Octet.None
  46     apply_mask Octet.None _    = Octet.None
  47     apply_mask oct mask
  48         | mask == Eight = oct
  49         | mask == Seven = oct { b8 = B.Zero }
  50         | mask == Six = oct { b8 = B.Zero, b7 = B.Zero }
  51         | mask == Five = oct { b8 = B.Zero, b7 = B.Zero, b6 = B.Zero }
  52         | mask == Four = oct { b8 = B.Zero, b7 = B.Zero, b6 = B.Zero, b5 = B.Zero }
  53         | mask == Three = oct { b8 = B.Zero, b7 = B.Zero, b6 = B.Zero, b5 = B.Zero, b4 = B.Zero }
  54         | mask == Two = oct { b8 = B.Zero, b7 = B.Zero, b6 = B.Zero, b5 = B.Zero, b4 = B.Zero, b3 = B.Zero }
  55         | mask == Maskbits.One = oct { b8 = B.Zero, b7 = B.Zero, b6 = B.Zero, b5 = B.Zero, b4 = B.Zero, b3 = B.Zero, b2 = B.Zero }
  56         | mask == Maskbits.Zero = min_octet
  57         | otherwise = Octet.None
  58
  59
  60 -- Convert each bit to its integer value, and multiply by the
  61 -- appropriate power of two. Sum them up, and we should get an integer
  62 -- between 0 and 255.
  63 octet_to_int :: Octet -> Int
  64 octet_to_int x =
  65     128 * (bit_to_int (b1 x)) +
  66     64  * (bit_to_int (b2 x)) +
  67     32  * (bit_to_int (b3 x)) +
  68     16  * (bit_to_int (b4 x)) +
  69     8   * (bit_to_int (b5 x)) +
  70     4   * (bit_to_int (b6 x)) +
  71     2   * (bit_to_int (b7 x)) +
  72     1   * (bit_to_int (b8 x))
  73
  74
  75
  76 octet_from_int :: Int -> Octet
  77 octet_from_int x
  78     | (x < 0) || (x > 255) = Octet.None
  79     | otherwise = (Octet a1 a2 a3 a4 a5 a6 a7 a8)
  80     where
  81       a1 = if (x >= 128) then B.One else B.Zero
  82       a2 = if ((x `mod` 128) >= 64) then B.One else B.Zero
  83       a3 = if ((x `mod` 64)  >= 32) then B.One else B.Zero
  84       a4 = if ((x `mod` 32)  >= 16) then B.One else B.Zero
  85       a5 = if ((x `mod` 16)  >= 8)  then B.One else B.Zero
  86       a6 = if ((x `mod` 8)   >= 4)  then B.One else B.Zero
  87       a7 = if ((x `mod` 4)   >= 2)  then B.One else B.Zero
  88       a8 = if ((x `mod` 2)   == 1)  then B.One else B.Zero
  89
  90
  91 octet_from_string :: String -> Octet
  92 octet_from_string s =
  93     case (reads s :: [(Int, String)]) of
  94       []   -> Octet.None
  95       x:_ -> octet_from_int (fst x)
  96
  97
  98 -- The octet with the least possible value.
  99 min_octet :: Octet
 100 min_octet = Octet B.Zero B.Zero B.Zero B.Zero B.Zero B.Zero B.Zero B.Zero
 101
 102
 103 -- The octet with the greatest possible value.
 104 max_octet :: Octet
 105 max_octet = Octet B.One B.One B.One B.One B.One B.One B.One B.One
 106
 107
 108
 109 -- HUnit Tests
 110 test_octet_from_int1 :: Test
 111 test_octet_from_int1 =
 112     TestCase $ assertEqual "octet_from_int 128 should parse as 10000000" oct1 (octet_from_int 128)
 113     where
 114       oct1 = Octet B.One B.Zero B.Zero B.Zero B.Zero B.Zero B.Zero B.Zero
 115
 116
 117 test_octet_mask1 :: Test
 118 test_octet_mask1 =
 119     TestCase $ assertEqual "The network bits of 255/4 should equal 240" oct2 (apply_mask oct1 Four)
 120     where
 121       oct1 = octet_from_int 255
 122       oct2 = octet_from_int 240
 123
 124
 125 test_octet_mask2 :: Test
 126 test_octet_mask2 =
 127     TestCase $ assertEqual "The network bits of 255/1 should equal 128" oct2 (apply_mask oct1 Maskbits.One)
 128     where
 129       oct1 = octet_from_int 255
 130       oct2 = octet_from_int 128
 131
 132
 133 octet_tests :: [Test]
 134 octet_tests = [ test_octet_from_int1,
 135                 test_octet_mask1,
 136                 test_octet_mask2 ]