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
  42 instance Maskable Octet where
  43     apply_mask _ Maskbits.None _ = Octet.None
  44     apply_mask Octet.None _ _    = Octet.None
  45     apply_mask oct mask bit
  46         | mask == Eight = oct
  47         | mask == Seven = oct { b8 = bit }
  48         | mask == Six = oct { b8 = bit, b7 = bit }
  49         | mask == Five = oct { b8 = bit, b7 = bit, b6 = bit }
  50         | mask == Four = oct { b8 = bit, b7 = bit, b6 = bit, b5 = bit }
  51         | mask == Three = oct { b8 = bit, b7 = bit, b6 = bit, b5 = bit, b4 = bit }
  52         | mask == Two = oct { b8 = bit, b7 = bit, b6 = bit, b5 = bit, b4 = bit, b3 = bit }
  53         | mask == Maskbits.One = oct { b8 = bit, b7 = bit, b6 = bit, b5 = bit, b4 = bit, b3 = bit, b2 = bit }
  54         | mask == Maskbits.Zero = oct { b8 = bit, b7 = bit, b6 = bit, b5 = bit, b4 = bit, b3 = bit, b2 = bit, b1 = bit }
  55         | otherwise = Octet.None
  56
  57
  58 -- Convert each bit to its integer value, and multiply by the
  59 -- appropriate power of two. Sum them up, and we should get an integer
  60 -- between 0 and 255.
  61 octet_to_int :: Octet -> Int
  62 octet_to_int x =
  63     128 * (bit_to_int (b1 x)) +
  64     64  * (bit_to_int (b2 x)) +
  65     32  * (bit_to_int (b3 x)) +
  66     16  * (bit_to_int (b4 x)) +
  67     8   * (bit_to_int (b5 x)) +
  68     4   * (bit_to_int (b6 x)) +
  69     2   * (bit_to_int (b7 x)) +
  70     1   * (bit_to_int (b8 x))
  71
  72
  73
  74 octet_from_int :: Int -> Octet
  75 octet_from_int x
  76     | (x < 0) || (x > 255) = Octet.None
  77     | otherwise = (Octet a1 a2 a3 a4 a5 a6 a7 a8)
  78     where
  79       a1 = if (x >= 128) then B.One else B.Zero
  80       a2 = if ((x `mod` 128) >= 64) then B.One else B.Zero
  81       a3 = if ((x `mod` 64)  >= 32) then B.One else B.Zero
  82       a4 = if ((x `mod` 32)  >= 16) then B.One else B.Zero
  83       a5 = if ((x `mod` 16)  >= 8)  then B.One else B.Zero
  84       a6 = if ((x `mod` 8)   >= 4)  then B.One else B.Zero
  85       a7 = if ((x `mod` 4)   >= 2)  then B.One else B.Zero
  86       a8 = if ((x `mod` 2)   == 1)  then B.One else B.Zero
  87
  88
  89 octet_from_string :: String -> Octet
  90 octet_from_string s =
  91     case (reads s :: [(Int, String)]) of
  92       []   -> Octet.None
  93       x:_ -> octet_from_int (fst x)
  94
  95
  96 -- The octet with the least possible value.
  97 min_octet :: Octet
  98 min_octet = Octet B.Zero B.Zero B.Zero B.Zero B.Zero B.Zero B.Zero B.Zero
  99
 100
 101 -- The octet with the greatest possible value.
 102 max_octet :: Octet
 103 max_octet = Octet B.One B.One B.One B.One B.One B.One B.One B.One
 104
 105
 106
 107 -- HUnit Tests
 108 test_octet_from_int1 :: Test
 109 test_octet_from_int1 =
 110     TestCase $ assertEqual "octet_from_int 128 should parse as 10000000" oct1 (octet_from_int 128)
 111     where
 112       oct1 = Octet B.One B.Zero B.Zero B.Zero B.Zero B.Zero B.Zero B.Zero
 113
 114
 115 test_octet_mask1 :: Test
 116 test_octet_mask1 =
 117     TestCase $ assertEqual "The network bits of 255/4 should equal 240" oct2 (apply_mask oct1 Four B.Zero)
 118     where
 119       oct1 = octet_from_int 255
 120       oct2 = octet_from_int 240
 121
 122
 123 test_octet_mask2 :: Test
 124 test_octet_mask2 =
 125     TestCase $ assertEqual "The network bits of 255/1 should equal 128" oct2 (apply_mask oct1 Maskbits.One B.Zero)
 126     where
 127       oct1 = octet_from_int 255
 128       oct2 = octet_from_int 128
 129
 130
 131 octet_tests :: [Test]
 132 octet_tests = [ test_octet_from_int1,
 133                 test_octet_mask1,
 134                 test_octet_mask2 ]