7 -- An Octet consists of eight bits. For our purposes, the most
8 -- significant bit will come "first." That is, b1 is in the 2^7
9 -- place while b8 is in the 2^0 place.
10 data Octet = None | Octet { b1 :: Bit,
21 instance Show Octet where
22 show Octet.None = "None"
23 show oct = show (octet_to_int oct)
26 -- Convert each bit to its integer value, and multiply by the
27 -- appropriate power of two. Sum them up, and we should get an integer
29 octet_to_int :: Octet -> Int
31 128 * (bit_to_int (b1 x)) +
32 64 * (bit_to_int (b2 x)) +
33 32 * (bit_to_int (b3 x)) +
34 16 * (bit_to_int (b4 x)) +
35 8 * (bit_to_int (b5 x)) +
36 4 * (bit_to_int (b6 x)) +
37 2 * (bit_to_int (b7 x)) +
38 1 * (bit_to_int (b8 x))
42 octet_from_int :: Int -> Octet
44 | (x < 0) || (x > 255) = Octet.None
45 | otherwise = (Octet a1 a2 a3 a4 a5 a6 a7 a8)
47 a1 = if (x >= 128) then One else Zero
48 a2 = if ((x `mod` 128) >= 64) then One else Zero
49 a3 = if ((x `mod` 64) >= 32) then One else Zero
50 a4 = if ((x `mod` 32) >= 16) then One else Zero
51 a5 = if ((x `mod` 16) >= 8) then One else Zero
52 a6 = if ((x `mod` 8) >= 4) then One else Zero
53 a7 = if ((x `mod` 4) >= 2) then One else Zero
54 a8 = if ((x `mod` 2) == 1) then One else Zero
57 octet_from_string :: String -> Octet
59 case (reads s :: [(Int, String)]) of
61 x:_ -> octet_from_int (fst x)
64 -- The octet with the least possible value.
66 min_octet = Octet Zero Zero Zero Zero Zero Zero Zero Zero
69 -- The octet with the greatest possible value.
71 max_octet = Octet One One One One One One One One
76 test_octet_from_int1 :: Test
77 test_octet_from_int1 =
78 TestCase $ assertEqual "octet_from_int 128 should parse as 10000000" oct1 (octet_from_int 128)
80 oct1 = Octet One Zero Zero Zero Zero Zero Zero Zero
84 octet_tests = [ test_octet_from_int1 ]