X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FOctet.hs;h=04caae54fa6bcefab22d28415f5e2e8f6aa81064;hb=a767881c16a119a90ff80d9c14106348d8bc310d;hp=f8af4df8c90ec51f6db9bac93e92a1d1abc7c79f;hpb=6c076a2622dd9a6bfc96ed05f8478b5150db176a;p=hath.git

diff --git a/src/Octet.hs b/src/Octet.hs
index f8af4df..04caae5 100644
--- a/src/Octet.hs
+++ b/src/Octet.hs
@@ -1,19 +1,27 @@
 module Octet where
 
+import Test.HUnit
+
 import Bit
 
 -- An Octet consists of eight bits. For our purposes, the most
 -- significant bit will come "first." That is, b1 is in the 2^7
 -- place while b8 is in the 2^0 place.
-data Octet = Octet { b1 :: Bit,
-                     b2 :: Bit,
-                     b3 :: Bit,
-                     b4 :: Bit,
-                     b5 :: Bit,
-                     b6 :: Bit,
-                     b7 :: Bit,
-                     b8 :: Bit }
-           deriving (Eq, Show)
+data Octet = None | Octet { b1 :: Bit,
+                            b2 :: Bit,
+                            b3 :: Bit,
+                            b4 :: Bit,
+                            b5 :: Bit,
+                            b6 :: Bit,
+                            b7 :: Bit,
+                            b8 :: Bit }
+           deriving (Eq)
+
+
+instance Show Octet where
+    show Octet.None = "None"
+    show oct = show (octet_to_int oct)
+
 
 -- Convert each bit to its integer value, and multiply by the
 -- appropriate power of two. Sum them up, and we should get an integer
@@ -27,23 +35,30 @@ octet_to_int x =
     8   * (bit_to_int (b5 x)) +
     4   * (bit_to_int (b6 x)) +
     2   * (bit_to_int (b7 x)) +
-    0   * (bit_to_int (b8 x))
+    1   * (bit_to_int (b8 x))
+
 
 
--- Supply an integer greater than 255 at your own risk.
 octet_from_int :: Int -> Octet
 octet_from_int x
-    | (x < 0) = min_octet 
+    | (x < 0) || (x > 255) = Octet.None
     | otherwise = (Octet a1 a2 a3 a4 a5 a6 a7 a8)
     where
-      a1 = if (x `mod` 128) > 0 then One else Zero
-      a2 = if (x `mod` 64)  > 0 then One else Zero
-      a3 = if (x `mod` 32)  > 0 then One else Zero           
-      a4 = if (x `mod` 16)  > 0 then One else Zero
-      a5 = if (x `mod` 8)   > 0 then One else Zero
-      a6 = if (x `mod` 4)   > 0 then One else Zero
-      a7 = if (x `mod` 2)   > 0 then One else Zero           
-      a8 = if (x `mod` 1)   > 0 then One else Zero
+      a1 = if (x >= 128) then One else Zero
+      a2 = if ((x `mod` 128) >= 64) then One else Zero
+      a3 = if ((x `mod` 64)  >= 32) then One else Zero
+      a4 = if ((x `mod` 32)  >= 16) then One else Zero
+      a5 = if ((x `mod` 16)  >= 8)  then One else Zero
+      a6 = if ((x `mod` 8)   >= 4)  then One else Zero
+      a7 = if ((x `mod` 4)   >= 2)  then One else Zero
+      a8 = if ((x `mod` 2)   == 1)  then One else Zero
+
+
+octet_from_string :: String -> Octet
+octet_from_string s =
+    case (reads s :: [(Int, String)]) of
+      []   -> Octet.None
+      x:_ -> octet_from_int (fst x)
 
 
 -- The octet with the least possible value.
@@ -54,3 +69,16 @@ min_octet = Octet Zero Zero Zero Zero Zero Zero Zero Zero
 -- The octet with the greatest possible value.
 max_octet :: Octet
 max_octet = Octet One One One One One One One One
+
+
+
+-- HUnit Tests
+test_octet_from_int1 :: Test
+test_octet_from_int1 =
+    TestCase $ assertEqual "octet_from_int 128 should parse as 10000000" oct1 (octet_from_int 128)
+    where
+      oct1 = Octet One Zero Zero Zero Zero Zero Zero Zero
+
+
+octet_tests :: [Test]
+octet_tests = [ test_octet_from_int1 ]