X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FIPv4Address.hs;h=38aec8dd39c5250279a05357db753c8aa2247cf2;hb=HEAD;hp=80a499ec88f66e1907471ea7e0fb2af10ac9d5c3;hpb=8a3ca8823d4e8b8adbf3060ec056aafaf9813ded;p=hath.git diff --git a/src/IPv4Address.hs b/src/IPv4Address.hs index 80a499e..f9fd8c2 100644 --- a/src/IPv4Address.hs +++ b/src/IPv4Address.hs @@ -5,13 +5,17 @@ module IPv4Address( most_sig_bit_different ) where +import Data.Int ( Int32, Int64 ) +import Data.Word ( Word32 ) import Test.Tasty ( TestTree, testGroup ) import Test.Tasty.HUnit ( (@?=), testCase ) import Test.Tasty.QuickCheck ( Arbitrary( arbitrary ), Gen, + Large, Property, + Small, (==>), testProperty ) @@ -188,18 +192,26 @@ instance Enum IPv4Address where -- | Convert an 'Int' @x@ to an 'IPv4Address'. Each octet of @x@ is -- right-shifted by the appropriate number of bits, and the fractional -- part is dropped. - toEnum x = + toEnum signed_x = IPv4Address oct1 oct2 oct3 oct4 where + -- Convert the input Int to a Word32 before we proceed. On x86, + -- the Int that we get could be negative (half of all IP + -- addresses correspond to negative numbers), and then the magic + -- below doesn't work. The Word32 type is unsigned, so we do the + -- math on that and then convert everything back to Int later on + -- once we have four much-smaller non-negative numbers. + x = fromIntegral signed_x :: Word32 + -- Chop off the higher octets. x1 = x `mod` 2^32, would be -- redundant. - x2 = x `mod` 2^(24 :: Integer) - x3 = x `mod` 2^(16 :: Integer) - x4 = x `mod` 2^(8 :: Integer) + x2 = x `mod` (2 ^ (24 :: Integer)) + x3 = x `mod` (2 ^ (16 :: Integer)) + x4 = (fromIntegral $ x `mod` (2 ^ (8 :: Integer))) :: Int -- Perform right-shifts. x4 doesn't need a shift. - shifted_x1 = x `quot` 2^(24 :: Integer) - shifted_x2 = x2 `quot` 2^(16 :: Integer) - shifted_x3 = x3 `quot` 2^(8 :: Integer) + shifted_x1 = (fromIntegral $ x `quot` (2 ^ (24 :: Integer))) :: Int + shifted_x2 = (fromIntegral $ x2 `quot` (2 ^ (16 :: Integer))) :: Int + shifted_x3 = (fromIntegral $ x3 `quot` (2 ^ (8 :: Integer))) :: Int oct1 = toEnum shifted_x1 :: Octet oct2 = toEnum shifted_x2 :: Octet oct3 = toEnum shifted_x3 :: Octet @@ -214,9 +226,9 @@ instance Enum IPv4Address where oct2 = fromEnum (octet2 addr) oct3 = fromEnum (octet3 addr) oct4 = fromEnum (octet4 addr) - shifted_oct1 = oct1 * 2^(24 :: Integer) - shifted_oct2 = oct2 * 2^(16 :: Integer) - shifted_oct3 = oct3 * 2^(8 :: Integer) + shifted_oct1 = oct1 * (2 ^ (24 :: Integer)) + shifted_oct2 = oct2 * (2 ^ (16 :: Integer)) + shifted_oct3 = oct3 * (2 ^ (8 :: Integer)) -- | Given two addresses, find the number of the most significant bit -- where they differ. If the addresses are the same, return @@ -341,23 +353,52 @@ ipv4address_tests = test_minBound, test_most_sig_bit_different1, test_most_sig_bit_different2, + test_ord_instance1, + test_ord_instance2, + test_ord_instance3, + test_ord_instance4, test_to_enum ] ipv4address_properties :: TestTree ipv4address_properties = testGroup "IPv4 Address Properties " - [ prop_from_enum_to_enum_inverses ] + [ prop_from_enum_to_enum_inverses_x32, + prop_from_enum_to_enum_inverses_x64 ] -- QuickCheck properties -prop_from_enum_to_enum_inverses :: TestTree -prop_from_enum_to_enum_inverses = - testProperty "fromEnum and toEnum are inverses" prop +-- +-- We have two different tests to show that toEnum and fromEnum are +-- inverses of one another. This part of the code isn't really +-- type-safe, because the stupid Enum class insists that we use a +-- machine 'Int' for our representation. Since IPv4 addresses can +-- correspond to very large 32-bit integers, there's a possibility +-- that our math is wrong in 32- but not 64-bits, and vice-versa. +-- +-- tl;dr we want to ensure that this test passes when the 'Int' type +-- is both 32-bit and 64-bit. + +-- Generate "Small" 64-bit numbers, because almost all 64-bit integers are +-- too large to satisfy our predicate (i.e. also be 32-bit integers). +prop_from_enum_to_enum_inverses_x64 :: TestTree +prop_from_enum_to_enum_inverses_x64 = + testProperty "fromEnum and toEnum are inverses (x64)" prop + where + prop :: (Small Int64) -> Property + prop x = + 0 <= x && x <= (2 ^ (32 :: Integer)) - 1 ==> + fromIntegral (fromEnum (toEnum (fromIntegral x) :: IPv4Address)) == x + +-- According to the QuickCheck documentation, we need the "Large" +-- modifier to ensure that the test cases are drawn from the entire +-- range of Int32 values. +prop_from_enum_to_enum_inverses_x32 :: TestTree +prop_from_enum_to_enum_inverses_x32 = + testProperty "fromEnum and toEnum are inverses (x32)" prop where - prop :: Int -> Property + prop :: (Large Int32) -> Bool prop x = - (0 <= x) && (x <= 2^(32 :: Integer) - 1) ==> - fromEnum (toEnum x :: IPv4Address) == x + fromIntegral (fromEnum (toEnum (fromIntegral x) :: IPv4Address)) == x -- HUnit Tests mk_testaddr :: Int -> Int -> Int -> Int -> IPv4Address @@ -428,4 +469,50 @@ test_to_enum = where desc = "192.168.0.0 in base-10 is 3232235520" expected = mk_testaddr 192 168 0 0 - actual = toEnum 3232235520 :: IPv4Address + -- We declare the big number as Word32 because otherwise, on x86, + -- we get a warning that it's too big to fit in a 32-bit integer. + -- Ultimately we convert it to a (negative) Int on those systems + -- anyway, but the gymnastics declare our intent to the compiler. + actual = toEnum (fromIntegral (3232235520 :: Word32)) :: IPv4Address + + +test_ord_instance1 :: TestTree +test_ord_instance1 = + testCase desc $ actual @?= expected + where + desc = "127.0.0.0 is less than 127.0.0.1" + addr1 = mk_testaddr 127 0 0 0 + addr2 = mk_testaddr 127 0 0 1 + expected = True + actual = addr1 <= addr2 + + +test_ord_instance2 :: TestTree +test_ord_instance2 = + testCase desc $ actual @?= expected + where + desc = "127.0.0.0 is less than 127.0.1.0" + addr1 = mk_testaddr 127 0 0 0 + addr2 = mk_testaddr 127 0 1 0 + expected = True + actual = addr1 <= addr2 + +test_ord_instance3 :: TestTree +test_ord_instance3 = + testCase desc $ actual @?= expected + where + desc = "127.0.0.0 is less than 127.1.0.0" + addr1 = mk_testaddr 127 0 0 0 + addr2 = mk_testaddr 127 1 0 0 + expected = True + actual = addr1 <= addr2 + +test_ord_instance4 :: TestTree +test_ord_instance4 = + testCase desc $ actual @?= expected + where + desc = "127.0.0.0 is less than 128.0.0.0" + addr1 = mk_testaddr 127 0 0 0 + addr2 = mk_testaddr 128 0 0 0 + expected = True + actual = addr1 <= addr2