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 )
-- | 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
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
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
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
projects / hath.git / blobdiff