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{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE UnboxedTuples #-}
module Data.Word64Map where
import Data.Bits
import qualified Data.IntMap as IntMap
;import Data.IntMap (IntMap)
import Data.Typeable
import Data.Word
-- | Since 'Int' may be 32 or 64 bits, this function is provided as a
-- convenience to test if an integral type, such as 'Data.Word.Word64', can be
-- safely transformed into an 'Int' for use with 'IntMap'.
--
-- Returns 'True' if the proxied type can be losslessly converted to 'Int' using
-- 'fromIntegral'.
fitsInInt :: forall proxy word. (Bounded word, Integral word) => proxy word -> Bool
fitsInInt proxy = (original == casted)
where
original = div maxBound 2 :: word
casted = fromIntegral (fromIntegral original :: Int) :: word
newtype Word64Map a = Word64Map (IntMap (IntMap a))
empty :: Word64Map a
empty = Word64Map IntMap.empty
-- Warning: This function assumes an 'Int' is either 64 or 32 bits.
keyFrom64 :: Word64 -> (# Int,Int #)
keyFrom64 w8 =
if fitsInInt (Proxy :: Proxy Word64)
then (# fromIntegral w8 , 0 #)
else (# fromIntegral (w8 `shiftR` 32), fromIntegral w8 #)
{-# INLINE keyFrom64 #-}
lookup :: Word64 -> Word64Map b -> Maybe b
lookup w8 (Word64Map m) | (# hi,lo #) <- keyFrom64 w8 = do
m' <- IntMap.lookup hi m
IntMap.lookup lo m'
{-# INLINE lookup #-}
insert :: Word64 -> b -> Word64Map b -> Word64Map b
insert w8 b (Word64Map m) | (# hi,lo #) <- keyFrom64 w8
= Word64Map $ IntMap.alter (Just . maybe (IntMap.singleton lo b)
(IntMap.insert lo b))
hi
m
{-# INLINE insert #-}
delete :: Word64 -> Word64Map b -> Word64Map b
delete w8 (Word64Map m) | (# hi,lo #) <- keyFrom64 w8
= Word64Map $ IntMap.alter (maybe Nothing
(\m' -> case IntMap.delete lo m' of
m'' | IntMap.null m'' -> Nothing
m'' -> Just m''))
hi
m
{-# INLINE delete #-}
|
