| Portability | portable |
|---|---|
| Stability | experimental |
| Maintainer | jcpetruzza@gmail.com |
| Safe Haskell | None |
Data.Hash.Rolling
Description
Efficient implementation of a rolling hash, i.e., the computation of a hash through
a moving window of a fixed size n over some stream. All operations are O(1) (in
particular, they do not depend on the size of the window).
Some laws that this type satisfies:
currentHash rh == foldl1 combine (lastHashes rh)
length (lastHashes rh) <= windowSize rh
length (lastHashes $ addAndRoll rh a) == windowSize rh -- whenever length (lastHashes rh) == windowSize rh
last (lastHashes $ addAndRoll rh x) == hash a
init (lastHashes $ addAndRoll rh a)
isSuffixOf(lastHashes rh)
- data RollingHash a
- rollingHash :: Int -> RollingHash a
- addAndRoll :: Hashable a => RollingHash a -> a -> RollingHash a
- currentHash :: RollingHash a -> Hash
- lastHashes :: RollingHash a -> [Hash]
- windowSize :: RollingHash a -> Int
The RollingHash type
data RollingHash a Source
Instances
| Show (RollingHash a) |
Construction and manipulation
rollingHash :: Int -> RollingHash aSource
rollingHash n creates a RollingHash of window
size n (for n > 0)
addAndRoll :: Hashable a => RollingHash a -> a -> RollingHash aSource
addAndRoll x rh adds a new input element and rolls the window
one place through the input (if at least n elements were
already consumed).
Querying
currentHash :: RollingHash a -> HashSource
lastHashes :: RollingHash a -> [Hash]Source
lastHashes rh returns the last n hashes.
windowSize :: RollingHash a -> IntSource