
Data.BloomFilter.Hash  Portability  portable  Stability  unstable  Maintainer  Bryan O'Sullivan <bos@serpentine.com> 





Description 
Fast hashing of Haskell values. The hash functions used are Bob
Jenkins's public domain functions, which combine high performance
with excellent mixing properties. For more details, see
http://burtleburtle.net/bob/hash/.
In addition to the usual one input, one output hash functions,
this module provides multioutput hash functions, suitable for use
in applications that need multiple hashes, such as Bloom filtering.


Synopsis 




Basic hash functionality



 Methods   :: a  value to hash
 > Word32  salt
 > IO Word32   Compute a 32bit hash of a value. The salt value perturbs
the result.

   :: a  value to hash
 > Word64  salt
 > IO Word64   Compute a 64bit hash of a value. The first salt value
perturbs the first element of the result, and the second salt
perturbs the second.


  Instances  Hashable Bool  Hashable Char  Hashable Double  Hashable Float  Hashable Int  Hashable Int8  Hashable Int16  Hashable Int32  Hashable Int64  Hashable Integer  Hashable Ordering  Hashable Word8  Hashable Word16  Hashable Word32  Hashable Word64  Hashable ()  Hashable ByteString  Hashable ByteString  Storable a => Hashable [a]  Hashable a => Hashable (Maybe a)  (Hashable a, Hashable b) => Hashable (Either a b)  (Hashable a, Hashable b) => Hashable (a, b)  (Hashable a, Hashable b, Hashable c) => Hashable (a, b, c)  (Hashable a, Hashable b, Hashable c, Hashable d) => Hashable (a, b, c, d)  (Hashable a, Hashable b, Hashable c, Hashable d, Hashable e) => Hashable (a, b, c, d, e) 




Compute a 32bit hash.










Compute a family of hash values



:: Hashable a   => Int  number of hashes to compute
 > a  value to hash
 > [Word32]   Compute a list of 32bit hashes. The value to hash may be
inspected as many times as there are hashes requested.




:: Hashable a   => Int  number of hashes to compute
 > a  value to hash
 > [Word32]   Compute a list of 32bit hashes relatively cheaply. The value to
hash is inspected at most twice, regardless of the number of hashes
requested.
We use a variant of Kirsch and Mitzenmacher's technique from "Less
Hashing, Same Performance: Building a Better Bloom Filter",
http://www.eecs.harvard.edu/~kirsch/pubs/bbbf/esa06.pdf.
Where Kirsch and Mitzenmacher multiply the second hash by a
coefficient, we shift right by the coefficient. This offers better
performance (as a shift is much cheaper than a multiply), and the
low order bits of the final hash stay well mixed.



Hash functions for Storable instances



Compute a 32bit hash of a Storable instance.



Compute a 64bit hash of a Storable instance.



Compute a 32bit hash of a list of Storable instances.



Compute a 64bit hash of a list of Storable instances.


Produced by Haddock version 2.6.1 