Data.LargeHashable.Class

This module defines the central type class LargeHashable of this package.

Documentation

class LargeHashable a where

A type class for computing hashes (i.e. MD5, SHA256, ...) from haskell values.

The laws of this typeclass are the following:

1. If two values are equal according to ==, then the finally computed hashes must also be equal according to ==. However it is not required that the hashes of inequal values have to be inequal. Also note that an instance of LargeHashable does not require a instance of Eq. Using any sane algorithm the chance of a collision should be 1 / n where n is the number of different hashes possible.
2. If two values are inequal according to ==, then the probability of a hash collision is 1/n, where n is the number of possible hashes produced by the underlying hash algorithm.

A rule of thumb: hash all information that you would also need for serializing/deserializing values of your datatype. For instance, when hashing lists, you would not only hash the list elements but also the length of the list. Consider the following datatype

data Foo = Foo [Int] [Int]

We now write an instance for LargeHashable like this

instance LargeHashable Foo where
    updateHash (Foo l1 l2) = updateHash l1 >> updateHash l2

If we did not hash the length of a list, then the following two values of Foo would produce identical hashes:

Foo [1,2,3] []
Foo [1] [2,3]

Minimal complete definition

Nothing

Methods

updateHash :: a -> LH ()

Instances

LargeHashable Bool

LargeHashable Char

LargeHashable Double

LargeHashable Float

LargeHashable Int

LargeHashable Int8

LargeHashable Int16

LargeHashable Int32

LargeHashable Int64

LargeHashable Integer

LargeHashable Ordering

LargeHashable Word

LargeHashable Word8

LargeHashable Word16

LargeHashable Word32

LargeHashable Word64

LargeHashable ()

LargeHashable ByteString

LargeHashable Scientific

LargeHashable ByteString

LargeHashable Text

LargeHashable UTCTime

LargeHashable Value

LargeHashable Text

LargeHashable Void

LargeHashable CChar

LargeHashable CUChar

LargeHashable CShort

LargeHashable CUShort

LargeHashable CInt

LargeHashable CUInt

LargeHashable CLong

LargeHashable CULong

LargeHashable ShortByteString

LargeHashable IntSet

LargeHashable AbsoluteTime

LargeHashable LocalTime

LargeHashable ZonedTime

LargeHashable TimeOfDay

LargeHashable TimeZone

LargeHashable NominalDiffTime

LargeHashable Day

LargeHashable UniversalTime

LargeHashable DiffTime

LargeHashable a => LargeHashable [a]

(Integral a, LargeHashable a) => LargeHashable (Ratio a)

LargeHashable a => LargeHashable (Maybe a)

HasResolution a => LargeHashable (Fixed a)

LargeHashable a => LargeHashable (IntMap a)

LargeHashable a => LargeHashable (Set a)

LargeHashable a => LargeHashable (Seq a)

LargeHashable a => LargeHashable (HashSet a)

LargeHashable a => LargeHashable (Vector a)

(LargeHashable a, LargeHashable b) => LargeHashable (Either a b)

(LargeHashable a, LargeHashable b) => LargeHashable (a, b)

(LargeHashable k, LargeHashable v) => LargeHashable (HashMap k v)

(LargeHashable k, LargeHashable a) => LargeHashable (Map k a)

(LargeHashable a, LargeHashable b) => LargeHashable (Pair a b)

(LargeHashable a, LargeHashable b, LargeHashable c) => LargeHashable (a, b, c)

(LargeHashable a, LargeHashable b, LargeHashable c, LargeHashable d) => LargeHashable (a, b, c, d)

(LargeHashable a, LargeHashable b, LargeHashable c, LargeHashable d, LargeHashable e) => LargeHashable (a, b, c, d, e)

largeHash :: LargeHashable a => HashAlgorithm h -> a -> h

largeHash is the central function of this package. For a given value it computes a Hash using the given HashAlgorithm.

class LargeHashable' t where

Methods

updateHash' :: LargeHashable a => t a -> LH ()