akka.routing

Class MurmurHash

java.lang.Object

akka.routing.MurmurHash

public class MurmurHash
extends java.lang.Object

An object designed to generate well-distributed non-cryptographic hashes. It is designed to hash a collection of integers; along with the integers to hash, it generates two magic streams of integers to increase the distribution of repetitive input sequences. Thus, three methods need to be called at each step (to start and to incorporate a new integer) to update the values. Only one method needs to be called to finalize the hash.

Constructor Summary

Constructors

Constructor and Description
MurmurHash()

Method Summary

Modifier and Type	Method and Description
static <T> int	arrayHash(java.lang.Object a) Compute a high-quality hash of an array
static int	extendHash(int hash, int value, int magicA, int magicB) Incorporates a new value into an existing hash.
static int	finalizeHash(int hash) Once all hashes have been incorporated, this performs a final mixing
static int	hiddenMagicA()
static int	hiddenMagicB()
static int	nextMagicA(int magicA) Given a magic integer from the first stream, compute the next
static int	nextMagicB(int magicB) Given a magic integer from the second stream, compute the next
static int	seedArray()
static int	startHash(int seed) Begin a new hash with a seed value.
static int	startMagicA() The initial magic integers in the first stream.
static int	startMagicB() The initial magic integer in the second stream.
static int	stringHash(java.lang.String s) Compute a high-quality hash of a string
static <T> int	symmetricHash(scala.collection.TraversableOnce<T> xs, int seed) Compute a hash that is symmetric in its arguments--that is, where the order of appearance of elements does not matter.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

MurmurHash

public MurmurHash()

Method Detail

hiddenMagicA

public static final int hiddenMagicA()

hiddenMagicB

public static final int hiddenMagicB()

seedArray

public static final int seedArray()

startHash

public static int startHash(int seed)

Begin a new hash with a seed value.

startMagicA

public static int startMagicA()

The initial magic integers in the first stream.

startMagicB

public static int startMagicB()

The initial magic integer in the second stream.

extendHash

public static int extendHash(int hash,
                             int value,
                             int magicA,
                             int magicB)

Incorporates a new value into an existing hash.

Parameters:

hash - the prior hash value

value - the new value to incorporate

magicA - a magic integer from the stream

magicB - a magic integer from a different stream

hash - (undocumented)

value - (undocumented)

Returns:

the updated hash value

nextMagicA

public static int nextMagicA(int magicA)

Given a magic integer from the first stream, compute the next

nextMagicB

public static int nextMagicB(int magicB)

Given a magic integer from the second stream, compute the next

finalizeHash

public static int finalizeHash(int hash)

Once all hashes have been incorporated, this performs a final mixing

arrayHash

public static <T> int arrayHash(java.lang.Object a)

Compute a high-quality hash of an array

stringHash

public static int stringHash(java.lang.String s)

Compute a high-quality hash of a string

symmetricHash

public static <T> int symmetricHash(scala.collection.TraversableOnce<T> xs,
                                    int seed)

Compute a hash that is symmetric in its arguments--that is, where the order of appearance of elements does not matter. This is useful for hashing sets, for example.

Parameters:

xs - (undocumented)

seed - (undocumented)

Returns:

(undocumented)