Package org.apache.pekko.routing

Class MurmurHash

java.lang.Object
org.apache.pekko.routing.MurmurHash
public class MurmurHash extends 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
    Description
    MurmurHash()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    static <T> int
    arrayHash(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
    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
    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(String s)
    Compute a high-quality hash of a string
    static <T> int
    symmetricHash(scala.collection.IterableOnce<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 Details

    • MurmurHash

      public MurmurHash()

  • Method Details

    • 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
      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(Object a)
      Compute a high-quality hash of an array

    • stringHash

      public static int stringHash(String s)
      Compute a high-quality hash of a string

    • symmetricHash

      public static <T> int symmetricHash(scala.collection.IterableOnce<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.