Package akka.routing

Class 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 Description
      MurmurHash()  

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method 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 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​(java.lang.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 Detail

      • MurmurHash

        public MurmurHash()

    • Method Detail

      • 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​(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.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.