Class MurmurHash3FFM

java.lang.Object
org.apache.datasketches.hash.MurmurHash3FFM
public final class MurmurHash3FFM extends Object
The MurmurHash3 is a fast, non-cryptographic, 128-bit hash function that has excellent avalanche and 2-way bit independence properties.

Austin Appleby's C++ MurmurHash3_x64_128(...), final revision 150, which is in the Public Domain, was the inspiration for this implementation in Java.

This implementation of the MurmurHash3 allows hashing of a block of on-heap MemorySegment defined by an offset and length. The calling API also allows the user to supply the small output array of two longs, so that the entire hash function is static and free of object allocations.

This implementation produces exactly the same hash result as the MurmurHash3 function in datasketches-java given compatible inputs.

This FFM version of the implementation leverages the java.lang.foreign package (FFM) of JDK-25 in place of the Unsafe class.

Author:
Lee Rhodes

  • Method Summary

    Modifier and Type
    Method
    Description
    static long[]
    hash(byte[] in, long seed)
    Returns a 128-bit hash of the input.
    static long[]
    hash(char[] in, long seed)
    Returns a 128-bit hash of the input.
    static long[]
    hash(double in, long seed, long[] hashOut)
    Returns a 128-bit hash of the input.
    static long[]
    hash(int[] in, long seed)
    Returns a 128-bit hash of the input.
    static long[]
    hash(long[] in, long seed)
    Returns a 128-bit hash of the input.
    static long[]
    hash(long in, long seed, long[] hashOut)
    Returns a 128-bit hash of the input.
    static long[]
    hash(MemorySegment seg, long offsetBytes, long lengthBytes, long seed, long[] hashOut)
    Returns a 128-bit hash of the input as a long array of size 2.
    static long[]
    hash(String in, long seed, long[] hashOut)
    Returns a 128-bit hash of the input.

    Methods inherited from class Object

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

  • Method Details

    • hash

      public static long[] hash(long[] in, long seed)
      Returns a 128-bit hash of the input. Provided for compatibility with older version of MurmurHash3, but empty or null input now throws IllegalArgumentException.
      Parameters:
      in - long array
      seed - A long valued seed.
      Returns:
      the hash
      Throws:
      IllegalArgumentException - if input is empty or null

    • hash

      public static long[] hash(int[] in, long seed)
      Returns a 128-bit hash of the input. Provided for compatibility with older version of MurmurHash3, but empty or null input now throws IllegalArgumentException.
      Parameters:
      in - int array
      seed - A long valued seed.
      Returns:
      the hash
      Throws:
      IllegalArgumentException - if input is empty or null

    • hash

      public static long[] hash(char[] in, long seed)
      Returns a 128-bit hash of the input. Provided for compatibility with older version of MurmurHash3, but empty or null input now throws IllegalArgumentException.
      Parameters:
      in - char array
      seed - A long valued seed.
      Returns:
      the hash
      Throws:
      IllegalArgumentException - if input is empty or null

    • hash

      public static long[] hash(byte[] in, long seed)
      Returns a 128-bit hash of the input. Provided for compatibility with older version of MurmurHash3, but empty or null input now throws IllegalArgumentException.
      Parameters:
      in - byte array
      seed - A long valued seed.
      Returns:
      the hash
      Throws:
      IllegalArgumentException - if input is empty or null

    • hash

      public static long[] hash(long in, long seed, long[] hashOut)
      Returns a 128-bit hash of the input. Note the entropy of the resulting hash cannot be more than 64 bits.
      Parameters:
      in - a long
      seed - A long valued seed.
      hashOut - A long array of size 2
      Returns:
      the hash

    • hash

      public static long[] hash(double in, long seed, long[] hashOut)
      Returns a 128-bit hash of the input. Note the entropy of the resulting hash cannot be more than 64 bits.
      Parameters:
      in - a double
      seed - A long valued seed.
      hashOut - A long array of size 2
      Returns:
      the hash

    • hash

      public static long[] hash(String in, long seed, long[] hashOut)
      Returns a 128-bit hash of the input. An empty or null input throws IllegalArgumentException.
      Parameters:
      in - a String
      seed - A long valued seed.
      hashOut - A long array of size 2
      Returns:
      the hash
      Throws:
      IllegalArgumentException - if input is empty or null

    • hash

      public static long[] hash(MemorySegment seg, long offsetBytes, long lengthBytes, long seed, long[] hashOut)
      Returns a 128-bit hash of the input as a long array of size 2.
      Parameters:
      seg - The input MemorySegment. Must be non-null and non-empty, otherwise throws IllegalArgumentException.
      offsetBytes - the starting point within MemorySegment.
      lengthBytes - the total number of bytes to be hashed.
      seed - A long valued seed.
      hashOut - the size 2 long array for the resulting 128-bit hash
      Returns:
      the hash.
      Throws:
      IllegalArgumentException - if input MemorySegment is empty