Package org.apache.datasketches.memory

Class MurmurHash3v2

java.lang.Object

org.apache.datasketches.memory.MurmurHash3v2

public final class MurmurHash3v2
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 Memory 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.

Author:

Lee Rhodes

Constructor Summary

Constructors

Constructor	Description
MurmurHash3v2()

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(String in, long seed, long[] hashOut)	Returns a 128-bit hash of the input.
static long[]	hash(Memory mem, long offsetBytes, long lengthBytes, long seed, long[] hashOut)	Returns a 128-bit hash of the input as a long array of size 2.

Methods inherited from class java.lang.Object

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

Constructor Detail

MurmurHash3v2

public MurmurHash3v2()

Method Detail

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

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

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

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

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

hash

public static long[] hash(Memory mem,
                          long offsetBytes,
                          long lengthBytes,
                          long seed,
                          long[] hashOut)

Returns a 128-bit hash of the input as a long array of size 2.

Parameters:

mem - The input on-heap Memory. Must be non-null and non-empty, otherwise throws IllegalArgumentException.

offsetBytes - the starting point within Memory.

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.