org.tribuo.util

Class MurmurHash3

java.lang.Object

org.tribuo.util.MurmurHash3

public final class MurmurHash3
extends Object

The MurmurHash3 algorithm was created by Austin Appleby and placed in the public domain. This java port was authored by Yonik Seeley and also placed into the public domain. The author hereby disclaims copyright to this source code.

This produces exactly the same hash values as the final C++ version of MurmurHash3 and is thus suitable for producing the same hash values across platforms.

The 32 bit x86 version of this hash should be the fastest variant for relatively short keys like ids. murmurhash3_x64_128 is a good choice for longer strings or if you need more than 32 bits of hash.

Note - The x86 and x64 versions do _not_ produce the same results, as the algorithms are optimized for their respective platforms.

See http://github.com/yonik/java_util for future updates to this file.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	MurmurHash3.LongPair 128 bits of state

Constructor Summary

Constructors

Constructor and Description
MurmurHash3()

Method Summary

Modifier and Type	Method and Description
static int	fmix32(int h)
static long	fmix64(long k)
static long	getLongLittleEndian(byte[] buf, int offset) Gets a long from a byte buffer in little endian byte order.
static void	murmurhash3_x64_128(byte[] key, int offset, int len, int seed, MurmurHash3.LongPair out) Returns the MurmurHash3_x64_128 hash, placing the result in "out".
static int	murmurhash3_x86_32(byte[] data, int offset, int len, int seed) Returns the MurmurHash3_x86_32 hash.
static int	murmurhash3_x86_32(CharSequence data, int offset, int len, int seed) Returns the MurmurHash3_x86_32 hash of the UTF-8 bytes of the String without actually encoding the string to a temporary buffer.

Methods inherited from class java.lang.Object

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

Constructor Detail

MurmurHash3

public MurmurHash3()

Method Detail

fmix32

public static final int fmix32(int h)

fmix64

public static final long fmix64(long k)

getLongLittleEndian

public static final long getLongLittleEndian(byte[] buf,
                                             int offset)

Gets a long from a byte buffer in little endian byte order.

Parameters:

buf - The buffer to operate on.

offset - The current offset into the buffer.

Returns:

A long.

murmurhash3_x86_32

public static int murmurhash3_x86_32(byte[] data,
                                     int offset,
                                     int len,
                                     int seed)

Returns the MurmurHash3_x86_32 hash.

Parameters:

data - The data to hash.

offset - The offset into the data.

len - The length of the data to hash.

seed - The initial seed of the hash.

Returns:

The murmurhash3_x86_32 hash.

murmurhash3_x86_32

public static int murmurhash3_x86_32(CharSequence data,
                                     int offset,
                                     int len,
                                     int seed)

Returns the MurmurHash3_x86_32 hash of the UTF-8 bytes of the String without actually encoding the string to a temporary buffer. This is more than 2x faster than hashing the result of String.getBytes().

Parameters:

data - The data to hash.

offset - The offset into the data.

len - The length of the data to hash.

seed - The initial seed of the hash.

Returns:

The murmurhash3_x86_32 hash.

murmurhash3_x64_128

public static void murmurhash3_x64_128(byte[] key,
                                       int offset,
                                       int len,
                                       int seed,
                                       MurmurHash3.LongPair out)

Returns the MurmurHash3_x64_128 hash, placing the result in "out".

Parameters:

key - The data to hash.

offset - The offset into the data.

len - The length of the data to hash.

seed - The initial state of the hash.

out - The output value (as it's 128 bits).