Package org.apache.commons.codec.digest

Class MurmurHash3

java.lang.Object

org.apache.commons.codec.digest.MurmurHash3

public final class MurmurHash3
extends java.lang.Object

MurmurHash3 yields a 32-bit or 128-bit value. MurmurHash is a non-cryptographic hash function suitable for general hash-based lookup. The name comes from two basic operations, multiply (MU) and rotate (R), used in its inner loop. Unlike cryptographic hash functions, it is not specifically designed to be difficult to reverse by an adversary, making it unsuitable for cryptographic purposes. 32-bit Java port of https://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp#94 128-bit Java port of https://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp#255 This is a public domain code with no copyrights. From homepage of MurmurHash (https://code.google.com/p/smhasher/), "All MurmurHash versions are public domain software, and the author disclaims all copyright to their code." Copied from Apache Hive: https://github.com/apache/hive/blob/master/storage-api/src/java/org/apache/hive/common/util/Murmur3.java

Since:

1.13

See Also:

MurmurHash

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	MurmurHash3.IncrementalHash32

Field Summary

Fields

Modifier and Type	Field	Description
private static long	C1
private static int	C1_32
private static long	C2
private static int	C2_32
static int	DEFAULT_SEED
(package private) static int	INTEGER_BYTES	TODO Replace on Java 8 with Integer.BYTES.
(package private) static int	LONG_BYTES	TODO Replace on Java 8 with Long.BYTES.
private static int	M
private static int	M_32
private static int	N_32
private static int	N1
private static int	N2
static long	NULL_HASHCODE
private static int	R1
private static int	R1_32
private static int	R2
private static int	R2_32
private static int	R3
(package private) static int	SHORT_BYTES	TODO Replace on Java 8 with Short.BYTES.

Constructor Summary

Constructors

Modifier	Constructor	Description
private	MurmurHash3()

Method Summary

Modifier and Type	Method	Description
private static int	fmix32(int length, int hash)
private static long	fmix64(long h)
static long[]	hash128(byte[] data)	Murmur3 128-bit variant.
static long[]	hash128(byte[] data, int offset, int length, int seed)	Murmur3 128-bit variant.
static long[]	hash128(java.lang.String data)	Murmur3 128-bit variant.
static int	hash32(byte[] data)	Generates 32 bit hash from byte array with the default seed.
static int	hash32(byte[] data, int length)	Generates 32 bit hash from byte array with the default seed.
static int	hash32(byte[] data, int length, int seed)	Generates 32 bit hash from byte array with the given length and seed.
static int	hash32(byte[] data, int offset, int length, int seed)	Generates 32 bit hash from byte array with the given length, offset and seed.
static int	hash32(long l0)	Generates 32 bit hash from a long with default seed value.
static int	hash32(long l0, int seed)	Generates 32 bit hash from a long with the given seed.
static int	hash32(long l0, long l1)	Generates 32 bit hash from two longs with default seed value.
static int	hash32(long l0, long l1, int seed)	Generates 32 bit hash from two longs with the given seed.
static int	hash32(java.lang.String data)	Generates 32 bit hash from a string with the default seed.
static long	hash64(byte[] data)	Murmur3 64-bit variant.
static long	hash64(byte[] data, int offset, int length)	Generates 64 bit hash from byte array with the given length, offset and default seed.
static long	hash64(byte[] data, int offset, int length, int seed)	Generates 64 bit hash from byte array with the given length, offset and seed.
static long	hash64(int data)	Murmur3 64-bit variant.
static long	hash64(long data)	Murmur3 64-bit variant.
static long	hash64(short data)	Murmur3 64-bit variant.
private static int	mix32(int k, int hash)
private static int	orBytes(byte b1, byte b2, byte b3, byte b4)

Methods inherited from class java.lang.Object

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

Field Detail

LONG_BYTES

static final int LONG_BYTES

TODO Replace on Java 8 with Long.BYTES.

See Also:

Constant Field Values

INTEGER_BYTES

static final int INTEGER_BYTES

TODO Replace on Java 8 with Integer.BYTES.

See Also:

Constant Field Values

SHORT_BYTES

static final int SHORT_BYTES

TODO Replace on Java 8 with Short.BYTES.

See Also:

Constant Field Values

NULL_HASHCODE

public static final long NULL_HASHCODE

See Also:

Constant Field Values

C1_32

private static final int C1_32

See Also:

Constant Field Values

C2_32

private static final int C2_32

See Also:

Constant Field Values

R1_32

private static final int R1_32

See Also:

Constant Field Values

R2_32

private static final int R2_32

See Also:

Constant Field Values

M_32

private static final int M_32

See Also:

Constant Field Values

N_32

private static final int N_32

See Also:

Constant Field Values

C1

private static final long C1

See Also:

Constant Field Values

C2

private static final long C2

See Also:

Constant Field Values

R1

private static final int R1

See Also:

Constant Field Values

R2

private static final int R2

See Also:

Constant Field Values

R3

private static final int R3

See Also:

Constant Field Values

M

private static final int M

See Also:

Constant Field Values

N1

private static final int N1

See Also:

Constant Field Values

N2

private static final int N2

See Also:

Constant Field Values

DEFAULT_SEED

public static final int DEFAULT_SEED

See Also:

Constant Field Values

Constructor Detail

MurmurHash3

private MurmurHash3()

Method Detail

hash32

public static int hash32(long l0,
                         long l1)

Generates 32 bit hash from two longs with default seed value.

Parameters:

l0 - long to hash

l1 - long to hash

Returns:

32 bit hash

hash32

public static int hash32(long l0)

Generates 32 bit hash from a long with default seed value.

Parameters:

l0 - long to hash

Returns:

32 bit hash

hash32

public static int hash32(long l0,
                         int seed)

Generates 32 bit hash from a long with the given seed.

Parameters:

l0 - long to hash

seed - initial seed value

Returns:

32 bit hash

hash32

public static int hash32(long l0,
                         long l1,
                         int seed)

Generates 32 bit hash from two longs with the given seed.

Parameters:

l0 - long to hash

l1 - long to hash

seed - initial seed value

Returns:

32 bit hash

hash32

public static int hash32(byte[] data)

Generates 32 bit hash from byte array with the default seed.

Parameters:

data - - input byte array

Returns:

32 bit hash

hash32

public static int hash32(java.lang.String data)

Generates 32 bit hash from a string with the default seed.

Parameters:

data - - input string

Returns:

32 bit hash

hash32

public static int hash32(byte[] data,
                         int length)

Generates 32 bit hash from byte array with the default seed.

Parameters:

data - - input byte array

length - - length of array

Returns:

32 bit hash

hash32

public static int hash32(byte[] data,
                         int length,
                         int seed)

Generates 32 bit hash from byte array with the given length and seed.

Parameters:

data - - input byte array

length - - length of array

seed - - seed. (default 0)

Returns:

32 bit hash

hash32

public static int hash32(byte[] data,
                         int offset,
                         int length,
                         int seed)

Generates 32 bit hash from byte array with the given length, offset and seed.

Parameters:

data - - input byte array

offset - - offset of data

length - - length of array

seed - - seed. (default 0)

Returns:

32 bit hash

hash64

public static long hash64(byte[] data)

Murmur3 64-bit variant. This is essentially MSB 8 bytes of Murmur3 128-bit variant.

Parameters:

data - - input byte array

Returns:

64 bit hash

hash64

public static long hash64(long data)

Murmur3 64-bit variant. This is essentially MSB 8 bytes of Murmur3 128-bit variant.

Parameters:

data - - input long

Returns:

64 bit hash

hash64

public static long hash64(int data)

Murmur3 64-bit variant. This is essentially MSB 8 bytes of Murmur3 128-bit variant.

Parameters:

data - - input int

Returns:

64 bit hash

hash64

public static long hash64(short data)

Murmur3 64-bit variant. This is essentially MSB 8 bytes of Murmur3 128-bit variant.

Parameters:

data - - input short

Returns:

64 bit hash

hash64

public static long hash64(byte[] data,
                          int offset,
                          int length)

Generates 64 bit hash from byte array with the given length, offset and default seed.

Parameters:

data - - input byte array

offset - - offset of data

length - - length of array

Returns:

64 bit hash

hash64

public static long hash64(byte[] data,
                          int offset,
                          int length,
                          int seed)

Generates 64 bit hash from byte array with the given length, offset and seed.

Parameters:

data - - input byte array

offset - - offset of data

length - - length of array

seed - - seed. (default 0)

Returns:

64 bit hash

hash128

public static long[] hash128(byte[] data)

Murmur3 128-bit variant.

Parameters:

data - - input byte array

Returns:

- 128 bit hash (2 longs)

hash128

public static long[] hash128(java.lang.String data)

Murmur3 128-bit variant.

Parameters:

data - - input String

Returns:

- 128 bit hash (2 longs)

hash128

public static long[] hash128(byte[] data,
                             int offset,
                             int length,
                             int seed)

Murmur3 128-bit variant.

Parameters:

data - - input byte array

offset - - the first element of array

length - - length of array

seed - - seed. (default is 0)

Returns:

- 128 bit hash (2 longs)

mix32

private static int mix32(int k,
                         int hash)

fmix32

private static int fmix32(int length,
                          int hash)

fmix64

private static long fmix64(long h)

orBytes

private static int orBytes(byte b1,
                           byte b2,
                           byte b3,
                           byte b4)