gov.sandia.cognition.hash

Class Eva64Hash

java.lang.Object

gov.sandia.cognition.util.AbstractCloneableSerializable

gov.sandia.cognition.hash.AbstractHashFunction

gov.sandia.cognition.hash.Eva64Hash

All Implemented Interfaces:

Evaluator<byte[],byte[]>, HashFunction, CloneableSerializable, java.io.Serializable, java.lang.Cloneable

@PublicationReference(author="Robert J. Jenkins, Jr.",
                      title="Hash Functions for Hash Table Lookup",
                      type=WebPage,
                      year=1997,
                      url="http://burtleburtle.net/bob/hash/evahash.html")
public class Eva64Hash
extends AbstractHashFunction

This implements the 64-bit "evahash" due to Robert Jenkins. This is a Java port of Jenkins's C implementation.

Since:

3.4.2

Author:

Kevin R. Dixon

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected static byte[]	DEFAULT_SEED Default seed: ( 0, 0, 0, 0, 0, 0, 0, 0 ).
static int	LENGTH Length of the hash in bytes, 8.

Constructor Summary

Constructors

Constructor and Description
Eva64Hash() Creates a new instance of Eva64Hash

Method Summary

Modifier and Type	Method and Description
Eva64Hash	clone() This makes public the clone method on the Object class and removes the exception that it throws.
void	evaluateInto(byte[] input, byte[] output, byte[] seed) Evaluates the input into the given output
byte[]	getDefaultSeed() Gets the default seed for the hash function
static long	hash(byte[] input, long seed) Computes the Eva64Hash of the given input and the seed
int	length() Returns the number of bytes in the output hash code.

Methods inherited from class gov.sandia.cognition.hash.AbstractHashFunction

evaluate, evaluate, evaluateInto

Methods inherited from class java.lang.Object

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

Field Detail

LENGTH

public static final int LENGTH

Length of the hash in bytes, 8.

See Also:

Constant Field Values

DEFAULT_SEED

protected static final byte[] DEFAULT_SEED

Default seed: ( 0, 0, 0, 0, 0, 0, 0, 0 ).

Constructor Detail

Eva64Hash

public Eva64Hash()

Creates a new instance of Eva64Hash

Method Detail

clone

public Eva64Hash clone()

Description copied from class: AbstractCloneableSerializable

This makes public the clone method on the Object class and removes the exception that it throws. Its default behavior is to automatically create a clone of the exact type of object that the clone is called on and to copy all primitives but to keep all references, which means it is a shallow copy. Extensions of this class may want to override this method (but call super.clone() to implement a "smart copy". That is, to target the most common use case for creating a copy of the object. Because of the default behavior being a shallow copy, extending classes only need to handle fields that need to have a deeper copy (or those that need to be reset). Some of the methods in ObjectUtil may be helpful in implementing a custom clone method. Note: The contract of this method is that you must use super.clone() as the basis for your implementation.

Specified by:

clone in interface CloneableSerializable

Overrides:

clone in class AbstractHashFunction

Returns:

A clone of this object.

length

public int length()

Description copied from interface: HashFunction

Returns the number of bytes in the output hash code.

Returns:

Number of bytes in the output hash code.

getDefaultSeed

public byte[] getDefaultSeed()

Description copied from interface: HashFunction

Gets the default seed for the hash function

Returns:

Default seed for the hash algorithm

evaluateInto

public void evaluateInto(byte[] input,
                         byte[] output,
                         byte[] seed)

Description copied from interface: HashFunction

Evaluates the input into the given output

Parameters:

input - Input to compute the hash-function value of

output - Output to put the hash-function into

seed - Seed to offset the hash code.

hash

public static long hash(byte[] input,
                        long seed)

Computes the Eva64Hash of the given input and the seed

Parameters:

input - Input to consider

seed - Seed to offset the hash

Returns:

long representing the 64-bit hash function