gov.sandia.cognition.hash

Class FNV1a32Hash

java.lang.Object

gov.sandia.cognition.util.AbstractCloneableSerializable

gov.sandia.cognition.hash.AbstractHashFunction

gov.sandia.cognition.hash.FNV1a32Hash

All Implemented Interfaces:

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

@PublicationReference(author="Wikipedia",title="Fowler\u2013Noll\u2013Vo hash function",type=WebPage,year=2011,url="http://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function") @PublicationReference(author="Landon Curt Noll",title="FNV-1a",type=WebPage,year=2011,url="http://isthe.com/chongo/tech/comp/fnv/#FNV-1a")
public class FNV1a32Hash
extends AbstractHashFunction

Implementation of the 32-bit (4-byte) Fowler-Noll-Vo (FNV-1a) hash function.

Since:

3.4.2

Author:

Kevin R. Dixon

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_PRIME Default FNV-1 prime, 16777619.
protected static byte[]	DEFAULT_SEED Byte representation of DEFAULT_SEED_INT
static int	DEFAULT_SEED_INT Default FNV-1 seed, -2128831035 == (signed) 2166136261
static int	LENGTH Length of the hash is 32-bits (4-bytes), 4.

Constructor Summary

Constructors

Constructor and Description
FNV1a32Hash() Creates a new instance of FNV1a32Hash

Method Summary

Modifier and Type	Method and Description
FNV1a32Hash	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 int	hash(byte[] input) FNV-1a 32-bit hash function
static int	hash(byte[] input, int seed) FNV-1a 32-bit hash function
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 is 32-bits (4-bytes), 4.

See Also:

Constant Field Values

DEFAULT_SEED_INT

public static final int DEFAULT_SEED_INT

Default FNV-1 seed, -2128831035 == (signed) 2166136261

See Also:

Constant Field Values

DEFAULT_SEED

protected static final byte[] DEFAULT_SEED

Byte representation of DEFAULT_SEED_INT

DEFAULT_PRIME

public static final int DEFAULT_PRIME

Default FNV-1 prime, 16777619.

See Also:

Constant Field Values

Constructor Detail

FNV1a32Hash

public FNV1a32Hash()

Creates a new instance of FNV1a32Hash

Method Detail

clone

public FNV1a32Hash 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

hash

public static int hash(byte[] input)

FNV-1a 32-bit hash function

Parameters:

input - Input to hash

Returns:

32-bit FNV-1a hash

hash

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

FNV-1a 32-bit hash function

Parameters:

input - Input to hash

seed - Seed to use as the offset

Returns:

32-bit FNV-1a hash

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.