org.egothor.duplicity.util

Class Hasher

java.lang.Object

org.egothor.duplicity.util.Hasher

All Implemented Interfaces:

UIDProducer

public class Hasher
extends Object
implements UIDProducer

Simple implementation of interface UIDProducer. The UIDs are produced by hash function. The implementation is not perfect, in the sense that the provided mapping from tokens to UIDs is not surjective nor it does avoid collisions. For the collisions let's say that as we do not know the whole set of possible tokens, construction of perfect hash function is not possible. For the non-surjectivity of the mapping, I believe it is not a problem. Currently there are implementations of DJB and SDBM algorithms. The type of algorithm to be used must be declared on creating of the object of this class.

Author:

Kateřina Dufková

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT Constant for default hash algorith.
static int	DJB Constant for DJB hash algorith.
static int	SDBM Constant for SDBM hash algorith.

Constructor Summary

Constructors

Constructor and Description
Hasher(int type) Constructor sets the type of hash function to be used.

Method Summary

Modifier and Type	Method and Description
int	getType()
long	getUID(String str) Get the UID for given String value.

Methods inherited from class java.lang.Object

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

Field Detail

DJB

public static final int DJB

Constant for DJB hash algorith.

See Also:

Constant Field Values

SDBM

public static final int SDBM

Constant for SDBM hash algorith.

See Also:

Constant Field Values

DEFAULT

public static final int DEFAULT

Constant for default hash algorith.

See Also:

Constant Field Values

Constructor Detail

Hasher

public Hasher(int type)

Constructor sets the type of hash function to be used.

Parameters:

type - constant of the class Hasher

Method Detail

getType

public int getType()

getUID

public long getUID(String str)

Get the UID for given String value.

Specified by:

getUID in interface UIDProducer

Parameters:

str -

Returns:

UID