io.milton.zsync

Class Rsum

java.lang.Object

io.milton.zsync.Rsum

All Implemented Interfaces:

RollingChecksum, Serializable, Cloneable

public class Rsum
extends Object
implements RollingChecksum, Cloneable, Serializable

Implementation of rolling checksum for zsync purposes

Author:

Tomáš Hlavnička

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
Rsum() Constructor of rolling checksum

Method Summary

Modifier and Type	Method and Description
void	check(byte[] buf, int offset, int length) Update the checksum with an entirely different block, and potentially a different block length.
Object	clone() Copies this checksum instance into a new instance.
boolean	equals(Object o) Tests if a particular checksum is equal to this checksum.
void	first(byte[] buf, int offset, int length) Update the checksum with an entirely different block, and potentially a different block length.
int	getValue() Return the value of the currently computed checksum.
void	reset() Reset the checksum
void	roll(byte newByte) Rolling checksum that takes single byte and compute checksum of block from file in offset that equals offset of newByte minus length of block

Methods inherited from class java.lang.Object

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

Constructor Detail

Rsum

public Rsum()

Constructor of rolling checksum

Method Detail

getValue

public int getValue()

Return the value of the currently computed checksum.

Specified by:

getValue in interface RollingChecksum

Returns:

The currently computed checksum.

reset

public void reset()

Reset the checksum

Specified by:

reset in interface RollingChecksum

roll

public void roll(byte newByte)

Rolling checksum that takes single byte and compute checksum of block from file in offset that equals offset of newByte minus length of block

Specified by:

roll in interface RollingChecksum

Parameters:

newByte - New byte that will actualize a checksum

check

public void check(byte[] buf,
                  int offset,
                  int length)

Update the checksum with an entirely different block, and potentially a different block length.

Specified by:

check in interface RollingChecksum

Parameters:

buf - The byte array that holds the new block.

offset - From whence to begin reading.

length - The length of the block to read.

first

public void first(byte[] buf,
                  int offset,
                  int length)

Update the checksum with an entirely different block, and potentially a different block length. This method is only used to initialize rolling checksum.

Specified by:

first in interface RollingChecksum

Parameters:

buf - The byte array that holds the new block.

offset - From whence to begin reading.

length - The length of the block to read.

clone

public Object clone()

Description copied from interface: RollingChecksum

Copies this checksum instance into a new instance. This method should be optional, and only implemented if the class implements the Cloneable interface.

Specified by:

clone in interface RollingChecksum

Overrides:

clone in class Object

Returns:

A clone of this instance.

equals

public boolean equals(Object o)

Description copied from interface: RollingChecksum

Tests if a particular checksum is equal to this checksum. This means that the other object is an instance of this class, and its internal state equals this checksum's internal state.

Specified by:

equals in interface RollingChecksum

Overrides:

equals in class Object

Parameters:

o - The object to test.

Returns:

true if this checksum equals the other checksum.