org.metastatic.rsync
Class MatcherStream

java.lang.Object
  |
  +--org.metastatic.rsync.MatcherStream

public class MatcherStream

extends Object

A streaming version of Matcher. The idea here is that the hashtable search is the most expensive operation in the rsync algorithm, and it is at times undesirable to wait for this to finish while whoever on the other end of the wire is waiting for our data. With this construction, we can send Deltas as soon as they are generated.

To implement the outgoing stream of Deltas, this class makes use of a callback interface, MatcherListener. Pass a concrete implementation of this interface to the addListener(MatcherListener) method, and a List of ChecksumPairs before calling any of the update methods. Once the data have been passed to these methods, call doFinal() to finish the process.

Field Summary

protected byte[]	buffer The intermediate byte buffer.
protected Configuration	config The configuration.
protected long	count The number of bytes summed thusfar.
protected TwoKeyMap	hashtable The current hashtable.
protected List	listeners The list of MatcherListeners.
protected int	ndx The current index in buffer.

Constructor Summary

MatcherStream(Configuration config)
Create a new MatcherStream.

Method Summary

void	addListener(MatcherListener listener) Add a MatcherListener to the list of listeners.
void	doFinal() Flush any buffered data and reset this instance.
protected Long	hashSearch(byte[] block, int off, int len) Search if a portion of the given byte array is in the map, returning its original offset if it is.
boolean	removeListener(MatcherListener listener) Remove a MatcherListener from the list of listeners.
void	reset() Reset this matcher, to be used for another data set.
void	setChecksums(List sums) Set the list of checksums that will be searched by this matcher.
void	update(byte b) Update this matcher with a single byte.
void	update(byte[] buf) Update this matcher with a byte array.
void	update(byte[] buf, int off, int len) Update this matcher with a portion of a byte array.

Methods inherited from class java.lang.Object

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

Field Detail

config

protected final Configuration config

The configuration.

listeners

protected final List listeners

The list of MatcherListeners.

hashtable

protected final TwoKeyMap hashtable

The current hashtable.

buffer

protected final byte[] buffer

The intermediate byte buffer.

ndx

protected int ndx

The current index in buffer.

count

protected long count

The number of bytes summed thusfar.

Constructor Detail

MatcherStream

public MatcherStream(Configuration config)

Create a new MatcherStream.

Parameters:

config - The current configuration.

Method Detail

addListener

public void addListener(MatcherListener listener)

Add a MatcherListener to the list of listeners.

Parameters:

listener - The listener to add.

removeListener

public boolean removeListener(MatcherListener listener)

Remove a MatcherListener from the list of listeners.

Parameters:

listener - The listener to add.

Returns:

True if a listener was really removed (i.e. that the listener was in the list to begin with).

setChecksums

public void setChecksums(List sums)

Set the list of checksums that will be searched by this matcher. This method must be called at least once before calling update.

Parameters:

sums - The checksums.

reset

public void reset()

Reset this matcher, to be used for another data set.

update

public void update(byte b)
            throws ListenerException

Update this matcher with a single byte.

Parameters:

b - The next byte

ListenerException

update

public void update(byte[] buf,
                   int off,
                   int len)
            throws ListenerException

Update this matcher with a portion of a byte array.

Parameters:

buf - The next bytes.

off - The offset to begin at.

len - The number of bytes to update.

ListenerException

update

public void update(byte[] buf)
            throws ListenerException

Update this matcher with a byte array.

Parameters:

buf - The next bytes.

ListenerException

doFinal

public void doFinal()
             throws ListenerException

Flush any buffered data and reset this instance.

ListenerException

hashSearch

protected Long hashSearch(byte[] block,
                          int off,
                          int len)

Search if a portion of the given byte array is in the map, returning its original offset if it is.

Parameters:

block - The block of bytes to search for.

off - The offset in the block to begin.

len - The number of bytes to read from the block.

Returns:

The original offset of the given block if it was found in the map. null if it was not found.