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java.net
Class Connector  

java.lang.Object
  java.net.Connector

All Implemented Interfaces:

java.lang.Runnable

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public class Connector

extends java.lang.Object

implements java.lang.Runnable

This class manage the compression layer for the stream (connected) scenario. It's a thread responsible for packet receiving and handling. It can guess if the packet is compressed and so should be decompressed or if it's an ack for a previously sent packet and should be used to compute statistics.

Version:

1.0

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Field Summary
protected  Compressor	compressor           Reference to the real compression engine that must follow the Compressor interface.
protected  Decompressor	decompressor           Reference to the real decompression engine that must follow the Decompressor interface.
protected  java.io.InputStream	in           Reference to the real input stream as provided by the plain-old socket factory, tipically PlainSocketImpl.
protected  Interpolator	interpolator           Reference to the real statistical modeler that must follow the Interpolator interface.
protected  java.util.Hashtable	listeners           List of objects waiting for ack.
protected  java.lang.Thread	myself
protected  boolean	notStop           This variable drive the main loop: a false value will stop the thread and prepare for exit.
protected  java.io.OutputStream	out           Reference to the real output stream as provided by the plain-old socket factory, tipically PlainSocketImpl.
protected  ZInputStream	zin           This input stream represents the input to the compression engine.
protected  ZOutputStream	zout           This output stream represents the output coming from the compression engine.

 

Constructor Summary

Connector(java.io.InputStream in, java.io.OutputStream out)           This constructor is used when the connector is not yet started and it is request by the method getInputStream 55 of our socket implementation.

Connector(java.io.OutputStream out, java.io.InputStream in)           See the previous constructor keeping in mind this one works for getOutputStream 55

 

Method Summary
protected  byte[]	compress(byte[] buf)           This method is responsible for data compression.
protected  void	create()           This internal method is the common part of constructors.
protected  byte[]	decompress(byte[] buf)           This method is responsible for data decompression.
java.io.InputStream	getInputStream()
java.io.OutputStream	getOutputStream()
void	run()           The main loop.
void	send(byte[] data)           This method is invoked by the ZoutputStream.flush 55 method to perform the real data sending.
void	sendAck(ZObject zobj)           An ack is sent through this method, based on the passed ZObject that's the received one.
void	stop()

 

Methods inherited from class java.lang.Object

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

 

Field Detail

compressor

protected Compressor compressor

Reference to the real compression engine that must follow the Compressor interface.

See Also:

Compressor, DeflatingCompressor

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decompressor

protected Decompressor decompressor

Reference to the real decompression engine that must follow the Decompressor interface.

See Also:

Decompressor, InflatingDecompressor

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interpolator

protected Interpolator interpolator

Reference to the real statistical modeler that must follow the Interpolator interface.

See Also:

Interpolator, LinearInterpolator

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in

protected java.io.InputStream in

Reference to the real input stream as provided by the plain-old socket factory, tipically PlainSocketImpl.

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out

protected java.io.OutputStream out

Reference to the real output stream as provided by the plain-old socket factory, tipically PlainSocketImpl.

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zin

protected ZInputStream zin

This input stream represents the input to the compression engine. It is the reference passed when getInputStream 55 is invoked. IMHO it's interesting to see how it is realized because it's an infinite data queue.

See Also:

ZInputStream

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zout

protected ZOutputStream zout

This output stream represents the output coming from the compression engine. It is the reference passed when getOutputStream 55 is invoked.

See Also:

ZOutputStream

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listeners

protected java.util.Hashtable listeners

List of objects waiting for ack. This hashtable is indexed by sequence number and contains objects of Listener type. Every Listener waits for a single ack packet and is responsible for the update of the statistical interpolator.

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myself

protected java.lang.Thread myself

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notStop

protected boolean notStop

This variable drive the main loop: a false value will stop the thread and prepare for exit. The value can be changed using the stop 55 method.

Constructor Detail

Connector

public Connector(java.io.InputStream in,
                 java.io.OutputStream out)
          throws java.lang.Exception

This constructor is used when the connector is not yet started and it is request by the method getInputStream 55 of our socket implementation. It's perfectly specular (but non identical) to the next constructor. Here the question is that, like with Object{Input | Output}Stream class, on client side you should open output then input streams and on server side you should do the converse, because the stream opening causes handshaking packet to be exchanged between the ObjectOutputStream on client and ObjectInputStream on server. If you open the two output (on both client and server) they'll send handshacking packets that nobody receive and answer because no input stream is opened yet.

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Connector

public Connector(java.io.OutputStream out,
                 java.io.InputStream in)
          throws java.lang.Exception

See the previous constructor keeping in mind this one works for getOutputStream 55

Method Detail

create

protected void create()
               throws java.lang.Exception

This internal method is the common part of constructors. It's responsible for command-line options gathering through the properties set. Actually recognized property set is:

• compressor - to load a different compression engine (default: DeflatingCompressor)
• decompressor - to load a different decompression engine (default: InflatingDecompressor)
• interpolator - to load a different statistical modeler (default: LinearInterpolator)
Classes referenced through properties must be present into the classpath or must be loadable through invocation of the standard method {#link java.lang.Class#forName(String) forName}. The method getLevels() 55 is used to retrieve the number of supported compression level and to initialize the interpolator using the appropriate number of levels. Finally, the main loop is started through thread creation.

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decompress

protected byte[] decompress(byte[] buf)
                     throws java.io.IOException

This method is responsible for data decompression. It uses the loaded decompression engine (or InflatingDecompressor if not provided) and a ByteArrayInputStream (that renders a byte array as an input stream) to build an InflaterInputStream that "reads" compressed data and write "uncompressed data".

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compress

protected byte[] compress(byte[] buf)
                   throws java.io.IOException

This method is responsible for data compression. It uses the loaded compression engine (or DeflatingCompressor if not provided) and a ByteArrayOutputStream (that renders an output stream as a byte array) to build a DeflaterOutputStream that "writes" uncompressed data and read "compressed data".

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run

public void run()

The main loop. Here packets get captured and converted into ZObjects to see if they are normal compressed or ack. In the first case, data gets decompressed and queued into the ZInputStream that can be given out as the primary input stream (through the method getInputStream 55 and an ack packet is immediately sent back. In the case of a received ack, the appropriate listener gets notified of the arriving ack and it will provide to update the interpolator.

Specified by:

run in interface java.lang.Runnable

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sendAck

public void sendAck(ZObject zobj)
             throws java.io.IOException

An ack is sent through this method, based on the passed ZObject that's the received one. From that object it gets the sequence number and use it to build an ack-type ZObject. Then the latter is "serialized" and transformed into a byte array , ready to be sent through the real output stream (as provided by the previous socket factory). We don't use standard serialization because the object's type domain is really limited (only one class) and the resulting overhead would not be justified.

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send

public void send(byte[] data)
          throws java.io.IOException

This method is invoked by the ZoutputStream.flush 55 method to perform the real data sending. Basically it performs the following tasks:

• ask the interpolator to compute a suitable compression level based on data buffer dimension,
• set the compression engine to work at that level
• compress data and acquire compression time
• build ZObject, serialize it and send
• install a new Listener object, waiting for ack to update the interpolator

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getInputStream

public java.io.InputStream getInputStream()

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getOutputStream

public java.io.OutputStream getOutputStream()

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stop

public void stop()

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