org.apache.catalina.cluster.io
Class XByteBuffer

java.lang.Object
  org.apache.catalina.cluster.io.XByteBuffer

public class XByteBuffer

extends java.lang.Object

The XByteBuffer provides a dual functionality. One, it stores message bytes and automatically extends the byte buffer if needed.
Two, it can encode and decode packages so that they can be defined and identified as they come in on a socket.
Transfer package:

• START_DATA/b> - 7 bytes - FLT2002
• COMPRESS - 4 bytes - is message compressed flag
• SIZE - 4 bytes - size of the data package
• DATA - should be as many bytes as the prev SIZE
• END_DATA - 7 bytes - TLF2003

FIXME: Why we not use a list of byte buffers? FIXME: Used a pool of buffers instead, every time new generation

Version:

$Id: XByteBuffer.java 939539 2010-04-30 01:31:33Z kkolinko $

Author:

Filip Hanik, Peter Rossbach

Field Summary

protected byte[]	buf Variable to hold the data
protected int	bufSize Current length of data in the buffer
static byte[]	END_DATA This is the package footer, 7 bytes (TLF2003)
static org.apache.commons.logging.Log	log
static byte[]	START_DATA This is a package header, 7 bytes (FLT2002)

Constructor Summary

XByteBuffer()
Constructs a new XByteBuffer with an initial size of 1024 bytes

XByteBuffer(int size)
Constructs a new XByteBuffer

Method Summary

boolean	append(byte[] b, int off, int len) Appends the data to the buffer.
void	clear() Resets the buffer
int	countPackages() Internal mechanism to make a check if a complete package exists within the buffer
static byte[]	createDataPackage(byte[] indata, int compressed) Creates a complete data package
boolean	doesPackageExist() Method to check if a package exists in this byte buffer.
ClusterData	extractPackage(boolean clearFromBuffer) Extracts the message bytes from a package.
static int	firstIndexOf(byte[] src, int srcOff, byte[] find) Similar to a String.IndexOf, but uses pure bytes
byte[]	getBytes() Returns the bytes in the buffer, in its exact length
static byte[]	toBytes(int n) Converts an integer to four bytes
static byte[]	toBytes(long n) Converts an long to eight bytes
static int	toInt(byte[] b, int off) Convert four bytes to an int
static long	toLong(byte[] b, int off) Convert eight bytes to a long

Methods inherited from class java.lang.Object

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

Field Detail

log

public static org.apache.commons.logging.Log log

START_DATA

public static final byte[] START_DATA

This is a package header, 7 bytes (FLT2002)

END_DATA

public static final byte[] END_DATA

This is the package footer, 7 bytes (TLF2003)

buf

protected byte[] buf

Variable to hold the data

bufSize

protected int bufSize

Current length of data in the buffer

Constructor Detail

XByteBuffer

public XByteBuffer(int size)

Constructs a new XByteBuffer

Parameters:

size - - the initial size of the byte buffer

XByteBuffer

public XByteBuffer()

Constructs a new XByteBuffer with an initial size of 1024 bytes

Method Detail

getBytes

public byte[] getBytes()

Returns the bytes in the buffer, in its exact length

clear

public void clear()

Resets the buffer

append

public boolean append(byte[] b,
                      int off,
                      int len)

Appends the data to the buffer. If the data is incorrectly formatted, ie, the data should always start with the header, false will be returned and the data will be discarded.

Parameters:

b - - bytes to be appended

off - - the offset to extract data from

len - - the number of bytes to append.

Returns:

true if the data was appended correctly. Returns false if the package is incorrect, ie missing header or something, or the length of data is 0

countPackages

public int countPackages()

Internal mechanism to make a check if a complete package exists within the buffer

Returns:

- true if a complete package (header,compress,size,data,footer) exists within the buffer

doesPackageExist

public boolean doesPackageExist()

Method to check if a package exists in this byte buffer.

Returns:

- true if a complete package (header,compress,size,data,footer) exists within the buffer

extractPackage

public ClusterData extractPackage(boolean clearFromBuffer)
                           throws java.io.IOException

Extracts the message bytes from a package. If no package exists, a IllegalStateException will be thrown.

Parameters:

clearFromBuffer - - if true, the package will be removed from the byte buffer

Returns:

- returns the actual message bytes (header, compress,size and footer not included).

Throws:

java.io.IOException

toInt

public static int toInt(byte[] b,
                        int off)

Convert four bytes to an int

Parameters:

b - - the byte array containing the four bytes

off - - the offset

Returns:

the integer value constructed from the four bytes

Throws:

java.lang.ArrayIndexOutOfBoundsException

toLong

public static long toLong(byte[] b,
                          int off)

Convert eight bytes to a long

Parameters:

b - - the byte array containing the four bytes

off - - the offset

Returns:

the long value constructed from the eight bytes

Throws:

java.lang.ArrayIndexOutOfBoundsException

toBytes

public static byte[] toBytes(int n)

Converts an integer to four bytes

Parameters:

n - - the integer

Returns:

- four bytes in an array

toBytes

public static byte[] toBytes(long n)

Converts an long to eight bytes

Parameters:

n - - the long

Returns:

- eight bytes in an array

firstIndexOf

public static int firstIndexOf(byte[] src,
                               int srcOff,
                               byte[] find)

Similar to a String.IndexOf, but uses pure bytes

Parameters:

src - - the source bytes to be searched

srcOff - - offset on the source buffer

find - - the string to be found within src

Returns:

- the index of the first matching byte. -1 if the find array is not found

createDataPackage

public static byte[] createDataPackage(byte[] indata,
                                       int compressed)
                                throws java.io.IOException

Creates a complete data package

Parameters:

indata - - the message data to be contained within the package

compressed - - compression flag for the indata buffer

Returns:

- a full package (header,compress,size,data,footer)

Throws:

java.io.IOException