org.jgroups.nio

Class Buffers

java.lang.Object

org.jgroups.nio.Buffers

All Implemented Interfaces:

java.lang.Iterable<java.nio.ByteBuffer>

public class Buffers
extends java.lang.Object
implements java.lang.Iterable<java.nio.ByteBuffer>

Class to do scattering reads or gathering writes on a sequence of ByteBuffer instances. The buffers are kept in an array with fixed capacity (max Short.MAX_VALUE). Buffers can be added and removed dynamically (they're dropped when the capacity is exceeded).

A read is successful when all non-null buffers from left to right are filled, ie. all Buffer.remaining() methods return 0.

Same for writes: when all non-null buffers (from left to right) have been written (Buffer.remaining() == 0), a write is considered successful; otherwise it is partial.

Individual buffers can be accessed; e.g. for reading its value after a read. It is also possible to add buffers dynamically, e.g. after reading a 'length' buffer, a user may want to add a new buffer allocated for reading 'length' bytes.

This class is not synchronized.

Since:

3.6.5

Author:

Bela Ban

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected class	Buffers.BuffersIterator Iterates over the non-null buffers

Field Summary

Fields

Modifier and Type	Field and Description
protected java.nio.ByteBuffer[]	bufs
protected short	limit
protected short	next_to_copy
protected short	position

Constructor Summary

Constructors

Constructor and Description
Buffers(java.nio.ByteBuffer... data)
Buffers(int capacity) Creates a new instance with an array of capacity buffers

Method Summary

Modifier and Type	Method and Description
Buffers	add(java.nio.ByteBuffer... buffers)
Buffers	add(java.nio.ByteBuffer buf)
protected boolean	adjustPosition(boolean null_complete_data)
protected static void	assertPositiveUnsignedShort(int num)
Buffers	copy() Copies the data that has not yet been written and moves last_copied.
static java.nio.ByteBuffer	copyBuffer(java.nio.ByteBuffer buf) Copies a ByteBuffer by copying and wrapping the underlying array of a heap-based buffer.
java.nio.ByteBuffer	get(int index)
boolean	hasRemaining()
java.util.Iterator<java.nio.ByteBuffer>	iterator()
int	limit()
Buffers	limit(int new_limit)
protected boolean	makeSpace()
int	nextToCopy()
Buffers	nextToCopy(int next)
protected boolean	nullData() Looks at all buffers in range [position ..
int	position()
Buffers	position(int new_pos)
boolean	read(java.nio.channels.SocketChannel ch) Performs a scattering read into all (contiguous) non-null buffers in range [position ..
java.nio.ByteBuffer	readLengthAndData(java.nio.channels.SocketChannel ch) Reads length and then length bytes into the data buffer, which is grown if needed.
int	remaining()
Buffers	remove(int index) Nulls the buffer at index
Buffers	set(int index, java.nio.ByteBuffer buf)
int	size() Returns the number of elements that have not yet been read or written
protected boolean	spaceAvailable(int num_buffers)
protected static short	toPositiveUnsignedShort(int num)
java.lang.String	toString()
boolean	write(java.nio.channels.GatheringByteChannel ch) Writes the buffers from position to limit to the given channel.
boolean	write(java.nio.channels.GatheringByteChannel ch, java.nio.ByteBuffer... buffers) Helper method which adds the buffers passed as arguments and then calls write()

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Field Detail

bufs

protected final java.nio.ByteBuffer[] bufs

position

protected short position

limit

protected short limit

next_to_copy

protected short next_to_copy

Constructor Detail

Buffers

public Buffers(int capacity)

Creates a new instance with an array of capacity buffers

Parameters:

capacity - Must be an unsigned positive short [1 .. Short.MAX_VALUE]

Buffers

public Buffers(java.nio.ByteBuffer... data)

Method Detail

position

public int position()

position

public Buffers position(int new_pos)

limit

public int limit()

limit

public Buffers limit(int new_limit)

nextToCopy

public int nextToCopy()

nextToCopy

public Buffers nextToCopy(int next)

remaining

public int remaining()

hasRemaining

public boolean hasRemaining()

add

public Buffers add(java.nio.ByteBuffer... buffers)

add

public Buffers add(java.nio.ByteBuffer buf)

get

public java.nio.ByteBuffer get(int index)

set

public Buffers set(int index,
                   java.nio.ByteBuffer buf)

remove

public Buffers remove(int index)

Nulls the buffer at index

readLengthAndData

public java.nio.ByteBuffer readLengthAndData(java.nio.channels.SocketChannel ch)
                                      throws java.lang.Exception

Reads length and then length bytes into the data buffer, which is grown if needed.

Parameters:

ch - The channel to read data from

Returns:

The data buffer (position is 0 and limit is length), or null if not all data could be read.

Throws:

java.lang.Exception

read

public boolean read(java.nio.channels.SocketChannel ch)
             throws java.lang.Exception

Performs a scattering read into all (contiguous) non-null buffers in range [position .. limit]. Returns true if the scattering read was successful, else false. Note that to read the contents of the individual buffers, Buffer.clear() has to be called (all buffers have their position == limit on a successfull read).

Throws:

java.lang.Exception

write

public boolean write(java.nio.channels.GatheringByteChannel ch,
                     java.nio.ByteBuffer... buffers)
              throws java.lang.Exception

Helper method which adds the buffers passed as arguments and then calls write()

Throws:

java.lang.Exception

write

public boolean write(java.nio.channels.GatheringByteChannel ch)
              throws java.lang.Exception

Writes the buffers from position to limit to the given channel. Note that all buffers need to have their Buffer.position at the start of the data to be written be at the start of the data to be written.

Parameters:

ch - The channel to write to

Returns:

True if all the bytes of the buffer were written successfully, false otherwise (partial write).

Throws:

java.lang.Exception - Thrown if the write failed

copy

public Buffers copy()

Copies the data that has not yet been written and moves last_copied. Typically done after an unsuccessful write, if copying is required. This is typically needed if the output buffer is reused. Note that direct buffers will be converted to heap-based buffers

size

public int size()

Returns the number of elements that have not yet been read or written

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

spaceAvailable

protected boolean spaceAvailable(int num_buffers)

makeSpace

protected boolean makeSpace()

nullData

protected boolean nullData()

Looks at all buffers in range [position .. limit-1] and nulls buffers that have no remaining data. Returns true if all buffers could be nulled, and false otherwise

adjustPosition

protected boolean adjustPosition(boolean null_complete_data)

toPositiveUnsignedShort

protected static short toPositiveUnsignedShort(int num)

assertPositiveUnsignedShort

protected static void assertPositiveUnsignedShort(int num)

copyBuffer

public static java.nio.ByteBuffer copyBuffer(java.nio.ByteBuffer buf)

Copies a ByteBuffer by copying and wrapping the underlying array of a heap-based buffer. Direct buffers are converted to heap-based buffers

iterator

public java.util.Iterator<java.nio.ByteBuffer> iterator()

Specified by:

iterator in interface java.lang.Iterable<java.nio.ByteBuffer>