info.monitorenter.util.collections
Class RingBufferArrayFast<T>

java.lang.Object
  info.monitorenter.util.collections.RingBufferArrayFast<T>

Type Parameters:

T - the type of instances to store.

All Implemented Interfaces:

IRingBuffer<T>, java.io.Serializable, java.lang.Cloneable, java.lang.Iterable<T>

Direct Known Subclasses:

RingBufferArray

public class RingBufferArrayFast<T>
extends java.lang.Object
implements java.lang.Cloneable, IRingBuffer<T>

Fast ring buffer implementation.

This implementation differs from the RingBufferArray in one point:
If setBufferSize(int asize) decreases the size of the buffer and it will get smaller than the actual amount of elements stored, they will get lost. This avoids the need for an internal List to store elements overhanging. Some tests may be left out that may speed up this IRingBuffer. Adding 5000000 elements was about 25 % faster compared to the RingBufferArray on an Athlon 1200, 256 MB RAM.

For allowing high performance single-threaded use this implementation and the implementations of the retrievable Iterator- instances are not synchronized at all.

Author:

Achim Westermann

See Also:

Serialized Form

Nested Class Summary

protected class

RingBufferArrayFast.ARingBufferIterator Base for ring buffer iterators that has access to the ring buffer by being an non-static inner class.

Nested classes/interfaces inherited from interface info.monitorenter.util.collections.IRingBuffer

IRingBuffer.RingBufferException

Field Summary

static boolean	DEBUG Flip the switch and you will see how the compiler changes the size of the class file.
protected java.lang.Object[]	m_buffer The internal array used as buffer.
protected boolean	m_empty Flag that marks whether this buffer is empty or not.
protected int	m_headpointer The internal index to buffer where the next element is going to be placed (not placed yet!).
protected int	m_size The internal size of the buffer.
protected int	m_tailpointer The internal index to buffer where the next element is going to be read.

Constructor Summary

RingBufferArrayFast(int aSize)
Constructs a RingBuffer with the given size.

Method Summary

T	add(T anObject) Adds an element to the ring buffer, potentially removing the first element to make more room.
void	clear() Fast method to clear the buffer - only needs to set three primitive members.
protected java.lang.Object	clone()
boolean	equals(java.lang.Object obj)
int	getBufferSize() Returns the absolute amount of space in the buffer.
T	getOldest() Returns the oldest element from the buffer.
T	getYoungest() Returns the last element added.
int	hashCode()
boolean	isEmpty() Tests whether no elements are stored in the buffer.
boolean	isFull() Returns true if no more space in the buffer is available.
java.util.Iterator<T>	iterator() Delegates to iteratorL2F().
java.util.Iterator<T>	iteratorF2L() Returns an Iterator that will return the elements in exactly the inverse order the subsequent call to remove() would do.
java.util.Iterator<T>	iteratorL2F() Returns an Iterator that will return the elements in exactly the order the subsequent call to remove() would do.
T	remove() Removes the oldest element from the buffer.
T[]	removeAll() Clears the buffer.
void	setBufferSize(int newSize) Sets a new buffer- size.
int	size() Returns the actual amount of elements stored in the buffer.
java.lang.String	toString() Returns a string representation of the RingBuffer and it's contents.

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

DEBUG

public static final boolean DEBUG

Flip the switch and you will see how the compiler changes the size of the class file.

See Also:

Constant Field Values

m_buffer

protected java.lang.Object[] m_buffer

The internal array used as buffer.

m_empty

protected boolean m_empty

Flag that marks whether this buffer is empty or not.

 
             headpointer
              |
        +---+---+---+---+
        | 0 | 1 | 2 | 3 |
        +---+---+---+---+
              |
             tailpointer
    
        From where to where are the elements?
        Where is empty space?
        empty == true:  0 elements are contained: buffer empty
        empty == false:  4 elements are contained: buffer full
        remember:
            -the headpointer points to the space where the next element will be inserted.
            -the tailpointer points to the space to read the next element from.
 
 
 

m_headpointer

protected int m_headpointer

The internal index to buffer where the next element is going to be placed (not placed yet!).

m_size

protected int m_size

The internal size of the buffer.

For performance reasons the size of the buffer -1!

m_tailpointer

protected int m_tailpointer

The internal index to buffer where the next element is going to be read.

Constructor Detail

RingBufferArrayFast

public RingBufferArrayFast(int aSize)

Constructs a RingBuffer with the given size.

Parameters:

aSize - the size of the buffer.

Method Detail

add

public T add(T anObject)

Adds an element to the ring buffer, potentially removing the first element to make more room.

Specified by:

add in interface IRingBuffer<T>

Parameters:

anObject - the instance to add.

Returns:

the oldest Object, if RingBuffer was filled with 'maxsize' elements before, or null.

clear

public void clear()

Fast method to clear the buffer - only needs to set three primitive members.

Specified by:

clear in interface IRingBuffer<T>

See Also:

IRingBuffer.clear()

clone

protected java.lang.Object clone()
                          throws java.lang.CloneNotSupportedException

Overrides:

clone in class java.lang.Object

Throws:

java.lang.CloneNotSupportedException

See Also:

Object.clone()

equals

public boolean equals(java.lang.Object obj)

Overrides:

equals in class java.lang.Object

See Also:

Object.equals(java.lang.Object)

getBufferSize

public int getBufferSize()

Description copied from interface: IRingBuffer

Returns the absolute amount of space in the buffer.

Specified by:

getBufferSize in interface IRingBuffer<T>

Returns:

the absolute amount of space in the buffer.

See Also:

IRingBuffer.getBufferSize()

getOldest

public T getOldest()
            throws IRingBuffer.RingBufferException

Description copied from interface: IRingBuffer

Returns the oldest element from the buffer. This method does not remove the element.

Specified by:

getOldest in interface IRingBuffer<T>

Returns:

the oldest element from the buffer.

Throws:

IRingBuffer.RingBufferException - if the buffer is empty.

See Also:

IRingBuffer.getOldest()

getYoungest

public T getYoungest()
              throws IRingBuffer.RingBufferException

Description copied from interface: IRingBuffer

Returns the last element added. This method does not remove the element.

Specified by:

getYoungest in interface IRingBuffer<T>

Returns:

the last element added.

Throws:

IRingBuffer.RingBufferException - if the buffer is empty.

See Also:

IRingBuffer.getYoungest()

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

See Also:

Object.hashCode()

isEmpty

public boolean isEmpty()

Description copied from interface: IRingBuffer

Tests whether no elements are stored in the buffer.

Specified by:

isEmpty in interface IRingBuffer<T>

Returns:

true if no element is stored in the buffer.

See Also:

IRingBuffer.isEmpty()

isFull

public boolean isFull()

Description copied from interface: IRingBuffer

Returns true if no more space in the buffer is available. This method should be used to test before calling IRingBuffer.add(Object).

Specified by:

isFull in interface IRingBuffer<T>

Returns:

true if no more space in the buffer is available.

See Also:

IRingBuffer.isFull()

iterator

public java.util.Iterator<T> iterator()

Delegates to iteratorL2F().

Specified by:

iterator in interface java.lang.Iterable<T>

See Also:

Iterable.iterator()

iteratorF2L

public java.util.Iterator<T> iteratorF2L()

Returns an Iterator that will return the elements in exactly the inverse order the subsequent call to remove() would do.

The youngest elements are returned first. The Iterator returned is not thread- safe!

Specified by:

iteratorF2L in interface IRingBuffer<T>

Returns:

an Iterator that will return the elements in exactly the inverse order the subsequent call to remove() would do.

iteratorL2F

public java.util.Iterator<T> iteratorL2F()

Returns an Iterator that will return the elements in exactly the order the subsequent call to remove() would do.

The oldest elements are returned first. The Iterator returned is not thread- safe!

Specified by:

iteratorL2F in interface IRingBuffer<T>

Returns:

an Iterator that will return the elements in exactly the order the subsequent call to remove() would do.

remove

public T remove()

Description copied from interface: IRingBuffer

Removes the oldest element from the buffer.

Specified by:

remove in interface IRingBuffer<T>

Returns:

the removed oldest element from the buffer.

See Also:

IRingBuffer.remove()

removeAll

public T[] removeAll()

Description copied from interface: IRingBuffer

Clears the buffer. It will return all of it's stored elements.

Specified by:

removeAll in interface IRingBuffer<T>

Returns:

all removed elements.

See Also:

IRingBuffer.removeAll()

setBufferSize

public void setBufferSize(int newSize)

Sets a new buffer- size.

A new size is assigned but the elements "overhanging" are returned by the Object remove()- method first. This may take time until the buffer has its actual size again. Don't pretend on calling this method for saving of memory very often as the whole buffer has to be copied into a new array every time- and if newSize < getSize() additional the overhanging elements references have to be moved to the internal List pendingremove.

Specified by:

setBufferSize in interface IRingBuffer<T>

Parameters:

newSize - the new size of the buffer.

size

public int size()

Description copied from interface: IRingBuffer

Returns the actual amount of elements stored in the buffer.

Specified by:

size in interface IRingBuffer<T>

Returns:

the actual amount of elements stored in the buffer.

See Also:

IRingBuffer.size()

toString

public java.lang.String toString()

Returns a string representation of the RingBuffer and it's contents.

Don't call this in your application too often: hard arraycopy - operation an malloc are triggered.

Overrides:

toString in class java.lang.Object

Returns:

a string representation of the RingBuffer and it's contents.