org.mwolff.struts.back
Class RingBuffer

java.lang.Object
  org.mwolff.struts.back.RingBuffer

public class RingBuffer
extends java.lang.Object

A Ringbuffer is a buffer to store something (in this case ArrayEntries). This buffer is made for the stuts back mechanism. Its supports also a wizzard manner to go back and forward more steps. This implementation simulates a ringbuffer. The Buffer has the following invariants:

• The actIndex pointer shows to the act index to be shown.
• All Entries from startPoint to endPoint are valid entries if both pointers are >= 0.
• If maxindex is reached the first index will be overide and the overflow flag is set.

Example: startPoint = 0; endPoint = 5; actIndex = 4;

1. There are 6 valid entries from 0 to 5.
2. The actal index ist 4. So you can go forward 1 entry and you can go backword 4 entries.
3. A New Entry will be inserted on index 6, the endpoint will be increased

Since:

1.0

Author:

Manfred Wolff

Field Summary

protected static org.apache.commons.logging.Log

log Commons Logging instance.

Constructor Summary

RingBuffer()
Constructor with default entries (40).

RingBuffer(int maxEntries)
Constructor with an amount of entries.

Method Summary

ArrayEntry	back() Goes one entry back into the ringbuffer.
void	clear() Clears the buffer
ArrayEntry	forward() Goes one entry forward in the ringbuffer.
ArrayEntry	getActIndex()
ArrayEntry	getLastPushed() Returns the last pushed entry.
boolean	isBackPossible()
boolean	isForwardPossible()
boolean	isNoPush() Returns the NoPush Flag.
boolean	isOverflow() Returns the overflow bit.
boolean	isWereInvolved() Returns the WereInvolved Flag.
void	print()
int	push(ArrayEntry entry) Pushes an entry into the ringbuffer.
void	setNoPush(boolean noPush) Sets the NoPush Flag.
void	setWereInvolved(boolean wereInvolved) Sets the WereInvolved Flag.
int	size()

Methods inherited from class java.lang.Object

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

Field Detail

log

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

Commons Logging instance.

Constructor Detail

RingBuffer

public RingBuffer()

Constructor with default entries (40).

RingBuffer

public RingBuffer(int maxEntries)

Constructor with an amount of entries.

Parameters:

maxEntries - Entries of the ringbuffer.

Method Detail

isForwardPossible

public boolean isForwardPossible()

isBackPossible

public boolean isBackPossible()

print

public void print()

clear

public void clear()

Clears the buffer

size

public int size()

Returns:

The maximal entries of the buffer.

push

public int push(ArrayEntry entry)

Pushes an entry into the ringbuffer.

Parameters:

entry - The entry to be pushed

Returns:

The actual index of the ringbuffer

back

public ArrayEntry back()

Goes one entry back into the ringbuffer.

Returns:

The entry back

forward

public ArrayEntry forward()

Goes one entry forward in the ringbuffer.

Returns:

The entry forward

getLastPushed

public ArrayEntry getLastPushed()

Returns the last pushed entry.

Returns:

The last pushed entry

getActIndex

public ArrayEntry getActIndex()

isOverflow

public boolean isOverflow()

Returns the overflow bit.

Returns:

the overflow bit.

isNoPush

public boolean isNoPush()

Returns the NoPush Flag.

Returns:

The NoPush Flag.

setNoPush

public void setNoPush(boolean noPush)

Sets the NoPush Flag.

Parameters:

noPush - The NoPush Flag.

isWereInvolved

public boolean isWereInvolved()

Returns the WereInvolved Flag.

Returns:

The WereInvolved Flag.

setWereInvolved

public void setWereInvolved(boolean wereInvolved)

Sets the WereInvolved Flag.

Parameters:

wereInvolved - The WereInvolved Flag.