com.sun.jimi.core.vmem
Class PageFrame

java.lang.Object
  |
  +--com.sun.jimi.core.vmem.PageFrame

Direct Known Subclasses:

BytePageFrame, IntPageFrame

public abstract class PageFrame

extends java.lang.Object

Base class for in-memory buffers representing pages of paged data. Maintains some useful state: Whether the data in the frame has been modified, when the page was last accessed, and which logical page it represents. Subclasses must implement the I/O code for swapping page frames to and from streams.

Field Summary

protected int	logicalPageNumber logical page number represented by the page frame
protected boolean	modified true if the page is marked as modified
protected long	timeStamp timestamp of last use

Constructor Summary

PageFrame()

Method Summary

int	getLogicalPageNumber() Get the logical page number this frame represents.
boolean	isModified() Check if the page frame has been modified in memory.
long	lastTouched() Return the time for when the frame was last touched.
abstract void	readFrom(java.io.InputStream input) Read in page data from an input stream.
void	setLogicalPageNumber(int pageNumber) Set the logical page number this frame represents.
void	setModified(boolean flag) Set whether the page frame is marked as modified
void	touch() Update the timestamp to the present time.
abstract void	writeTo(java.io.OutputStream output) Write the page to an output stream.

Methods inherited from class java.lang.Object

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

Field Detail

modified

protected boolean modified

true if the page is marked as modified

logicalPageNumber

protected int logicalPageNumber

logical page number represented by the page frame

timeStamp

protected long timeStamp

timestamp of last use

Constructor Detail

PageFrame

public PageFrame()

Method Detail

isModified

public boolean isModified()

Check if the page frame has been modified in memory.

Returns:

true if the page is marked as modified

setModified

public void setModified(boolean flag)

Set whether the page frame is marked as modified

Parameters:

flag - true if the frame is being marked as modified

setLogicalPageNumber

public void setLogicalPageNumber(int pageNumber)

Set the logical page number this frame represents.

Parameters:

pageNumber - the logical page number

getLogicalPageNumber

public int getLogicalPageNumber()

Get the logical page number this frame represents.

Returns:

the page number

writeTo

public abstract void writeTo(java.io.OutputStream output)
                      throws java.io.IOException

Write the page to an output stream.

Parameters:

output - the stream to write to

readFrom

public abstract void readFrom(java.io.InputStream input)
                       throws java.io.IOException

Read in page data from an input stream.

Parameters:

input - the stream to read from

lastTouched

public long lastTouched()

Return the time for when the frame was last touched.

Returns:

the time as a long

touch

public void touch()

Update the timestamp to the present time.