global
Class AbstractBufMgrReplacer

java.lang.Object
  global.AbstractBufMgrReplacer

All Implemented Interfaces:

GlobalConst

Direct Known Subclasses:

Replacer

public abstract class AbstractBufMgrReplacer

extends java.lang.Object

implements GlobalConst

A super class for buffer pool replacement algorithm. It describes which frame to be picked up for replacement by a certain replace algorithm.

Field Summary

static int	Available
static int	Pinned
static int	Referenced

Fields inherited from interface global.GlobalConst

INVALID_PAGE, MAX_NAME, MAXATTRNAME, MAXFILENAME, MAXINDEXNAME, MINIBASE_BUFFER_POOL_SIZE, MINIBASE_DB_SIZE, MINIBASE_DEFAULT_SHAREDMEM_SIZE, MINIBASE_MAX_TRANSACTIONS, MINIBASE_MAXARRSIZE, NUMBUF, PAGE_SIZE, PAGESIZE

Constructor Summary

AbstractBufMgrReplacer()

AbstractBufMgrReplacer(AbstractBufMgr javamgr)
Creates a replacer object.

Method Summary

abstract void	free(int frameNo) Frees and unpins a page in the buffer pool.
abstract int	getNumUnpinnedBuffers() Counts the unpinned frames (free frames) in the buffer pool.
abstract java.lang.String	name() Retruns the name of the replacer algorithm.
abstract int	pick_victim() Must pin the returned frame.
abstract void	pin(int frameNo) Pins a candidate page in the buffer pool.
void	setBufferManager(AbstractBufMgr mgrArg) Sets the buffer manager to be eqaul to the buffer manager in the argument, gets the total number of buffer frames, and mainstains the head of the clock.
abstract boolean	unpin(int frameNo) Unpins a page in the buffer pool.

Methods inherited from class java.lang.Object

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

Field Detail

Available

public static final int Available

See Also:

Constant Field Values

Referenced

public static final int Referenced

See Also:

Constant Field Values

Pinned

public static final int Pinned

See Also:

Constant Field Values

Constructor Detail

AbstractBufMgrReplacer

public AbstractBufMgrReplacer()

AbstractBufMgrReplacer

public AbstractBufMgrReplacer(AbstractBufMgr javamgr)

Creates a replacer object.

Method Detail

pin

public abstract void pin(int frameNo)
                  throws InvalidFrameNumberException

Pins a candidate page in the buffer pool.

Parameters:

frameNo - frame number of the page.

Returns:

true if successful.

Throws:

InvalidFrameNumberException - if the frame number is less than zero or bigger than number of buffers.

unpin

public abstract boolean unpin(int frameNo)
                       throws InvalidFrameNumberException,
                              PageUnpinnedException

Unpins a page in the buffer pool.

Parameters:

frameNo - frame number of the page.

Returns:

true if successful.

Throws:

InvalidFrameNumberException - if the frame number is less than zero or bigger than number of buffers.

PageUnpinnedException - if the page is originally unpinned.

free

public abstract void free(int frameNo)
                   throws PagePinnedException

Frees and unpins a page in the buffer pool.

Parameters:

frameNo - frame number of the page.

Throws:

PagePinnedException - if the page is pinned.

pick_victim

public abstract int pick_victim()
                         throws BufferPoolExceededException,
                                PagePinnedException

Must pin the returned frame.

Throws:

BufferPoolExceededException

PagePinnedException

name

public abstract java.lang.String name()

Retruns the name of the replacer algorithm.

getNumUnpinnedBuffers

public abstract int getNumUnpinnedBuffers()

Counts the unpinned frames (free frames) in the buffer pool.

setBufferManager

public void setBufferManager(AbstractBufMgr mgrArg)

Sets the buffer manager to be eqaul to the buffer manager in the argument, gets the total number of buffer frames, and mainstains the head of the clock.