Class PTE

java.lang.Object
  |
  +--PTE

public class PTE

extends java.lang.Object

A PTE represents a memory page table entry.

Field Summary

static int	NUM_CLASSES PTE.NUM_CLASSES is the number of reference classes used in the reference class field of a page table entry.
static int	PERMISSION_BITS PTE.PERMISSION_BITS is the number of permission bits and the number of reference class bits in a page table entry.

Constructor Summary

PTE(int pn)
new PTE(pn) returns a new page table entry with page number pn.

Method Summary

void	assignFrame(int fn) pte.assignFrame(fn) sets the frame number for pte to fn and sets its present bit to 1.
int	getFrameNumber() pte.getFrameNumber() returns the frame number currently assigned to the page that is controlled by pte or -1 if if there is no frame assigned to the page.
int	getPermissions() pte.getPermissions() returns the permission bits of pte.
int	getRefClass() pte.getRefClass() returns the reference class bits of pte.
boolean	isDirty() pte.isDirty() returns true if the page controlled by pte has been recently written.
boolean	isPresent() pte.isPresent() returns the present bit of pte.
boolean	isReferenced() pte.isReferenced() returns true if the page controlled by pte has been recently referenced.
void	print() pte.print() writes pte to System.out in tabular form.
static void	printHeader() PTE.printHeader() writes a header for tables containing pte entries printed with the print() method.
void	releaseFrame() pte.releaseFrame() clears the frame number and present bit of pte.
void	resetDirtyBit() pte.resetDirtyBit() resets the reference bit in pte.
void	resetReferenceBit() pte.resetReferenceBit() resets the reference bit in pte.
void	setFrameNumber(int n) pte.setFrameNumber(n) sets the frame number for the page that is controlled by pte to n.
void	setPermissions(int p) pte.setPermissions(p) sets the permission bits of pte from p.
void	setPresent(boolean b) pte.setPresent(b) sets the present bit of pte to b.
void	setRefClass(int c) pte.setRefClass(c) sets the reference class bits of pte from c.

Methods inherited from class java.lang.Object

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

Field Detail

PERMISSION_BITS

public static final int PERMISSION_BITS

PTE.PERMISSION_BITS is the number of permission bits and the number of reference class bits in a page table entry.

See Also:

Constant Field Values

NUM_CLASSES

public static final int NUM_CLASSES

PTE.NUM_CLASSES is the number of reference classes used in the reference class field of a page table entry.

See Also:

Constant Field Values

Constructor Detail

PTE

public PTE(int pn)

new PTE(pn) returns a new page table entry with page number pn.

Method Detail

isPresent

public boolean isPresent()

pte.isPresent() returns the present bit of pte. This bit is true if the page represented by pte is currently in physical memory.

setPresent

public void setPresent(boolean b)

pte.setPresent(b) sets the present bit of pte to b.

getPermissions

public int getPermissions()

pte.getPermissions() returns the permission bits of pte. The individual permission bits can be accessed by bitwise ANDing with MMU.READ, MMU.WRITE, or MMU.FETCH, and checking if the result is non-zero.

setPermissions

public void setPermissions(int p)

pte.setPermissions(p) sets the permission bits of pte from p. This parameter shoud be a bitwise OR of the desired constants MMU.READ, MMI.WRITE, e MMU.READ, and MMU.FETCH.

resetReferenceBit

public void resetReferenceBit()

pte.resetReferenceBit() resets the reference bit in pte.

isReferenced

public boolean isReferenced()

pte.isReferenced() returns true if the page controlled by pte has been recently referenced.

resetDirtyBit

public void resetDirtyBit()

pte.resetDirtyBit() resets the reference bit in pte.

isDirty

public boolean isDirty()

pte.isDirty() returns true if the page controlled by pte has been recently written.

getRefClass

public int getRefClass()

pte.getRefClass() returns the reference class bits of pte. The individual reference class bits can be accessed by bitwise ANDing with MMU.READ, MMU.WRITE, or MMU.FETCH, and checking if the result is non-zero.

setRefClass

public void setRefClass(int c)

pte.setRefClass(c) sets the reference class bits of pte from c. This parameter shoud be a bitwise OR of the desired constants MMU.READ, MMI.WRITE, and MMU.FETCH.

getFrameNumber

public int getFrameNumber()

pte.getFrameNumber() returns the frame number currently assigned to the page that is controlled by pte or -1 if if there is no frame assigned to the page.

setFrameNumber

public void setFrameNumber(int n)

pte.setFrameNumber(n) sets the frame number for the page that is controlled by pte to n.

assignFrame

public void assignFrame(int fn)

pte.assignFrame(fn) sets the frame number for pte to fn and sets its present bit to 1.

releaseFrame

public void releaseFrame()

pte.releaseFrame() clears the frame number and present bit of pte.

printHeader

public static void printHeader()

PTE.printHeader() writes a header for tables containing pte entries printed with the print() method.

print

public void print()

pte.print() writes pte to System.out in tabular form.