edu.berkeley.cs186.database.io

Class PageAllocator

java.lang.Object

edu.berkeley.cs186.database.io.PageAllocator

All Implemented Interfaces:

Closeable, AutoCloseable, Iterable<Page>

public class PageAllocator
extends Object
implements Iterable<Page>, Closeable

A PageAllocation system for an OS paging system. Provides memory-mapped paging from the OS, an interface to individual pages with the Page objects, an LRU cache for pages, 16GB worth of paging, and virtual page translation. YOU SHOULD NOT NEED TO CHANGE ANY OF THE CODE IN THIS PACKAGE.

Constructor Summary

Constructors

Constructor and Description
PageAllocator(String fName, boolean wipe) Create a new PageAllocator that writes its bytes into a file named fName.
PageAllocator(String fName, boolean wipe, boolean durable)

Method Summary

Methods

Modifier and Type	Method and Description
int	allocPage() Allocates a new page in the file.
void	close() Close this PageAllocator.
Page	fetchPage(int pageNum) Fetches the page corresponding to virtual page number pageNum.
boolean	freePage(int pageNum) Frees the page to be returned back to the system.
boolean	freePage(Page p) Frees the page to be returned back to the system.
static long	getNumCacheMisses()
static long	getNumIOs()
int	getNumPages()
Iterator<Page>	iterator()

Methods inherited from class java.lang.Object

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

Constructor Detail

PageAllocator

public PageAllocator(String fName,
             boolean wipe)

Create a new PageAllocator that writes its bytes into a file named fName. If wipe is true, the data in the page is completely removed.

Parameters:

fName - the name of the file for this PageAllocator

wipe - a boolean specifying whether to wipe the file

PageAllocator

public PageAllocator(String fName,
             boolean wipe,
             boolean durable)

Method Detail

allocPage

public int allocPage()

Allocates a new page in the file.

Returns:

the virtual page number of the page

fetchPage

public Page fetchPage(int pageNum)

Fetches the page corresponding to virtual page number pageNum.

Parameters:

pageNum - the virtual page number

Returns:

a Page object wrapping the page corresponding to pageNum

freePage

public boolean freePage(Page p)

Frees the page to be returned back to the system. The page is no longer valid and can be re-used the next time the user called allocPage.

Parameters:

p - the page to free

Returns:

whether or not the page was freed

freePage

public boolean freePage(int pageNum)

Frees the page to be returned back to the system. The page is no longer valid and can be re-used the next time the user called allocPage.

Parameters:

pageNum - the virtual page number to be flushed

Returns:

whether or not the page was freed

close

public void close()

Close this PageAllocator.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

getNumPages

public int getNumPages()

getNumIOs

public static long getNumIOs()

getNumCacheMisses

public static long getNumCacheMisses()

iterator

public Iterator<Page> iterator()

Specified by:

iterator in interface Iterable<Page>

Returns:

an iterator of the valid pages managed by this PageAllocator.