edu.berkeley.cs186.database.io

Class Page

java.lang.Object

edu.berkeley.cs186.database.io.Page

public class Page
extends Object

General-purpose wrapper for interacting with the memory-mapped bytes on a page. YOU SHOULD NOT NEED TO CHANGE ANY OF THE CODE IN THIS PACKAGE.

Field Summary

Fields

Modifier and Type	Field and Description
static int	pageSize

Constructor Summary

Constructors

Constructor and Description
Page(FileChannel fc, int blockNum, int pageNum) Create a new page using fc with at offset blockNum with virtual page number pageNum
Page(FileChannel fc, int blockNum, int pageNum, boolean durable)

Method Summary

Methods

Modifier and Type	Method and Description
void	flush() Force the page to disk.
int	getPageNum()
byte	readByte(int position) Read the single byte at offset position.
byte[]	readBytes() Read all the bytes in file.
byte[]	readBytes(int position, int num) Reads num bytes from offset position and returns them in a new byte array.
void	readBytes(int position, int num, byte[] buf) Reads num bytes from offset position into buf.
int	readInt(int startPos) Read a 4-byte integer from the page at offset startPos.
void	wipe() Completely wipe (zero out) the page.
void	writeByte(int position, byte b) Write a single byte into the file at offset position.
void	writeBytes(int position, int num, byte[] buf) Write num bytes from buf at offset position.
void	writeInt(int startPos, int value) Write a 4-byte integer into the page at offset startPos.

Methods inherited from class java.lang.Object

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

Field Detail

pageSize

public static final int pageSize

See Also:

Constant Field Values

Constructor Detail

Page

public Page(FileChannel fc,
    int blockNum,
    int pageNum)

Create a new page using fc with at offset blockNum with virtual page number pageNum

Parameters:

fc - the file channel for this Page

blockNum - the block in the file for this page

pageNum - the virtual page number

Page

public Page(FileChannel fc,
    int blockNum,
    int pageNum,
    boolean durable)

Method Detail

readBytes

public void readBytes(int position,
             int num,
             byte[] buf)

Reads num bytes from offset position into buf.

Parameters:

position - the offset in the page to read from

num - the number of bytes to read

buf - the buffer to put the bytes into

readBytes

public byte[] readBytes(int position,
               int num)

Reads num bytes from offset position and returns them in a new byte array.

Parameters:

position - the offset in the page to read from

num - the number of bytes to read

Returns:

a new byte array with the bytes read

readBytes

public byte[] readBytes()

Read all the bytes in file.

Returns:

a new byte array with all the bytes in the file

readByte

public byte readByte(int position)

Read the single byte at offset position.

Parameters:

position - the offest in the page to read from

Returns:

the byte at offset position

writeBytes

public void writeBytes(int position,
              int num,
              byte[] buf)

Write num bytes from buf at offset position.

Parameters:

position - the offest in the file to write to

num - the number of bytes to write

buf - the source for the write

writeByte

public void writeByte(int position,
             byte b)

Write a single byte into the file at offset position.

Parameters:

position - the offset in the file to write to

b - the byte to write

writeInt

public void writeInt(int startPos,
            int value)

Write a 4-byte integer into the page at offset startPos.

Parameters:

startPos - the offset in the file to write to

value - the value to write

readInt

public int readInt(int startPos)

Read a 4-byte integer from the page at offset startPos.

Parameters:

startPos - the offset in the file to read from

Returns:

the 4-byte integer at startPos

wipe

public void wipe()

Completely wipe (zero out) the page.

flush

public void flush()

Force the page to disk.

getPageNum

public int getPageNum()

Returns:

the virtual page number of this page