org.h2.store
Class DataPage

java.lang.Object
  org.h2.store.DataPage

Direct Known Subclasses:

Data

public class DataPage
extends java.lang.Object

A data page is a byte buffer that contains persistent data of a row or index page.

Field Summary

protected byte[]	data The data itself.
protected DataHandler	handler The data handler responsible for lob objects.
static int	LENGTH_FILLER The space required for the checksum and additional fillers.
static int	LENGTH_INT The length of an integer value.
static int	LENGTH_LONG The length of a long value.
protected int	pos The current write or read position.

Constructor Summary

protected

DataPage(DataHandler handler, byte[] data)

Method Summary

void	check(int len) Test if the checksum is correct.
void	checkCapacity(int plus) Check if there is still enough capacity in the buffer.
static DataPage	create(DataHandler handler, byte[] buff) Create a new data page using the given data for the given handler.
static DataPage	create(DataHandler handler, int capacity) Create a new data page for the given handler.
void	fill(int len) Increase the size to the given length.
void	fillAligned() Fill up the buffer with empty space and an (initially empty) checksum until the size is a multiple of Constants.FILE_BLOCK_SIZE.
byte[]	getBytes() Get the byte array used for this page.
int	getStringLen(java.lang.String s) Get the length of a String value.
int	getValueLen(Value v) Calculate the number of bytes required to encode the given value.
int	length() Get the current write position of this data page, which is the current length.
void	read(byte[] buff, int off, int len) Copy a number of bytes to the given buffer from the current position.
int	readByte() Read one single byte.
DataPage	readDataPageNoSize() Read a data page from this page.
int	readInt() Read an integer at the current position.
long	readLong() Read a long value.
int	readShortInt() Read an short integer at the current position.
java.lang.String	readString() Read a String value.
Value	readValue() Read a value.
void	reset() Set the position to 0.
void	setInt(int pos, int x) Update an integer at the given position.
void	setPos(int pos) Set the current read / write position.
void	updateChecksum() Calculate the checksum and write.
void	write(byte[] buff, int off, int len) Append a number of bytes to this data page.
void	writeByte(byte x) Append one single byte.
void	writeDataPageNoSize(DataPage page) Append the contents of the given data page to this page.
void	writeInt(int x) Write an integer at the current position.
void	writeLong(long x) Append a long value.
void	writeShortInt(int x) Write a short integer at the current position.
void	writeString(java.lang.String s) Write a String value.
void	writeValue(Value v) Append a value.

Methods inherited from class java.lang.Object

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

Field Detail

LENGTH_FILLER

public static final int LENGTH_FILLER

The space required for the checksum and additional fillers.

See Also:

Constant Field Values

LENGTH_INT

public static final int LENGTH_INT

The length of an integer value.

See Also:

Constant Field Values

LENGTH_LONG

public static final int LENGTH_LONG

The length of a long value.

See Also:

Constant Field Values

handler

protected DataHandler handler

The data handler responsible for lob objects.

data

protected byte[] data

The data itself.

pos

protected int pos

The current write or read position.

Constructor Detail

DataPage

protected DataPage(DataHandler handler,
                   byte[] data)

Method Detail

updateChecksum

public void updateChecksum()

Calculate the checksum and write.

check

public void check(int len)
           throws java.sql.SQLException

Test if the checksum is correct.

Parameters:

len - the number of bytes

Throws:

java.sql.SQLException - if the checksum does not match

setInt

public void setInt(int pos,
                   int x)

Update an integer at the given position. The current position is not change.

Parameters:

pos - the position

x - the value

writeInt

public void writeInt(int x)

Write an integer at the current position. The current position is incremented.

Parameters:

x - the value

readInt

public int readInt()

Read an integer at the current position. The current position is incremented.

Returns:

the value

getStringLen

public int getStringLen(java.lang.String s)

Get the length of a String value.

Parameters:

s - the value

Returns:

the length

readString

public java.lang.String readString()

Read a String value. The current position is incremented.

Returns:

the value

writeString

public void writeString(java.lang.String s)

Write a String value. The current position is incremented.

Parameters:

s - the value

fill

public void fill(int len)

Increase the size to the given length. The current position is set to the given value.

Parameters:

len - the new length

create

public static DataPage create(DataHandler handler,
                              int capacity)

Create a new data page for the given handler. The handler will decide what type of buffer is created.

Parameters:

handler - the data handler

capacity - the initial capacity of the buffer

Returns:

the data page

create

public static DataPage create(DataHandler handler,
                              byte[] buff)

Create a new data page using the given data for the given handler. The handler will decide what type of buffer is created.

Parameters:

handler - the data handler

buff - the data

Returns:

the data page

checkCapacity

public void checkCapacity(int plus)

Check if there is still enough capacity in the buffer. This method extends the buffer if required.

Parameters:

plus - the number of additional bytes required

length

public int length()

Get the current write position of this data page, which is the current length.

Returns:

the length

getBytes

public byte[] getBytes()

Get the byte array used for this page.

Returns:

the byte array

reset

public void reset()

Set the position to 0.

writeDataPageNoSize

public void writeDataPageNoSize(DataPage page)

Append the contents of the given data page to this page. The filler is not appended.

Parameters:

page - the page that will be appended

readDataPageNoSize

public DataPage readDataPageNoSize()

Read a data page from this page. The data from the current position to the end of the page is copied.

Returns:

the new page

write

public void write(byte[] buff,
                  int off,
                  int len)

Append a number of bytes to this data page.

Parameters:

buff - the data

off - the offset in the data

len - the length in bytes

read

public void read(byte[] buff,
                 int off,
                 int len)

Copy a number of bytes to the given buffer from the current position. The current position is incremented accordingly.

Parameters:

buff - the output buffer

off - the offset in the output buffer

len - the number of bytes to copy

writeByte

public void writeByte(byte x)

Append one single byte.

Parameters:

x - the value

readByte

public int readByte()

Read one single byte.

Returns:

the value

readLong

public long readLong()

Read a long value. This method reads two int values and combines them.

Returns:

the long value

writeLong

public void writeLong(long x)

Append a long value. This method writes two int values.

Parameters:

x - the value

writeValue

public void writeValue(Value v)
                throws java.sql.SQLException

Append a value.

Parameters:

v - the value

Throws:

java.sql.SQLException

getValueLen

public int getValueLen(Value v)
                throws java.sql.SQLException

Calculate the number of bytes required to encode the given value.

Parameters:

v - the value

Returns:

the number of bytes required to store this value

Throws:

java.sql.SQLException

readValue

public Value readValue()
                throws java.sql.SQLException

Read a value.

Returns:

the value

Throws:

java.sql.SQLException

fillAligned

public void fillAligned()

Fill up the buffer with empty space and an (initially empty) checksum until the size is a multiple of Constants.FILE_BLOCK_SIZE.

setPos

public void setPos(int pos)

Set the current read / write position.

Parameters:

pos - the new position

writeShortInt

public void writeShortInt(int x)

Write a short integer at the current position. The current position is incremented.

Parameters:

x - the value

readShortInt

public int readShortInt()

Read an short integer at the current position. The current position is incremented.

Returns:

the value