org.h2.store
Class Data

java.lang.Object
  org.h2.store.Data

public class Data
extends java.lang.Object

This class represents a byte buffer that contains persistent data of a page.

Field Summary

protected byte[]	data The data itself.
static int	LENGTH_INT The length of an integer value.

Constructor Summary

protected

Data(DataHandler handler, byte[] data)

Method Summary

void	checkCapacity(int plus) Check if there is still enough capacity in the buffer.
static Data	create(DataHandler handler, byte[] buff) Create a new buffer using the given data for the given handler.
static Data	create(DataHandler handler, int capacity) Create a new buffer 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.
static int	getStringLen(java.lang.String s) Get the length of a String.
static int	getStringWithoutLengthLen(java.lang.String s, int len) Calculate the length of String, excluding the bytes required to encode the length.
int	getValueLen(Value v) Calculate the number of bytes required to encode the given value.
static int	getValueLen(Value v, DataHandler handler) Calculate the number of bytes required to encode the given value.
static int	getVarIntLen(int x) The number of bytes required for a variable size int.
static int	getVarLongLen(long x) The number of bytes required for a variable size long.
int	length() Get the current write position of this buffer, which is the current length.
void	read(byte[] buff) Copy a number of bytes to the given buffer from the current position.
void	read(byte[] buff, int off, int len) Copy a number of bytes to the given buffer from the current position.
byte	readByte() Read one single byte.
int	readInt() Read an integer at the current position.
long	readLong() Read a long value.
short	readShortInt() Read an short integer at the current position.
java.lang.String	readString() Read a String value.
Value	readValue() Read a value.
int	readVarInt() Read a variable size int.
long	readVarLong() Read a variable size long.
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	truncate(int size) Shrink the array to this size.
void	write(byte[] buff) Append a number of bytes to this buffer.
void	write(byte[] buff, int off, int len) Append a number of bytes to this buffer.
void	writeByte(byte x) Append one single byte.
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.
void	writeValue(Value v) Append a value.
void	writeVarInt(int x) Write a variable size int.
void	writeVarLong(long x) Write a variable size long.

Methods inherited from class java.lang.Object

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

Field Detail

LENGTH_INT

public static final int LENGTH_INT

The length of an integer value.

See Also:

Constant Field Values

data

protected byte[] data

The data itself.

Constructor Detail

Data

protected Data(DataHandler handler,
               byte[] data)

Method Detail

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 static int getStringLen(java.lang.String s)

Get the length of a String. This includes the bytes required to encode the length.

Parameters:

s - the string

Returns:

the number of bytes required

getStringWithoutLengthLen

public static int getStringWithoutLengthLen(java.lang.String s,
                                            int len)

Calculate the length of String, excluding the bytes required to encode the length.

For performance reasons the internal representation of a String is similar to UTF-8, but not exactly UTF-8.

Parameters:

s - the string

len - the length of the string

Returns:

the number of bytes required

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. 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 Data create(DataHandler handler,
                          int capacity)

Create a new buffer 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 buffer

create

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

Create a new buffer 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 buffer

length

public int length()

Get the current write position of this buffer, 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.

write

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

Append a number of bytes to this buffer.

Parameters:

buff - the data

off - the offset in the data

len - the length in bytes

write

public void write(byte[] buff)

Append a number of bytes to this buffer.

Parameters:

buff - the data

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

read

public void read(byte[] buff)

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

Parameters:

buff - the output buffer

writeByte

public void writeByte(byte x)

Append one single byte.

Parameters:

x - the value

readByte

public byte 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)

Append a value.

Parameters:

v - the value

readValue

public Value readValue()

Read a value.

Returns:

the value

getValueLen

public int getValueLen(Value v)

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

getValueLen

public static int getValueLen(Value v,
                              DataHandler handler)

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

Parameters:

v - the value

handler - the data handler for lobs

Returns:

the number of bytes required to store this value

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 short readShortInt()

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

Returns:

the value

truncate

public void truncate(int size)

Shrink the array to this size.

Parameters:

size - the new size

getVarIntLen

public static int getVarIntLen(int x)

The number of bytes required for a variable size int.

Parameters:

x - the value

Returns:

the len

writeVarInt

public void writeVarInt(int x)

Write a variable size int.

Parameters:

x - the value

readVarInt

public int readVarInt()

Read a variable size int.

Returns:

the value

getVarLongLen

public static int getVarLongLen(long x)

The number of bytes required for a variable size long.

Parameters:

x - the value

Returns:

the len

writeVarLong

public void writeVarLong(long x)

Write a variable size long.

Parameters:

x - the value

readVarLong

public long readVarLong()

Read a variable size long.

Returns:

the value

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

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.