Package org.h2.store.fs.mem

Class FileMemData

java.lang.Object

org.h2.store.fs.mem.FileMemData

class FileMemData
extends java.lang.Object

This class contains the data of an in-memory random access file. Data compression using the LZF algorithm is supported as well.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
(package private) static class	FileMemData.Cache<K,V>	This small cache compresses the data if an element leaves the cache.
(package private) static class	FileMemData.CompressItem	Points to a block of bytes that needs to be compressed.

Field Summary

Fields

Modifier and Type	Field	Description
private static int	BLOCK_SIZE
private static int	BLOCK_SIZE_MASK
private static int	BLOCK_SIZE_SHIFT
private static byte[]	BUFFER
private static int	CACHE_SIZE
private boolean	compress
private static FileMemData.Cache<FileMemData.CompressItem,FileMemData.CompressItem>	COMPRESS_LATER
private static byte[]	COMPRESSED_EMPTY_BLOCK
private java.util.concurrent.atomic.AtomicReference<byte[]>[]	data
private int	id
private boolean	isLockedExclusive
private boolean	isReadOnly
private long	lastModified
private long	length
private static CompressLZF	LZF
private java.lang.String	name
private int	sharedLockCount

Constructor Summary

Constructors

Constructor	Description
FileMemData(java.lang.String name, boolean compress)

Method Summary

Modifier and Type	Method	Description
(package private) boolean	canWrite()	Check whether writing is allowed.
private void	changeLength(long len)
(package private) void	compress(int page)	Compress the data in a byte array.
private void	compressLater(int page)
private byte[]	expand(int page)
(package private) int	getId()
(package private) long	getLastModified()	Get the last modified time.
(package private) java.lang.String	getName()	Get the file name
private byte[]	getPage(int page)	Get the page if it exists.
(package private) long	length()	Get the file length.
(package private) boolean	lockExclusive()	Lock the file in exclusive mode if possible.
(package private) boolean	lockShared()	Lock the file in shared mode if possible.
(package private) long	readWrite(long pos, byte[] b, int off, int len, boolean write)	Read or write.
(package private) void	setName(java.lang.String name)	Set the file name.
private void	setPage(int page, byte[] oldData, byte[] newData, boolean force)	Set the page data.
(package private) boolean	setReadOnly()	Set the read-only flag.
(package private) void	touch(boolean openReadOnly)	Update the last modified time.
(package private) void	truncate(long newLength)	Truncate the file.
(package private) void	unlock()	Unlock the file.

Methods inherited from class java.lang.Object

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

Field Detail

CACHE_SIZE

private static final int CACHE_SIZE

See Also:

Constant Field Values

BLOCK_SIZE_SHIFT

private static final int BLOCK_SIZE_SHIFT

See Also:

Constant Field Values

BLOCK_SIZE

private static final int BLOCK_SIZE

See Also:

Constant Field Values

BLOCK_SIZE_MASK

private static final int BLOCK_SIZE_MASK

See Also:

Constant Field Values

LZF

private static final CompressLZF LZF

BUFFER

private static final byte[] BUFFER

COMPRESSED_EMPTY_BLOCK

private static final byte[] COMPRESSED_EMPTY_BLOCK

COMPRESS_LATER

private static final FileMemData.Cache<FileMemData.CompressItem,FileMemData.CompressItem> COMPRESS_LATER

name

private java.lang.String name

id

private final int id

compress

private final boolean compress

length

private volatile long length

data

private java.util.concurrent.atomic.AtomicReference<byte[]>[] data

lastModified

private long lastModified

isReadOnly

private boolean isReadOnly

isLockedExclusive

private boolean isLockedExclusive

sharedLockCount

private int sharedLockCount

Constructor Detail

FileMemData

FileMemData(java.lang.String name,
            boolean compress)

Method Detail

getPage

private byte[] getPage(int page)

Get the page if it exists.

Parameters:

page - the page id

Returns:

the byte array, or null

setPage

private void setPage(int page,
                     byte[] oldData,
                     byte[] newData,
                     boolean force)

Set the page data.

Parameters:

page - the page id

oldData - the old data

newData - the new data

force - whether the data should be overwritten even if the old data doesn't match

getId

int getId()

lockExclusive

boolean lockExclusive()

Lock the file in exclusive mode if possible.

Returns:

if locking was successful

lockShared

boolean lockShared()

Lock the file in shared mode if possible.

Returns:

if locking was successful

unlock

void unlock()
     throws java.io.IOException

Unlock the file.

Throws:

java.io.IOException

compressLater

private void compressLater(int page)

expand

private byte[] expand(int page)

compress

void compress(int page)

Compress the data in a byte array.

Parameters:

page - which page to compress

touch

void touch(boolean openReadOnly)

Update the last modified time.

Parameters:

openReadOnly - if the file was opened in read-only mode

length

long length()

Get the file length.

Returns:

the length

truncate

void truncate(long newLength)

Truncate the file.

Parameters:

newLength - the new length

changeLength

private void changeLength(long len)

readWrite

long readWrite(long pos,
               byte[] b,
               int off,
               int len,
               boolean write)

Read or write.

Parameters:

pos - the position

b - the byte array

off - the offset within the byte array

len - the number of bytes

write - true for writing

Returns:

the new position

setName

void setName(java.lang.String name)

Set the file name.

Parameters:

name - the name

getName

java.lang.String getName()

Get the file name

Returns:

the name

getLastModified

long getLastModified()

Get the last modified time.

Returns:

the time

canWrite

boolean canWrite()

Check whether writing is allowed.

Returns:

true if it is

setReadOnly

boolean setReadOnly()

Set the read-only flag.

Returns:

true