org.mapdb

Class Volume

java.lang.Object

org.mapdb.Volume

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

Direct Known Subclasses:

Volume.ByteArrayVol, Volume.ByteBufferVol, Volume.ByteBufferVolSingle, Volume.FileChannelVol, Volume.RandomAccessFileVol, Volume.ReadOnly, Volume.SingleByteArrayVol

public abstract class Volume
extends java.lang.Object
implements java.io.Closeable

MapDB abstraction over raw storage (file, disk partition, memory etc...).

Implementations needs to be thread safe (especially 'ensureAvailable') operation. However updates do not have to be atomic, it is clients responsibility to ensure two threads are not writing/reading into the same location.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Volume.ByteArrayVol
static class	Volume.ByteBufferVol Abstract Volume over bunch of ByteBuffers It leaves ByteBufferVol details (allocation, disposal) on subclasses.
static class	Volume.ByteBufferVolSingle Abstract Volume over single ByteBuffer, maximal size is 2GB (32bit limit).
static class	Volume.FileChannelVol Volume which uses FileChannel.
static class	Volume.MappedFileVol
static class	Volume.MappedFileVolSingle
static class	Volume.MemoryVol
static class	Volume.MemoryVolSingle
static class	Volume.RandomAccessFileVol
static class	Volume.ReadOnly
static class	Volume.SingleByteArrayVol Volume backed by on-heap byte[] with maximal fixed size 2GB.
static class	Volume.VolumeFactory

Field Summary

Fields

Modifier and Type	Field and Description
static Volume.VolumeFactory	UNSAFE_VOL_FACTORY If sun.misc.Unsafe is available it will use Volume based on Unsafe.

Constructor Summary

Constructors

Constructor and Description
Volume()

Method Summary

Modifier and Type	Method and Description
abstract void	clear(long startOffset, long endOffset) Set all bytes between startOffset and endOffset to zero.
abstract void	close()
void	copyEntireVolumeTo(Volume to) Copy content of this volume to another.
void	deleteFile()
abstract void	ensureAvailable(long offset) Check space allocated by Volume is bigger or equal to given offset.
boolean	fileLoad() If underlying storage is memory-mapped-file, this method will try to load and precache all file data into disk cache.
abstract byte	getByte(long offset)
abstract void	getData(long offset, byte[] bytes, int bytesPos, int size)
abstract java.io.DataInput	getDataInput(long offset, int size)
java.io.DataInput	getDataInputOverlap(long offset, int size)
abstract java.io.File	getFile() returns underlying file if it exists
abstract boolean	getFileLocked() return true if this Volume holds exclusive lock over its file
abstract int	getInt(long offset)
abstract long	getLong(long offset)
long	getLongPackBidi(long offset)
long	getLongPackBidiReverse(long offset)
long	getPackedLong(long position) Unpack long value from the Volume.
long	getSixLong(long pos)
int	getUnsignedByte(long offset)
int	getUnsignedShort(long offset)
long	hash(long off, long len, long seed) Calculates XXHash64 from this Volume content.
boolean	isClosed()
abstract boolean	isSliced()
abstract long	length()
abstract void	putByte(long offset, byte value)
abstract void	putData(long offset, byte[] src, int srcPos, int srcSize)
abstract void	putData(long offset, java.nio.ByteBuffer buf)
void	putDataOverlap(long offset, byte[] src, int srcPos, int srcSize)
abstract void	putInt(long offset, int value)
abstract void	putLong(long offset, long value)
int	putLongPackBidi(long offset, long value)
int	putPackedLong(long pos, long value) Put packed long at given position.
void	putSixLong(long pos, long value)
void	putUnsignedByte(long offset, int b)
void	putUnsignedShort(long offset, int value)
abstract int	sliceSize()
abstract void	sync()
void	transferInto(long inputOffset, Volume target, long targetOffset, long size) Transfers data from this Volume into target volume.
abstract void	truncate(long size)
static void	volumeTransfer(long size, Volume from, Volume to) transfer data from one volume to second.

Methods inherited from class java.lang.Object

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

Field Detail

UNSAFE_VOL_FACTORY

public static final Volume.VolumeFactory UNSAFE_VOL_FACTORY

If sun.misc.Unsafe is available it will use Volume based on Unsafe. If Unsafe is not available for some reason (Android), use DirectByteBuffer instead.

Constructor Detail

Volume

public Volume()

Method Detail

fileLoad

public boolean fileLoad()

If underlying storage is memory-mapped-file, this method will try to load and precache all file data into disk cache. Most likely it will call MappedByteBuffer.load(), but could also read content of entire file etc This method will not pin data into memory, they might be removed at any time.

Returns:

true if this method did something, false if underlying storage does not support loading

isClosed

public boolean isClosed()

ensureAvailable

public abstract void ensureAvailable(long offset)

Check space allocated by Volume is bigger or equal to given offset. So it is safe to write into smaller offsets.

Parameters:

offset -

truncate

public abstract void truncate(long size)

putLong

public abstract void putLong(long offset,
                             long value)

putInt

public abstract void putInt(long offset,
                            int value)

putByte

public abstract void putByte(long offset,
                             byte value)

putData

public abstract void putData(long offset,
                             byte[] src,
                             int srcPos,
                             int srcSize)

putData

public abstract void putData(long offset,
                             java.nio.ByteBuffer buf)

putDataOverlap

public void putDataOverlap(long offset,
                           byte[] src,
                           int srcPos,
                           int srcSize)

getLong

public abstract long getLong(long offset)

getInt

public abstract int getInt(long offset)

getByte

public abstract byte getByte(long offset)

getDataInput

public abstract java.io.DataInput getDataInput(long offset,
                                               int size)

getDataInputOverlap

public java.io.DataInput getDataInputOverlap(long offset,
                                             int size)

getData

public abstract void getData(long offset,
                             byte[] bytes,
                             int bytesPos,
                             int size)

close

public abstract void close()

Specified by:

close in interface java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable

sync

public abstract void sync()

sliceSize

public abstract int sliceSize()

Returns:

slice size or -1 if not sliced

deleteFile

public void deleteFile()

isSliced

public abstract boolean isSliced()

length

public abstract long length()

putUnsignedShort

public void putUnsignedShort(long offset,
                             int value)

getUnsignedShort

public int getUnsignedShort(long offset)

getUnsignedByte

public int getUnsignedByte(long offset)

putUnsignedByte

public void putUnsignedByte(long offset,
                            int b)

putLongPackBidi

public int putLongPackBidi(long offset,
                           long value)

getLongPackBidi

public long getLongPackBidi(long offset)

getLongPackBidiReverse

public long getLongPackBidiReverse(long offset)

getSixLong

public long getSixLong(long pos)

putSixLong

public void putSixLong(long pos,
                       long value)

putPackedLong

public int putPackedLong(long pos,
                         long value)

Put packed long at given position.

Parameters:

value - to be written

Returns:

number of bytes consumed by packed value

getPackedLong

public long getPackedLong(long position)

Unpack long value from the Volume. Highest 4 bits reused to indicate number of bytes read from Volume. One can use result & DataIO.PACK_LONG_RESULT_MASK to remove size;

Parameters:

position - to read value from

Returns:

The long value, minus highest byte

getFile

public abstract java.io.File getFile()

returns underlying file if it exists

getFileLocked

public abstract boolean getFileLocked()

return true if this Volume holds exclusive lock over its file

transferInto

public void transferInto(long inputOffset,
                         Volume target,
                         long targetOffset,
                         long size)

Transfers data from this Volume into target volume. If its possible, the implementation should override this method to enable direct memory transfer. Caller must respect slice boundaries. ie it is not possible to transfer data which cross slice boundaries.

Parameters:

inputOffset - offset inside this Volume, ie data will be read from this offset

target - Volume to copy data into

targetOffset - position in target volume where data will be copied into

size - size of data to copy

clear

public abstract void clear(long startOffset,
                           long endOffset)

Set all bytes between startOffset and endOffset to zero. Area between offsets must be ready for write once clear finishes.

copyEntireVolumeTo

public void copyEntireVolumeTo(Volume to)

Copy content of this volume to another. Target volume might grow, but is never shrank. Target is also not synced

hash

public long hash(long off,
                 long len,
                 long seed)

Calculates XXHash64 from this Volume content.

This code comes from LZ4-Java created by Adrien Grand.

Parameters:

off - offset to start calculation from

len - length of data to calculate hash

seed - hash seed

Returns:

XXHash.

volumeTransfer

public static void volumeTransfer(long size,
                                  Volume from,
                                  Volume to)

transfer data from one volume to second. Second volume will be expanded if needed