Package com.healthmarketscience.jackcess.util

Class MemFileChannel

java.lang.Object

java.nio.channels.spi.AbstractInterruptibleChannel

java.nio.channels.FileChannel

com.healthmarketscience.jackcess.util.MemFileChannel

All Implemented Interfaces:

Closeable, AutoCloseable, ByteChannel, Channel, GatheringByteChannel, InterruptibleChannel, ReadableByteChannel, ScatteringByteChannel, SeekableByteChannel, WritableByteChannel

public class MemFileChannel
extends FileChannel

FileChannel implementation which maintains the entire "file" in memory. This enables working with a Database entirely in memory (for situations where disk usage may not be possible or desirable). Obviously, this requires enough jvm heap space to fit the file data. Use one of the newChannel() methods to construct an instance of this class.

In order to use this class with a Database, you must use the DatabaseBuilder to open/create the Database instance, passing an instance of this class to the DatabaseBuilder.setChannel(java.nio.channels.FileChannel) method.

Implementation note: this class is optimized for use with Database. Therefore not all methods may be implemented and individual read/write operations are only supported within page boundaries.

Author:

James Ahlborn

Usage:

Advanced: This class is for advanced/internal use.

Nested Class Summary

Nested classes/interfaces inherited from class java.nio.channels.FileChannel

FileChannel.MapMode

Field Summary

Fields

Modifier and Type	Field	Description
static String	RO_CHANNEL_MODE	read-only channel access mode
static String	RW_CHANNEL_MODE	read/write channel access mode

Method Summary

Modifier and Type	Method	Description
void	force(boolean metaData)
FileLock	lock(long position, long size, boolean shared)
MappedByteBuffer	map(FileChannel.MapMode mode, long position, long size)
static MemFileChannel	newChannel()	Creates a new read/write, empty MemFileChannel.
static MemFileChannel	newChannel(File file)	Creates a new read/write MemFileChannel containing the contents of the given File.
static MemFileChannel	newChannel(File file, String mode)	Creates a new MemFileChannel containing the contents of the given File with the given mode (for mode details see RandomAccessFile(File,String)).
static MemFileChannel	newChannel(InputStream in)	Creates a new read/write MemFileChannel containing the contents of the given InputStream.
static MemFileChannel	newChannel(InputStream in, String mode)	Creates a new MemFileChannel containing the contents of the given InputStream with the given mode (for mode details see RandomAccessFile(File,String)).
static MemFileChannel	newChannel(ReadableByteChannel in)	Creates a new read/write MemFileChannel containing the contents of the given ReadableByteChannel.
static MemFileChannel	newChannel(ReadableByteChannel in, String mode)	Creates a new MemFileChannel containing the contents of the given ReadableByteChannel with the given mode (for mode details see RandomAccessFile(File,String)).
static MemFileChannel	newChannel(Path file)	Creates a new read/write MemFileChannel containing the contents of the given Path.
static MemFileChannel	newChannel(Path file, OpenOption... opts)	Creates a new MemFileChannel containing the contents of the given Path with the given mode (for mode details see RandomAccessFile(File,String)).
long	position()
FileChannel	position(long newPosition)
int	read(ByteBuffer dst)
long	read(ByteBuffer[] dsts, int offset, int length)
int	read(ByteBuffer dst, long position)
long	size()
long	transferFrom(ReadableByteChannel src, long position, long count)
long	transferTo(long position, long count, OutputStream dst)	Convenience method for writing the selected portion of this channel to the given destination stream.
long	transferTo(long position, long count, WritableByteChannel dst)
long	transferTo(OutputStream dst)	Convenience method for writing the entire contents of this channel to the given destination stream.
long	transferTo(WritableByteChannel dst)	Convenience method for writing the entire contents of this channel to the given destination channel.
FileChannel	truncate(long newSize)
FileLock	tryLock(long position, long size, boolean shared)
int	write(ByteBuffer src)
long	write(ByteBuffer[] srcs, int offset, int length)
int	write(ByteBuffer src, long position)

Methods inherited from class java.nio.channels.FileChannel

lock, open, open, read, tryLock, write

Methods inherited from class java.nio.channels.spi.AbstractInterruptibleChannel

close, isOpen

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.nio.channels.Channel

isOpen

Field Detail

RO_CHANNEL_MODE

public static final String RO_CHANNEL_MODE

read-only channel access mode

See Also:

Constant Field Values

RW_CHANNEL_MODE

public static final String RW_CHANNEL_MODE

read/write channel access mode

See Also:

Constant Field Values

Method Detail

newChannel

public static MemFileChannel newChannel()

Creates a new read/write, empty MemFileChannel.

newChannel

public static MemFileChannel newChannel(File file)
                                 throws IOException

Creates a new read/write MemFileChannel containing the contents of the given File. Note, modifications to the returned channel will not affect the original File source.

Throws:

IOException

newChannel

public static MemFileChannel newChannel(File file,
                                        String mode)
                                 throws IOException

Creates a new MemFileChannel containing the contents of the given File with the given mode (for mode details see RandomAccessFile(File,String)). Note, modifications to the returned channel will not affect the original File source.

Throws:

IOException

newChannel

public static MemFileChannel newChannel(Path file,
                                        OpenOption... opts)
                                 throws IOException

Creates a new MemFileChannel containing the contents of the given Path with the given mode (for mode details see RandomAccessFile(File,String)). Note, modifications to the returned channel will not affect the original File source.

Throws:

IOException

newChannel

public static MemFileChannel newChannel(Path file)
                                 throws IOException

Creates a new read/write MemFileChannel containing the contents of the given Path. Note, modifications to the returned channel will not affect the original File source.

Throws:

IOException

newChannel

public static MemFileChannel newChannel(InputStream in)
                                 throws IOException

Creates a new read/write MemFileChannel containing the contents of the given InputStream.

Throws:

IOException

newChannel

public static MemFileChannel newChannel(InputStream in,
                                        String mode)
                                 throws IOException

Creates a new MemFileChannel containing the contents of the given InputStream with the given mode (for mode details see RandomAccessFile(File,String)).

Throws:

IOException

newChannel

public static MemFileChannel newChannel(ReadableByteChannel in)
                                 throws IOException

Creates a new read/write MemFileChannel containing the contents of the given ReadableByteChannel.

Throws:

IOException

newChannel

public static MemFileChannel newChannel(ReadableByteChannel in,
                                        String mode)
                                 throws IOException

Creates a new MemFileChannel containing the contents of the given ReadableByteChannel with the given mode (for mode details see RandomAccessFile(File,String)).

Throws:

IOException

read

public int read(ByteBuffer dst)

Specified by:

read in interface ReadableByteChannel

Specified by:

read in interface SeekableByteChannel

Specified by:

read in class FileChannel

read

public int read(ByteBuffer dst,
                long position)

Specified by:

read in class FileChannel

write

public int write(ByteBuffer src)

Specified by:

write in interface SeekableByteChannel

Specified by:

write in interface WritableByteChannel

Specified by:

write in class FileChannel

write

public int write(ByteBuffer src,
                 long position)

Specified by:

write in class FileChannel

position

public long position()

Specified by:

position in interface SeekableByteChannel

Specified by:

position in class FileChannel

position

public FileChannel position(long newPosition)

Specified by:

position in interface SeekableByteChannel

Specified by:

position in class FileChannel

size

public long size()

Specified by:

size in interface SeekableByteChannel

Specified by:

size in class FileChannel

truncate

public FileChannel truncate(long newSize)

Specified by:

truncate in interface SeekableByteChannel

Specified by:

truncate in class FileChannel

force

public void force(boolean metaData)

Specified by:

force in class FileChannel

transferTo

public long transferTo(WritableByteChannel dst)
                throws IOException

Convenience method for writing the entire contents of this channel to the given destination channel.

Throws:

IOException

See Also:

transferTo(long,long,WritableByteChannel)

transferTo

public long transferTo(long position,
                       long count,
                       WritableByteChannel dst)
                throws IOException

Specified by:

transferTo in class FileChannel

Throws:

IOException

transferTo

public long transferTo(OutputStream dst)
                throws IOException

Convenience method for writing the entire contents of this channel to the given destination stream.

Throws:

IOException

See Also:

transferTo(long,long,WritableByteChannel)

transferTo

public long transferTo(long position,
                       long count,
                       OutputStream dst)
                throws IOException

Convenience method for writing the selected portion of this channel to the given destination stream.

Throws:

IOException

See Also:

transferTo(long,long,WritableByteChannel)

transferFrom

public long transferFrom(ReadableByteChannel src,
                         long position,
                         long count)
                  throws IOException

Specified by:

transferFrom in class FileChannel

Throws:

IOException

write

public long write(ByteBuffer[] srcs,
                  int offset,
                  int length)

Specified by:

write in interface GatheringByteChannel

Specified by:

write in class FileChannel

read

public long read(ByteBuffer[] dsts,
                 int offset,
                 int length)

Specified by:

read in interface ScatteringByteChannel

Specified by:

read in class FileChannel

map

public MappedByteBuffer map(FileChannel.MapMode mode,
                            long position,
                            long size)

Specified by:

map in class FileChannel

lock

public FileLock lock(long position,
                     long size,
                     boolean shared)

Specified by:

lock in class FileChannel

tryLock

public FileLock tryLock(long position,
                        long size,
                        boolean shared)

Specified by:

tryLock in class FileChannel