de.waldheinz.fs.util
Class RamDisk

java.lang.Object
  de.waldheinz.fs.util.RamDisk

All Implemented Interfaces:

BlockDevice

public final class RamDisk
extends Object
implements BlockDevice

A BlockDevice that lives entirely in heap memory. This is basically a RAM disk. A RamDisk is always writable.

Author:

Matthias Treydte <waldheinz at gmail.com>

Field Summary

static int

DEFAULT_SECTOR_SIZE The default sector size for RamDisks.

Constructor Summary

RamDisk(int size)
Creates a new instance of RamDisk of this specified size and using the DEFAULT_SECTOR_SIZE.

RamDisk(int size, int sectorSize)
Creates a new instance of RamDisk of this specified size and sector size

Method Summary

void	close() Closes this BlockDevice.
void	flush() Flushes data in caches to the actual storage.
ByteBuffer	getBuffer() Returns a slice of the ByteBuffer that is used by this RamDisk as it's backing store.
int	getSectorSize() Returns the size of a sector on this device.
long	getSize() Gets the total length of this device in bytes.
boolean	isClosed() Checks if this device was already closed.
boolean	isReadOnly() Returns always false, as a RamDisk is always writable.
void	read(long devOffset, ByteBuffer dest) Read a block of data from this device.
static RamDisk	readGzipped(File f) Reads a GZIP compressed file into a new RamDisk instance.
static RamDisk	readGzipped(InputStream in) Reads a GZIP compressed disk image from the specified input stream and returns a RamDisk holding the decompressed image.
void	write(long devOffset, ByteBuffer src) Writes a block of data to this device.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_SECTOR_SIZE

public static final int DEFAULT_SECTOR_SIZE

The default sector size for RamDisks.

See Also:

Constant Field Values

Constructor Detail

RamDisk

public RamDisk(int size)

Creates a new instance of RamDisk of this specified size and using the DEFAULT_SECTOR_SIZE.

Parameters:

size - the size of the new block device

RamDisk

public RamDisk(int size,
               int sectorSize)

Creates a new instance of RamDisk of this specified size and sector size

Parameters:

size - the size of the new block device

sectorSize - the sector size of the new block device

Method Detail

readGzipped

public static RamDisk readGzipped(InputStream in)
                           throws IOException

Reads a GZIP compressed disk image from the specified input stream and returns a RamDisk holding the decompressed image.

Parameters:

in - the stream to read the disk image from

Returns:

the decompressed RamDisk

Throws:

IOException - on read or decompression error

readGzipped

public static RamDisk readGzipped(File f)
                           throws FileNotFoundException,
                                  IOException

Reads a GZIP compressed file into a new RamDisk instance.

Parameters:

f - the file to read

Returns:

the new RamDisk with the file contents

Throws:

FileNotFoundException - if the specified file does not exist

IOException - on read error

getSize

public long getSize()

Description copied from interface: BlockDevice

Gets the total length of this device in bytes.

Specified by:

getSize in interface BlockDevice

Returns:

the total number of bytes on this device

read

public void read(long devOffset,
                 ByteBuffer dest)
          throws IOException

Description copied from interface: BlockDevice

Read a block of data from this device.

Specified by:

read in interface BlockDevice

Parameters:

devOffset - the byte offset where to read the data from

dest - the destination buffer where to store the data read

Throws:

IOException - on read error

write

public void write(long devOffset,
                  ByteBuffer src)
           throws IOException

Description copied from interface: BlockDevice

Writes a block of data to this device.

Specified by:

write in interface BlockDevice

Parameters:

devOffset - the byte offset where to store the data

src - the source ByteBuffer to write to the device

Throws:

IOException - on write error

See Also:

BlockDevice.isReadOnly()

getBuffer

public ByteBuffer getBuffer()

Returns a slice of the ByteBuffer that is used by this RamDisk as it's backing store. The returned buffer will be live (reflecting any changes made through the method, but read-only.

Returns:

a buffer holding the contents of this RamDisk

flush

public void flush()
           throws IOException

Description copied from interface: BlockDevice

Flushes data in caches to the actual storage.

Specified by:

flush in interface BlockDevice

Throws:

IOException - on write error

getSectorSize

public int getSectorSize()

Description copied from interface: BlockDevice

Returns the size of a sector on this device.

Specified by:

getSectorSize in interface BlockDevice

Returns:

the sector size in bytes

close

public void close()
           throws IOException

Description copied from interface: BlockDevice

Closes this BlockDevice. No methods of this device may be accesses after this method was called.

Specified by:

close in interface BlockDevice

Throws:

IOException - on error closing this device

See Also:

BlockDevice.isClosed()

isClosed

public boolean isClosed()

Description copied from interface: BlockDevice

Checks if this device was already closed. No methods may be called on a closed device (except this method).

Specified by:

isClosed in interface BlockDevice

Returns:

if this device is closed

isReadOnly

public boolean isReadOnly()

Returns always false, as a RamDisk is always writable.

Specified by:

isReadOnly in interface BlockDevice

Returns:

always false