net.sf.jasperreports.engine.util
Class JRSwapFile

java.lang.Object
  net.sf.jasperreports.engine.util.JRSwapFile

Direct Known Subclasses:

JRConcurrentSwapFile

public class JRSwapFile
extends java.lang.Object

Swap file implementation that can be used as a disk cache for arbitrary binary data.

Fixed-size blocks are allocated inside the swap file when a caller wants to write data. The caller receives a handle to the allocated area based on which it can read the data or free the area.

The implementation is thread-safe. I/O operations are performed in synchronized blocks, only one thread would do a read or write at one moment.

Version:

$Id: JRSwapFile.java 5180 2012-03-29 13:23:12Z teodord $

Author:

Lucian Chirita (lucianc@users.sourceforge.net)

Nested Class Summary

protected static class	JRSwapFile.LongQueue
static class	JRSwapFile.SwapHandle

Field Summary

protected java.io.RandomAccessFile	file
static java.lang.String	PROPERTY_DELETE_ON_EXIT Property that instructs whether deleteOnExit is to be requested for swap files.

Constructor Summary

JRSwapFile(java.lang.String directory, int blockSize, int minGrowCount)
Creates a swap file.

Method Summary

void	dispose() Closes and deletes the swap file.
protected void	finalize()
void	free(JRSwapFile.SwapHandle handle) Frees an allocated area.
protected void	freeBlocks(long[] offsets)
protected void	read(byte[] data, int dataOffset, int dataLength, long fileOffset)
byte[]	read(JRSwapFile.SwapHandle handle, boolean free) Reads all the data from an allocated area.
protected long[]	reserveFreeBlocks(int blockCount)
JRSwapFile.SwapHandle	write(byte[] data) Allocates an area in the swap file and writes data in it.
protected void	write(byte[] data, int dataSize, int dataOffset, long fileOffset)

Methods inherited from class java.lang.Object

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

Field Detail

PROPERTY_DELETE_ON_EXIT

public static final java.lang.String PROPERTY_DELETE_ON_EXIT

Property that instructs whether deleteOnExit is to be requested for swap files. Swap files are explicitly deleted on dispose() and garbage collection.

See Also:

Constant Field Values

file

protected final java.io.RandomAccessFile file

Constructor Detail

JRSwapFile

public JRSwapFile(java.lang.String directory,
                  int blockSize,
                  int minGrowCount)

Creates a swap file. The file name is generated automatically.

Parameters:

directory - the directory where the file should be created.

blockSize - the size of the blocks allocated by the swap file

minGrowCount - the minimum number of blocks by which the swap file grows when full

Method Detail

write

public JRSwapFile.SwapHandle write(byte[] data)
                            throws java.io.IOException

Allocates an area in the swap file and writes data in it.

Parameters:

data - the data for which to allocate an area in the file

Returns:

a handle to the allocated area

Throws:

java.io.IOException

write

protected void write(byte[] data,
                     int dataSize,
                     int dataOffset,
                     long fileOffset)
              throws java.io.IOException

Throws:

java.io.IOException

read

public byte[] read(JRSwapFile.SwapHandle handle,
                   boolean free)
            throws java.io.IOException

Reads all the data from an allocated area.

Parameters:

handle - the allocated area handle

free - whether to free the area after reading

Returns:

the whole data saved in an allocated area

Throws:

java.io.IOException

read

protected void read(byte[] data,
                    int dataOffset,
                    int dataLength,
                    long fileOffset)
             throws java.io.IOException

Throws:

java.io.IOException

free

public void free(JRSwapFile.SwapHandle handle)

Frees an allocated area.

Parameters:

handle - the allocated area handle

dispose

public void dispose()

Closes and deletes the swap file.

finalize

protected void finalize()
                 throws java.lang.Throwable

Overrides:

finalize in class java.lang.Object

Throws:

java.lang.Throwable

reserveFreeBlocks

protected long[] reserveFreeBlocks(int blockCount)
                            throws java.io.IOException

Throws:

java.io.IOException

freeBlocks

protected void freeBlocks(long[] offsets)