net.sf.jasperreports.engine.util

Class JRSwapFile

java.lang.Object

net.sf.jasperreports.engine.util.JRSwapFile

Direct Known Subclasses:

JRConcurrentSwapFile

public class JRSwapFile
extends 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

Nested Classes

Modifier and Type	Class and Description
protected static class	JRSwapFile.LongQueue
static class	JRSwapFile.SwapHandle

Field Summary

Fields

Modifier and Type	Field and Description
protected RandomAccessFile	file
static String	PROPERTY_DELETE_ON_EXIT Property that instructs whether deleteOnExit is to be requested for swap files.

Constructor Summary

Constructors

Constructor and Description
JRSwapFile(String directory, int blockSize, int minGrowCount) Creates a swap file.

Method Summary

Methods

Modifier and Type	Method and Description
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 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 RandomAccessFile file

Constructor Detail

JRSwapFile

public JRSwapFile(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 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:

IOException

write

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

Throws:

IOException

read

public byte[] read(JRSwapFile.SwapHandle handle,
          boolean free)
            throws 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:

IOException

read

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

Throws:

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 Throwable

Overrides:

finalize in class Object

Throws:

Throwable

reserveFreeBlocks

protected long[] reserveFreeBlocks(int blockCount)
                            throws IOException

Throws:

IOException

freeBlocks

protected void freeBlocks(long[] offsets)