com.gc.iotools.stream.is
Class RandomAccessInputStream

java.lang.Object
  java.io.InputStream
      com.gc.iotools.stream.base.AbstractInputStreamWrapper
          com.gc.iotools.stream.is.RandomAccessInputStream

All Implemented Interfaces:

Closeable

public class RandomAccessInputStream
extends AbstractInputStreamWrapper

A RandomAccessInputStream adds functionality to another input stream-namely, the ability to buffer the input, allowing it to be read multiple times, and to support the mark and reset methods.

When the RandomAccessInputStream is created, an internal Store is created. As bytes from the stream are read or skipped, the internal store is refilled as necessary from the source input stream. The implementation of store can be changed to fit the application needs: cache on disk rather than in memory. The default store implementation caches 64K in memory and then write the content on disk.

It also adds the functionality of marking an InputStream without specifying a mark length, thus allowing a reset after an indefinite length of bytes has been read. Check the #mark(int)) javadoc for details.

Since:

1.2.0

Author:

dvd.smnt

See Also:

Store

Field Summary

static int	DEFAULT_DISK_TRHESHOLD Default size for passing from memory allocation to disk allocation for the buffer.
protected long	markLimit
protected long	markPosition
protected long	randomAccessIsPosition Position of read cursor in the RandomAccessInputStream.
protected long	sourcePosition Position of reading in the source stream.

Fields inherited from class com.gc.iotools.stream.base.AbstractInputStreamWrapper

closeCalled, source

Constructor Summary

RandomAccessInputStream(InputStream source)

RandomAccessInputStream(InputStream source, int threshold)
Creates a RandomAccessInputStream with the specified treshold, and saves its argument, the input stream source, for later use.

RandomAccessInputStream(InputStream source, SeekableStore store)

Method Summary

int	available()
protected void	closeOnce()
Store	getStore() Return the underlying store where the cache of data is kept.
protected int	innerRead(byte[] b, int off, int len)
void	mark(int readLimit) Marks the current position in this input stream.
boolean	markSupported() Overrides the markSupported() method of the InputStream class.
void	reset() Repositions this stream to the position at the time the mark method was last called on this input stream.
void	seek(long position) .
void	setStore(Store store)
String	toString() Provides a String representation of the state of the stream for debugging purposes.

Methods inherited from class com.gc.iotools.stream.base.AbstractInputStreamWrapper

close, read, read, skip

Methods inherited from class java.io.InputStream

read

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_DISK_TRHESHOLD

public static final int DEFAULT_DISK_TRHESHOLD

Default size for passing from memory allocation to disk allocation for the buffer.

See Also:

Constant Field Values

sourcePosition

protected long sourcePosition

Position of reading in the source stream.

randomAccessIsPosition

protected long randomAccessIsPosition

Position of read cursor in the RandomAccessInputStream.

markPosition

protected long markPosition

markLimit

protected long markLimit

Constructor Detail

RandomAccessInputStream

public RandomAccessInputStream(InputStream source)

Parameters:

source - The underlying input stream.

RandomAccessInputStream

public RandomAccessInputStream(InputStream source,
                               int threshold)

Creates a RandomAccessInputStream with the specified treshold, and saves its argument, the input stream source, for later use.

When data read under threshold size treshold is kept into memory. Over this size it is placed on disk.

Parameters:

source - The underlying input stream.

threshold - Maximum number of bytes to keep into memory.

See Also:

ThresholdStore

RandomAccessInputStream

public RandomAccessInputStream(InputStream source,
                               SeekableStore store)

Parameters:

source - The underlying input stream.

store -

Method Detail

available

public int available()
              throws IOException

Overrides:

available in class InputStream

Throws:

IOException

getStore

public Store getStore()

Return the underlying store where the cache of data is kept.

Returns:

The underlying store that caches data.

mark

public void mark(int readLimit)

Marks the current position in this input stream. A subsequent call to the reset() method repositions this stream at the last marked position so that subsequent reads re-read the same bytes.

This method extends the original behavior of the class InputStream allowing to use indefinite marking.

• readLimit> 0 The readLimit arguments tells this input stream to allow that many bytes to be read before the mark position gets invalidated.
• readLimit == 0 Invalidate the all the current marks and clean up the temporary files.
• readLimit < 0 Set up an indefinite mark: reset can be invoked regardless on how many bytes have been read.

Overrides:

mark in class InputStream

Parameters:

readLimit - the maximum limit of bytes that can be read before the mark position becomes invalid. If negative allows indefinite marking (the mark never becomes invalid).

See Also:

reset(), InputStream.reset()

markSupported

public boolean markSupported()

Overrides the markSupported() method of the InputStream class.

Overrides:

markSupported in class InputStream

Returns:

Always returns true for this kind of stream.

See Also:

InputStream.markSupported();

reset

public void reset()
           throws IOException

Repositions this stream to the position at the time the mark method was last called on this input stream.

After invoking mark it can be invoked multiple times and it always reset the stream at the previously marked position.

Overrides:

reset in class InputStream

Throws:

IOException - if this stream has not been marked or if the mark has been invalidated.

See Also:

mark(int), InputStream.reset()

seek

public void seek(long position)
          throws IOException

.

Throws:

IOException

setStore

public void setStore(Store store)

toString

public String toString()

Provides a String representation of the state of the stream for debugging purposes.

Overrides:

toString in class Object

Returns:

String that represent the state.

closeOnce

protected void closeOnce()
                  throws IOException

Specified by:

closeOnce in class AbstractInputStreamWrapper

Throws:

IOException

innerRead

protected int innerRead(byte[] b,
                        int off,
                        int len)
                 throws IOException

Specified by:

innerRead in class AbstractInputStreamWrapper

Throws:

IOException