Package it.unimi.dsi.fastutil.io

Class InspectableFileCachedInputStream

java.lang.Object

java.io.InputStream

it.unimi.dsi.fastutil.io.MeasurableInputStream

it.unimi.dsi.fastutil.io.InspectableFileCachedInputStream

All Implemented Interfaces:

MeasurableStream, RepositionableStream, Closeable, AutoCloseable, Channel, WritableByteChannel

public class InspectableFileCachedInputStream
extends MeasurableInputStream
implements RepositionableStream, WritableByteChannel

A repositionable MeasurableInputStream based on cached data received by a WritableByteChannel whose first bytes can be inspected directly.

An instance of this class acts as a buffer holding the bytes written through its WritableByteChannel interface (which can be easily turned into an OutputStream using Channels.newOutputStream(WritableByteChannel)). The data can be discarded at any time using clear(). The first inspectable bytes of buffer contains the first bytes written. When buffer is full, the bytes are written to an overflow file.

At any time, the stream of bytes written since creation (or since the last clear()) are available as a fully implemented MeasurableInputStream which also implements RepositionableStream and supports marking. Note that you must arbitrate carefully write and read accesses, as it is always possible to call write(ByteBuffer) and thus modify the length of the MeasurableInputStream.

The method close() makes the MeasurableInputStream and WritableByteChannel state-changing methods temporarily throw an IOException, but does not otherwise modify the state of the stream. You can reopen the stream later, or clear it. The method dispose() can be used to release the resources associated with the stream.

Buffering

This class provides no form of buffering except for the memory buffer described above, both when reading and when writing. Users should consider wrapping instances of this class with a FastBufferedInputStream, as reads after the buffer has been exhausted will be performed directly on a RandomAccessFile.

Field Summary

Fields

Modifier and Type	Field	Description
byte[]	buffer	The inspection buffer.
static boolean	DEBUG
static int	DEFAULT_BUFFER_SIZE	The default buffer size (64KiB).
int	inspectable	The number of valid bytes currently in buffer.

Constructor Summary

Constructors

Constructor	Description
InspectableFileCachedInputStream()	Creates a new instance with default buffer size and overflow-file directory.
InspectableFileCachedInputStream(int bufferSize)	Creates a new instance with specified buffer size and default overflow-file directory.
InspectableFileCachedInputStream(int bufferSize, File overflowFile)	Creates a new instance with specified buffer size and overlow-file directory.

Method Summary

Modifier and Type	Method	Description
int	available()
void	clear()	Clears the content of this InspectableFileCachedInputStream, zeroing the length of the represented stream.
void	close()	Makes the stream unreadable until the next clear().
void	dispose()	Disposes this stream, deleting the overflow file.
boolean	isOpen()
long	length()	Returns the overall length of this stream (optional operation).
void	mark(int readlimit)
boolean	markSupported()
long	position()	Returns the current stream position.
void	position(long position)	Positions the input stream.
int	read()
int	read(byte[] b)
int	read(byte[] b, int offset, int length)
void	reopen()	Makes the stream readable again after a close().
void	reset()
long	skip(long n)
void	truncate(long size)	Truncates the overflow file to a given size if possible.
int	write(ByteBuffer byteBuffer)	Appends the content of a specified buffer to the end of the currently represented stream.

Methods inherited from class java.io.InputStream

nullInputStream, readAllBytes, readNBytes, readNBytes, skipNBytes, transferTo

Methods inherited from class java.lang.Object

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

Field Detail

DEBUG

public static final boolean DEBUG

See Also:

Constant Field Values

DEFAULT_BUFFER_SIZE

public static final int DEFAULT_BUFFER_SIZE

The default buffer size (64KiB).

See Also:

Constant Field Values

buffer

public final byte[] buffer

The inspection buffer. The first inspectable bytes contain the first part of the input stream. The buffer is available for inspection, but users should not modify its content.

inspectable

public int inspectable

The number of valid bytes currently in buffer.

Constructor Detail

InspectableFileCachedInputStream

public InspectableFileCachedInputStream(int bufferSize,
                                        File overflowFile)
                                 throws IOException

Creates a new instance with specified buffer size and overlow-file directory.

Parameters:

bufferSize - the buffer size, in bytes.

overflowFile - the directory where the overflow file should be created, or null for the default temporary directory.

Throws:

IOException

InspectableFileCachedInputStream

public InspectableFileCachedInputStream(int bufferSize)
                                 throws IOException

Creates a new instance with specified buffer size and default overflow-file directory.

Parameters:

bufferSize - the buffer size, in bytes.

Throws:

IOException

InspectableFileCachedInputStream

public InspectableFileCachedInputStream()
                                 throws IOException

Creates a new instance with default buffer size and overflow-file directory.

Throws:

IOException

Method Detail

clear

public void clear()
           throws IOException

Clears the content of this InspectableFileCachedInputStream, zeroing the length of the represented stream.

Throws:

IOException

write

public int write(ByteBuffer byteBuffer)
          throws IOException

Appends the content of a specified buffer to the end of the currently represented stream.

Specified by:

write in interface WritableByteChannel

Parameters:

byteBuffer - a byte buffer.

Returns:

the number of bytes appended (i.e., byteBuffer.remaining()).

Throws:

IOException

truncate

public void truncate(long size)
              throws FileNotFoundException,
                     IOException

Truncates the overflow file to a given size if possible.

Parameters:

size - the new size; the final size is the maximum between the current write position (i.e., the length of the represented stream minus the length of the inspection buffer) and this value.

Throws:

FileNotFoundException

IOException

close

public void close()

Makes the stream unreadable until the next clear().

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Channel

Specified by:

close in interface Closeable

Overrides:

close in class InputStream

See Also:

reopen()

reopen

public void reopen()
            throws IOException

Makes the stream readable again after a close().

Throws:

IOException

See Also:

close()

dispose

public void dispose()
             throws IOException

Disposes this stream, deleting the overflow file. After that, the stream is unusable.

Throws:

IOException

available

public int available()
              throws IOException

Overrides:

available in class InputStream

Throws:

IOException

read

public int read(byte[] b,
                int offset,
                int length)
         throws IOException

Overrides:

read in class InputStream

Throws:

IOException

read

public int read(byte[] b)
         throws IOException

Overrides:

read in class InputStream

Throws:

IOException

skip

public long skip(long n)
          throws IOException

Overrides:

skip in class InputStream

Throws:

IOException

read

public int read()
         throws IOException

Specified by:

read in class InputStream

Throws:

IOException

length

public long length()
            throws IOException

Description copied from interface: MeasurableStream

Returns the overall length of this stream (optional operation). In most cases, this will require the stream to perform some extra action, possibly changing the state of the input stream itself (typically, reading all the bytes up to the end, or flushing on output stream). Implementing classes should always document what state will the input stream be in after calling this method, and which kind of exception could be thrown.

Specified by:

length in interface MeasurableStream

Throws:

IOException

position

public long position()
              throws IOException

Description copied from interface: RepositionableStream

Returns the current stream position.

Specified by:

position in interface MeasurableStream

Specified by:

position in interface RepositionableStream

Returns:

the current stream position.

Throws:

IOException

position

public void position(long position)
              throws IOException

Positions the input stream.

Specified by:

position in interface RepositionableStream

Parameters:

position - the new position (will be minimized with length()).

Throws:

IOException

isOpen

public boolean isOpen()

Specified by:

isOpen in interface Channel

mark

public void mark(int readlimit)

Overrides:

mark in class InputStream

reset

public void reset()
           throws IOException

Overrides:

reset in class InputStream

Throws:

IOException

markSupported

public boolean markSupported()

Overrides:

markSupported in class InputStream