it.unimi.dsi.io

Class ByteBufferInputStream

java.lang.Object

java.io.InputStream

it.unimi.dsi.fastutil.io.MeasurableInputStream

it.unimi.dsi.io.ByteBufferInputStream

All Implemented Interfaces:

MeasurableStream, RepositionableStream, Closeable, AutoCloseable

public class ByteBufferInputStream
extends MeasurableInputStream
implements RepositionableStream

A bridge between byte buffers and input streams.

Java's memory-mapping facilities have the severe limitation of mapping at most Integer.MAX_VALUE bytes, as they expose the content of a file using a MappedByteBuffer. This class can expose a file of arbitrary length as a repositionable MeasurableInputStream that is actually based on an array of MappedByteBuffers, each mapping a chunk of CHUNK_SIZE bytes.

Since:

1.2

Author:

Sebastiano Vigna

Field Summary

Fields

Modifier and Type	Field and Description
static long	CHUNK_SIZE The size of a chunk created by map(FileChannel, FileChannel.MapMode).

Constructor Summary

Constructors

Modifier	Constructor and Description
	ByteBufferInputStream(ByteBuffer byteBuffer) Creates a new byte-buffer input stream from a single ByteBuffer.
protected	ByteBufferInputStream(ByteBuffer[] byteBuffer, long size, int curr, boolean[] readyToUse) Creates a new byte-buffer input stream.

Method Summary

Methods

Modifier and Type	Method and Description
int	available()
ByteBufferInputStream	copy()
long	length()
static ByteBufferInputStream	map(FileChannel fileChannel) Creates a new read-only byte-buffer input stream by mapping a given file channel.
static ByteBufferInputStream	map(FileChannel fileChannel, FileChannel.MapMode mapMode) Creates a new byte-buffer input stream by mapping a given file channel.
void	mark(int unused)
boolean	markSupported()
long	position()
void	position(long newPosition)
int	read()
int	read(byte[] b, int offset, int length)
void	reset()
long	skip(long n)

Methods inherited from class java.io.InputStream

close, read

Methods inherited from class java.lang.Object

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

Field Detail

CHUNK_SIZE

public static final long CHUNK_SIZE

The size of a chunk created by map(FileChannel, FileChannel.MapMode).

Constructor Detail

ByteBufferInputStream

public ByteBufferInputStream(ByteBuffer byteBuffer)

Creates a new byte-buffer input stream from a single ByteBuffer.

Parameters:

byteBuffer - the underlying byte buffer.

ByteBufferInputStream

protected ByteBufferInputStream(ByteBuffer[] byteBuffer,
                     long size,
                     int curr,
                     boolean[] readyToUse)

Creates a new byte-buffer input stream.

Parameters:

byteBuffer - the underlying byte buffers.

size - the sum of the capacities of the byte buffers.

curr - the current buffer (reading will start at this buffer from its current position).

readyToUse - an array parallel to byteBuffer specifying which buffers do not need to be duplicated before being used (the process will happen lazily); the array will be used internally by the newly created byte-buffer input stream.

Method Detail

map

public static ByteBufferInputStream map(FileChannel fileChannel)
                                 throws IOException

Creates a new read-only byte-buffer input stream by mapping a given file channel.

Parameters:

fileChannel - the file channel that will be mapped.

Returns:

a new read-only byte-buffer input stream over the contents of fileChannel.

Throws:

IOException

map

public static ByteBufferInputStream map(FileChannel fileChannel,
                        FileChannel.MapMode mapMode)
                                 throws IOException

Creates a new byte-buffer input stream by mapping a given file channel.

Parameters:

fileChannel - the file channel that will be mapped.

mapMode - this must be FileChannel.MapMode.READ_ONLY.

Returns:

a new byte-buffer input stream over the contents of fileChannel.

Throws:

IOException

available

public int available()

Overrides:

available in class InputStream

markSupported

public boolean markSupported()

Overrides:

markSupported in class InputStream

mark

public void mark(int unused)

Overrides:

mark in class InputStream

reset

public void reset()
           throws IOException

Overrides:

reset in class InputStream

Throws:

IOException

skip

public long skip(long n)
          throws IOException

Overrides:

skip in class InputStream

Throws:

IOException

read

public int read()

Specified by:

read in class InputStream

read

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

Overrides:

read in class InputStream

length

public long length()

Specified by:

length in interface MeasurableStream

position

public long position()

Specified by:

position in interface MeasurableStream

Specified by:

position in interface RepositionableStream

position

public void position(long newPosition)

Specified by:

position in interface RepositionableStream

copy

public ByteBufferInputStream copy()