org.apache.commons.io.input

Class BufferedFileChannelInputStream

java.lang.Object

java.io.InputStream

org.apache.commons.io.input.BufferedFileChannelInputStream

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

public final class BufferedFileChannelInputStream
extends java.io.InputStream

InputStream implementation which uses direct buffer to read a file to avoid extra copy of data between Java and native memory which happens when using BufferedInputStream. Unfortunately, this is not something already available in JDK, sun.nio.ch.ChannelInputStream supports reading a file using NIO, but does not support buffering.

This class was ported and adapted from Apache Spark commit 933dc6cb7b3de1d8ccaf73d124d6eb95b947ed19 where it was called NioBufferedFileInputStream.

Since:

2.9.0

Field Summary

Fields

Modifier and Type	Field and Description
private java.nio.ByteBuffer	byteBuffer
private static java.lang.Class<?>	DIRECT_BUFFER_CLASS
private java.nio.channels.FileChannel	fileChannel

Constructor Summary

Constructors

Constructor and Description
BufferedFileChannelInputStream(java.io.File file) Constructs a new instance for the given File.
BufferedFileChannelInputStream(java.io.File file, int bufferSizeInBytes) Constructs a new instance for the given File and buffer size.
BufferedFileChannelInputStream(java.nio.file.Path path) Constructs a new instance for the given Path.
BufferedFileChannelInputStream(java.nio.file.Path path, int bufferSizeInBytes) Constructs a new instance for the given Path and buffer size.

Method Summary

Modifier and Type	Method and Description
int	available()
private void	clean(java.nio.ByteBuffer buffer) Attempts to clean up a ByteBuffer if it is direct or memory-mapped.
private void	cleanDirectBuffer(java.nio.ByteBuffer buffer) In Java 8, the type of DirectBuffer.cleaner() was sun.misc.Cleaner, and it was possible to access the method sun.misc.Cleaner.clean() to invoke it.
void	close()
private static java.lang.Class<?>	getDirectBufferClass()
private static boolean	isDirectBuffer(java.lang.Object object)
int	read()
int	read(byte[] b, int offset, int len)
private boolean	refill() Checks whether data is left to be read from the input stream.
long	skip(long n)
private long	skipFromFileChannel(long n)

Methods inherited from class java.io.InputStream

mark, markSupported, read, reset

Methods inherited from class java.lang.Object

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

Field Detail

byteBuffer

private final java.nio.ByteBuffer byteBuffer

fileChannel

private final java.nio.channels.FileChannel fileChannel

DIRECT_BUFFER_CLASS

private static final java.lang.Class<?> DIRECT_BUFFER_CLASS

Constructor Detail

BufferedFileChannelInputStream

public BufferedFileChannelInputStream(java.io.File file)
                               throws java.io.IOException

Constructs a new instance for the given File.

Parameters:

file - The file to stream.

Throws:

java.io.IOException - If an I/O error occurs

BufferedFileChannelInputStream

public BufferedFileChannelInputStream(java.io.File file,
                                      int bufferSizeInBytes)
                               throws java.io.IOException

Constructs a new instance for the given File and buffer size.

Parameters:

file - The file to stream.

bufferSizeInBytes - buffer size.

Throws:

java.io.IOException - If an I/O error occurs

BufferedFileChannelInputStream

public BufferedFileChannelInputStream(java.nio.file.Path path)
                               throws java.io.IOException

Constructs a new instance for the given Path.

Parameters:

path - The path to stream.

Throws:

java.io.IOException - If an I/O error occurs

BufferedFileChannelInputStream

public BufferedFileChannelInputStream(java.nio.file.Path path,
                                      int bufferSizeInBytes)
                               throws java.io.IOException

Constructs a new instance for the given Path and buffer size.

Parameters:

path - The path to stream.

bufferSizeInBytes - buffer size.

Throws:

java.io.IOException - If an I/O error occurs

Method Detail

getDirectBufferClass

private static java.lang.Class<?> getDirectBufferClass()

isDirectBuffer

private static boolean isDirectBuffer(java.lang.Object object)

available

public int available()
              throws java.io.IOException

Overrides:

available in class java.io.InputStream

Throws:

java.io.IOException

clean

private void clean(java.nio.ByteBuffer buffer)

Attempts to clean up a ByteBuffer if it is direct or memory-mapped. This uses an *unsafe* Sun API that will cause errors if one attempts to read from the disposed buffer. However, neither the bytes allocated to direct buffers nor file descriptors opened for memory-mapped buffers put pressure on the garbage collector. Waiting for garbage collection may lead to the depletion of off-heap memory or huge numbers of open files. There's unfortunately no standard API to manually dispose of these kinds of buffers.

Parameters:

buffer - the buffer to clean.

cleanDirectBuffer

private void cleanDirectBuffer(java.nio.ByteBuffer buffer)

In Java 8, the type of DirectBuffer.cleaner() was sun.misc.Cleaner, and it was possible to access the method sun.misc.Cleaner.clean() to invoke it. The type changed to jdk.internal.ref.Cleaner in later JDKs, and the .clean() method is not accessible even with reflection. However sun.misc.Unsafe added a invokeCleaner() method in JDK 9+ and this is still accessible with reflection.

Parameters:

buffer - the buffer to clean. must be a DirectBuffer.

close

public void close()
           throws java.io.IOException

Specified by:

close in interface java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable

Overrides:

close in class java.io.InputStream

Throws:

java.io.IOException

read

public int read()
         throws java.io.IOException

Specified by:

read in class java.io.InputStream

Throws:

java.io.IOException

read

public int read(byte[] b,
                int offset,
                int len)
         throws java.io.IOException

Overrides:

read in class java.io.InputStream

Throws:

java.io.IOException

refill

private boolean refill()
                throws java.io.IOException

Checks whether data is left to be read from the input stream.

Returns:

true if data is left, false otherwise

Throws:

java.io.IOException

skip

public long skip(long n)
          throws java.io.IOException

Overrides:

skip in class java.io.InputStream

Throws:

java.io.IOException

skipFromFileChannel

private long skipFromFileChannel(long n)
                          throws java.io.IOException

Throws:

java.io.IOException