BufferedFileChannelInputStream.java
/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.io.input;
import static org.apache.commons.io.IOUtils.EOF;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.util.Objects;
import org.apache.commons.io.IOUtils;
import org.apache.commons.io.build.AbstractStreamBuilder;
/**
* {@link 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 {@link java.io.BufferedInputStream}. Unfortunately, this is not something already available in JDK, {@code sun.nio.ch.ChannelInputStream} supports
* reading a file using NIO, but does not support buffering.
* <p>
* To build an instance, use {@link Builder}.
* </p>
* <p>
* This class was ported and adapted from Apache Spark commit 933dc6cb7b3de1d8ccaf73d124d6eb95b947ed19 where it was called {@code NioBufferedFileInputStream}.
* </p>
*
* @see Builder
* @since 2.9.0
*/
public final class BufferedFileChannelInputStream extends InputStream {
// @formatter:off
/**
* Builds a new {@link BufferedFileChannelInputStream}.
*
* <p>
* Using File IO:
* </p>
* <pre>{@code
* BufferedFileChannelInputStream s = BufferedFileChannelInputStream.builder()
* .setFile(file)
* .setBufferSize(4096)
* .get();}
* </pre>
* <p>
* Using NIO Path:
* </p>
* <pre>{@code
* BufferedFileChannelInputStream s = BufferedFileChannelInputStream.builder()
* .setPath(path)
* .setBufferSize(4096)
* .get();}
* </pre>
*
* @see #get()
* @since 2.12.0
*/
// @formatter:on
public static class Builder extends AbstractStreamBuilder<BufferedFileChannelInputStream, Builder> {
/**
* Builds a new {@link BufferedFileChannelInputStream}.
* <p>
* You must set input that supports {@link #getInputStream()}, otherwise, this method throws an exception.
* </p>
* <p>
* This builder use the following aspects:
* </p>
* <ul>
* <li>{@link #getInputStream()}</li>
* <li>{@link #getBufferSize()}</li>
* </ul>
*
* @return a new instance.
* @throws IllegalStateException if the {@code origin} is {@code null}.
* @throws UnsupportedOperationException if the origin cannot be converted to a {@link Path}.
* @throws IOException If an I/O error occurs
* @see #getPath()
* @see #getBufferSize()
*/
@Override
public BufferedFileChannelInputStream get() throws IOException {
return new BufferedFileChannelInputStream(getPath(), getBufferSize());
}
}
/**
* Constructs a new {@link Builder}.
*
* @return a new {@link Builder}.
* @since 2.12.0
*/
public static Builder builder() {
return new Builder();
}
private final ByteBuffer byteBuffer;
private final FileChannel fileChannel;
/**
* Constructs a new instance for the given File.
*
* @param file The file to stream.
* @throws IOException If an I/O error occurs
* @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}
*/
@Deprecated
public BufferedFileChannelInputStream(final File file) throws IOException {
this(file, IOUtils.DEFAULT_BUFFER_SIZE);
}
/**
* Constructs a new instance for the given File and buffer size.
*
* @param file The file to stream.
* @param bufferSize buffer size.
* @throws IOException If an I/O error occurs
* @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}
*/
@Deprecated
public BufferedFileChannelInputStream(final File file, final int bufferSize) throws IOException {
this(file.toPath(), bufferSize);
}
/**
* Constructs a new instance for the given Path.
*
* @param path The path to stream.
* @throws IOException If an I/O error occurs
* @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}
*/
@Deprecated
public BufferedFileChannelInputStream(final Path path) throws IOException {
this(path, IOUtils.DEFAULT_BUFFER_SIZE);
}
/**
* Constructs a new instance for the given Path and buffer size.
*
* @param path The path to stream.
* @param bufferSize buffer size.
* @throws IOException If an I/O error occurs
* @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}
*/
@Deprecated
public BufferedFileChannelInputStream(final Path path, final int bufferSize) throws IOException {
Objects.requireNonNull(path, "path");
fileChannel = FileChannel.open(path, StandardOpenOption.READ);
byteBuffer = ByteBuffer.allocateDirect(bufferSize);
byteBuffer.flip();
}
@Override
public synchronized int available() throws IOException {
return byteBuffer.remaining();
}
/**
* 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.
*
* @param buffer the buffer to clean.
*/
private void clean(final ByteBuffer buffer) {
if (buffer.isDirect()) {
cleanDirectBuffer(buffer);
}
}
/**
* In Java 8, the type of {@code sun.nio.ch.DirectBuffer.cleaner()} was {@code sun.misc.Cleaner}, and it was possible to access the method
* {@code sun.misc.Cleaner.clean()} to invoke it. The type changed to {@code jdk.internal.ref.Cleaner} in later JDKs, and the {@code clean()} method is not
* accessible even with reflection. However {@code sun.misc.Unsafe} added an {@code invokeCleaner()} method in JDK 9+ and this is still accessible with
* reflection.
*
* @param buffer the buffer to clean. must be a DirectBuffer.
*/
private void cleanDirectBuffer(final ByteBuffer buffer) {
if (ByteBufferCleaner.isSupported()) {
ByteBufferCleaner.clean(buffer);
}
}
@Override
public synchronized void close() throws IOException {
try {
fileChannel.close();
} finally {
clean(byteBuffer);
}
}
@Override
public synchronized int read() throws IOException {
if (!refill()) {
return EOF;
}
return byteBuffer.get() & 0xFF;
}
@Override
public synchronized int read(final byte[] b, final int offset, int len) throws IOException {
if (offset < 0 || len < 0 || offset + len < 0 || offset + len > b.length) {
throw new IndexOutOfBoundsException();
}
if (!refill()) {
return EOF;
}
len = Math.min(len, byteBuffer.remaining());
byteBuffer.get(b, offset, len);
return len;
}
/**
* Checks whether data is left to be read from the input stream.
*
* @return true if data is left, false otherwise
* @throws IOException if an I/O error occurs.
*/
private boolean refill() throws IOException {
if (!byteBuffer.hasRemaining()) {
byteBuffer.clear();
int nRead = 0;
while (nRead == 0) {
nRead = fileChannel.read(byteBuffer);
}
byteBuffer.flip();
return nRead >= 0;
}
return true;
}
@Override
public synchronized long skip(final long n) throws IOException {
if (n <= 0L) {
return 0L;
}
if (byteBuffer.remaining() >= n) {
// The buffered content is enough to skip
byteBuffer.position(byteBuffer.position() + (int) n);
return n;
}
final long skippedFromBuffer = byteBuffer.remaining();
final long toSkipFromFileChannel = n - skippedFromBuffer;
// Discard everything we have read in the buffer.
byteBuffer.position(0);
byteBuffer.flip();
return skippedFromBuffer + skipFromFileChannel(toSkipFromFileChannel);
}
private long skipFromFileChannel(final long n) throws IOException {
final long currentFilePosition = fileChannel.position();
final long size = fileChannel.size();
if (n > size - currentFilePosition) {
fileChannel.position(size);
return size - currentFilePosition;
}
fileChannel.position(currentFilePosition + n);
return n;
}
}