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The Apache Commons IO library contains utility classes, stream implementations, file filters,
file comparators, endian transformation classes, and much more.
/*
* 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.lang.reflect.Field;
import java.lang.reflect.Method;
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;
/**
* {@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.
*
* This class was ported and adapted from Apache Spark commit 933dc6cb7b3de1d8ccaf73d124d6eb95b947ed19 where it was
* called {@code NioBufferedFileInputStream}.
*
*
* @since 2.9.0
*/
@SuppressWarnings("restriction")
public final class BufferedFileChannelInputStream extends InputStream {
private final ByteBuffer byteBuffer;
private final FileChannel fileChannel;
private static final Class DIRECT_BUFFER_CLASS = getDirectBufferClass();
private static Class getDirectBufferClass() {
Class res = null;
try {
res = Class.forName("sun.nio.ch.DirectBuffer");
} catch (IllegalAccessError | ClassNotFoundException ignored) {
// ignored
}
return res;
}
private static boolean isDirectBuffer(final Object object) {
return DIRECT_BUFFER_CLASS != null && DIRECT_BUFFER_CLASS.isInstance(object);
}
/**
* Constructs a new instance for the given File.
*
* @param file The file to stream.
* @throws IOException If an I/O error occurs
*/
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 bufferSizeInBytes buffer size.
* @throws IOException If an I/O error occurs
*/
public BufferedFileChannelInputStream(final File file, final int bufferSizeInBytes) throws IOException {
this(file.toPath(), bufferSizeInBytes);
}
/**
* Constructs a new instance for the given Path.
*
* @param path The path to stream.
* @throws IOException If an I/O error occurs
*/
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 bufferSizeInBytes buffer size.
* @throws IOException If an I/O error occurs
*/
public BufferedFileChannelInputStream(final Path path, final int bufferSizeInBytes) throws IOException {
Objects.requireNonNull(path, "path");
fileChannel = FileChannel.open(path, StandardOpenOption.READ);
byteBuffer = ByteBuffer.allocateDirect(bufferSizeInBytes);
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 (isDirectBuffer(buffer)) {
cleanDirectBuffer(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.
*
* @param buffer the buffer to clean. must be a DirectBuffer.
*/
private void cleanDirectBuffer(final ByteBuffer buffer) {
//
// Ported from StorageUtils.scala.
//
// private val bufferCleaner: DirectBuffer => Unit =
// if (SystemUtils.isJavaVersionAtLeast(JavaVersion.JAVA_9)) {
// val cleanerMethod =
// Utils.classForName("sun.misc.Unsafe").getMethod("invokeCleaner", classOf[ByteBuffer])
// val unsafeField = classOf[Unsafe].getDeclaredField("theUnsafe")
// unsafeField.setAccessible(true)
// val unsafe = unsafeField.get(null).asInstanceOf[Unsafe]
// buffer: DirectBuffer => cleanerMethod.invoke(unsafe, buffer)
// } else {
// val cleanerMethod = Utils.classForName("sun.misc.Cleaner").getMethod("clean")
// buffer: DirectBuffer => {
// // Careful to avoid the return type of .cleaner(), which changes with JDK
// val cleaner: AnyRef = buffer.cleaner()
// if (cleaner != null) {
// cleanerMethod.invoke(cleaner)
// }
// }
// }
//
final String specVer = System.getProperty("java.specification.version");
if ("1.8".equals(specVer)) {
// On Java 8, but also compiles on Java 11.
try {
final Class clsCleaner = Class.forName("sun.misc.Cleaner");
final Method cleanerMethod = DIRECT_BUFFER_CLASS.getMethod("cleaner");
final Object cleaner = cleanerMethod.invoke(buffer);
if (cleaner != null) {
final Method cleanMethod = clsCleaner.getMethod("clean");
cleanMethod.invoke(cleaner);
}
} catch (final ReflectiveOperationException e) {
throw new IllegalStateException(e);
}
} else {
// On Java 9 and up, but compiles on Java 8.
try {
final Class clsUnsafe = Class.forName("sun.misc.Unsafe");
final Method cleanerMethod = clsUnsafe.getMethod("invokeCleaner", ByteBuffer.class);
final Field unsafeField = clsUnsafe.getDeclaredField("theUnsafe");
unsafeField.setAccessible(true);
cleanerMethod.invoke(unsafeField.get(null), buffer);
} catch (final ReflectiveOperationException e) {
throw new IllegalStateException(e);
}
}
}
@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
*/
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;
}
}