/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.lucene.store;
import java.io.EOFException;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.SeekableByteChannel;
import java.nio.channels.ClosedChannelException; // javadoc @link
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.util.concurrent.Future;
/** A straightforward implementation of {@link FSDirectory}
* using {@link Files#newByteChannel(Path, java.nio.file.OpenOption...)}.
* However, this class has
* poor concurrent performance (multiple threads will
* bottleneck) as it synchronizes when multiple threads
* read from the same file. It's usually better to use
* {@link NIOFSDirectory} or {@link MMapDirectory} instead.
* <p>
* <b>NOTE:</b> Accessing this class either directly or
* indirectly from a thread while it's interrupted can close the
* underlying file descriptor immediately if at the same time the thread is
* blocked on IO. The file descriptor will remain closed and subsequent access
* to {@link SimpleFSDirectory} will throw a {@link ClosedChannelException}. If
* your application uses either {@link Thread#interrupt()} or
* {@link Future#cancel(boolean)} you should use the legacy {@code RAFDirectory}
* from the Lucene {@code misc} module in favor of {@link SimpleFSDirectory}.
* </p>
*/
public class SimpleFSDirectory extends FSDirectory {
/** Create a new SimpleFSDirectory for the named location.
* The directory is created at the named location if it does not yet exist.
*
* @param path the path of the directory
* @param lockFactory the lock factory to use
* @throws IOException if there is a low-level I/O error
*/
public SimpleFSDirectory(Path path, LockFactory lockFactory) throws IOException {
super(path, lockFactory);
}
/** Create a new SimpleFSDirectory for the named location and {@link FSLockFactory#getDefault()}.
* The directory is created at the named location if it does not yet exist.
*
* @param path the path of the directory
* @throws IOException if there is a low-level I/O error
*/
public SimpleFSDirectory(Path path) throws IOException {
this(path, FSLockFactory.getDefault());
}
/** Creates an IndexInput for the file with the given name. */
@Override
public IndexInput openInput(String name, IOContext context) throws IOException {
ensureOpen();
ensureCanRead(name);
Path path = directory.resolve(name);
SeekableByteChannel channel = Files.newByteChannel(path, StandardOpenOption.READ);
return new SimpleFSIndexInput("SimpleFSIndexInput(path=\"" + path + "\")", channel, context);
}
/**
* Reads bytes with {@link SeekableByteChannel#read(ByteBuffer)}
*/
static final class SimpleFSIndexInput extends BufferedIndexInput {
/**
* The maximum chunk size for reads of 16384 bytes.
*/
private static final int CHUNK_SIZE = 16384;
/** the channel we will read from */
protected final SeekableByteChannel channel;
/** is this instance a clone and hence does not own the file to close it */
boolean isClone = false;
/** start offset: non-zero in the slice case */
protected final long off;
/** end offset (start+length) */
protected final long end;
private ByteBuffer byteBuf; // wraps the buffer for NIO
public SimpleFSIndexInput(String resourceDesc, SeekableByteChannel channel, IOContext context) throws IOException {
super(resourceDesc, context);
this.channel = channel;
this.off = 0L;
this.end = channel.size();
}
public SimpleFSIndexInput(String resourceDesc, SeekableByteChannel channel, long off, long length, int bufferSize) {
super(resourceDesc, bufferSize);
this.channel = channel;
this.off = off;
this.end = off + length;
this.isClone = true;
}
@Override
public void close() throws IOException {
if (!isClone) {
channel.close();
}
}
@Override
public SimpleFSIndexInput clone() {
SimpleFSIndexInput clone = (SimpleFSIndexInput)super.clone();
clone.isClone = true;
return clone;
}
@Override
public IndexInput slice(String sliceDescription, long offset, long length) throws IOException {
if (offset < 0 || length < 0 || offset + length > this.length()) {
throw new IllegalArgumentException("slice() " + sliceDescription + " out of bounds: offset=" + offset + ",length=" + length + ",fileLength=" + this.length() + ": " + this);
}
return new SimpleFSIndexInput(getFullSliceDescription(sliceDescription), channel, off + offset, length, getBufferSize());
}
@Override
public final long length() {
return end - off;
}
@Override
protected void newBuffer(byte[] newBuffer) {
super.newBuffer(newBuffer);
byteBuf = ByteBuffer.wrap(newBuffer);
}
@Override
protected void readInternal(byte[] b, int offset, int len) throws IOException {
final ByteBuffer bb;
// Determine the ByteBuffer we should use
if (b == buffer) {
// Use our own pre-wrapped byteBuf:
assert byteBuf != null;
bb = byteBuf;
byteBuf.clear().position(offset);
} else {
bb = ByteBuffer.wrap(b, offset, len);
}
synchronized(channel) {
long pos = getFilePointer() + off;
if (pos + len > end) {
throw new EOFException("read past EOF: " + this);
}
try {
channel.position(pos);
int readLength = len;
while (readLength > 0) {
final int toRead = Math.min(CHUNK_SIZE, readLength);
bb.limit(bb.position() + toRead);
assert bb.remaining() == toRead;
final int i = channel.read(bb);
if (i < 0) { // be defensive here, even though we checked before hand, something could have changed
throw new EOFException("read past EOF: " + this + " off: " + offset + " len: " + len + " pos: " + pos + " chunkLen: " + toRead + " end: " + end);
}
assert i > 0 : "SeekableByteChannel.read with non zero-length bb.remaining() must always read at least one byte (Channel is in blocking mode, see spec of ReadableByteChannel)";
pos += i;
readLength -= i;
}
assert readLength == 0;
} catch (IOException ioe) {
throw new IOException(ioe.getMessage() + ": " + this, ioe);
}
}
}
@Override
protected void seekInternal(long pos) throws IOException {
if (pos > length()) {
throw new EOFException("read past EOF: pos=" + pos + " vs length=" + length() + ": " + this);
}
}
}
}