package org.apache.lucene.store;
/**
* 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.
*/
import java.io.File;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.ClosedChannelException; // javadoc @link
import java.nio.channels.FileChannel;
import java.util.concurrent.Future; // javadoc
/**
* An {@link FSDirectory} implementation that uses java.nio's FileChannel's
* positional read, which allows multiple threads to read from the same file
* without synchronizing.
* <p>
* This class only uses FileChannel when reading; writing is achieved with
* {@link SimpleFSDirectory.SimpleFSIndexOutput}.
* <p>
* <b>NOTE</b>: NIOFSDirectory is not recommended on Windows because of a bug in
* how FileChannel.read is implemented in Sun's JRE. Inside of the
* implementation the position is apparently synchronized. See <a
* href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6265734">here</a>
* for details.
* </p>
* <p>
* <font color="red"><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 NIOFSDirectory} will throw a {@link ClosedChannelException}. If
* your application uses either {@link Thread#interrupt()} or
* {@link Future#cancel(boolean)} you should use {@link SimpleFSDirectory} in
* favor of {@link NIOFSDirectory}.</font>
* </p>
*/
public class NIOFSDirectory extends FSDirectory {
/** Create a new NIOFSDirectory for the named location.
*
* @param path the path of the directory
* @param lockFactory the lock factory to use, or null for the default
* ({@link NativeFSLockFactory});
* @throws IOException
*/
public NIOFSDirectory(File path, LockFactory lockFactory) throws IOException {
super(path, lockFactory);
}
/** Create a new NIOFSDirectory for the named location and {@link NativeFSLockFactory}.
*
* @param path the path of the directory
* @throws IOException
*/
public NIOFSDirectory(File path) throws IOException {
super(path, null);
}
/** Creates an IndexInput for the file with the given name. */
@Override
public IndexInput openInput(String name, int bufferSize) throws IOException {
ensureOpen();
return new NIOFSIndexInput(new File(getFile(), name), bufferSize, getReadChunkSize());
}
/** Creates an IndexOutput for the file with the given name. */
@Override
public IndexOutput createOutput(String name) throws IOException {
initOutput(name);
return new SimpleFSDirectory.SimpleFSIndexOutput(new File(directory, name));
}
protected static class NIOFSIndexInput extends SimpleFSDirectory.SimpleFSIndexInput {
private ByteBuffer byteBuf; // wraps the buffer for NIO
private byte[] otherBuffer;
private ByteBuffer otherByteBuf;
final FileChannel channel;
public NIOFSIndexInput(File path, int bufferSize, int chunkSize) throws IOException {
super(path, bufferSize, chunkSize);
channel = file.getChannel();
}
@Override
protected void newBuffer(byte[] newBuffer) {
super.newBuffer(newBuffer);
byteBuf = ByteBuffer.wrap(newBuffer);
}
@Override
public void close() throws IOException {
if (!isClone && file.isOpen) {
// Close the channel & file
try {
channel.close();
} finally {
file.close();
}
}
}
@Override
protected void readInternal(byte[] b, int offset, int len) throws IOException {
final ByteBuffer bb;
// Determine the ByteBuffer we should use
if (b == buffer && 0 == offset) {
// Use our own pre-wrapped byteBuf:
assert byteBuf != null;
byteBuf.clear();
byteBuf.limit(len);
bb = byteBuf;
} else {
if (offset == 0) {
if (otherBuffer != b) {
// Now wrap this other buffer; with compound
// file, we are repeatedly called with its
// buffer, so we wrap it once and then re-use it
// on subsequent calls
otherBuffer = b;
otherByteBuf = ByteBuffer.wrap(b);
} else
otherByteBuf.clear();
otherByteBuf.limit(len);
bb = otherByteBuf;
} else {
// Always wrap when offset != 0
bb = ByteBuffer.wrap(b, offset, len);
}
}
int readOffset = bb.position();
int readLength = bb.limit() - readOffset;
assert readLength == len;
long pos = getFilePointer();
try {
while (readLength > 0) {
final int limit;
if (readLength > chunkSize) {
// LUCENE-1566 - work around JVM Bug by breaking
// very large reads into chunks
limit = readOffset + chunkSize;
} else {
limit = readOffset + readLength;
}
bb.limit(limit);
int i = channel.read(bb, pos);
if (i == -1) {
throw new IOException("read past EOF");
}
pos += i;
readOffset += i;
readLength -= i;
}
} catch (OutOfMemoryError e) {
// propagate OOM up and add a hint for 32bit VM Users hitting the bug
// with a large chunk size in the fast path.
final OutOfMemoryError outOfMemoryError = new OutOfMemoryError(
"OutOfMemoryError likely caused by the Sun VM Bug described in "
+ "https://issues.apache.org/jira/browse/LUCENE-1566; try calling FSDirectory.setReadChunkSize "
+ "with a a value smaller than the current chunk size (" + chunkSize + ")");
outOfMemoryError.initCause(e);
throw outOfMemoryError;
}
}
}
}