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Mount Alluxio as a FUSE file system
/*
* The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
* (the "License"). You may not use this work except in compliance with the License, which is
* available at www.apache.org/licenses/LICENSE-2.0
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
* either express or implied, as more fully set forth in the License.
*
* See the NOTICE file distributed with this work for information regarding copyright ownership.
*/
package alluxio.fuse;
import alluxio.client.file.FileInStream;
import alluxio.client.file.FileOutStream;
import com.google.common.base.Preconditions;
import java.io.Closeable;
import java.io.IOException;
import javax.annotation.Nullable;
import javax.annotation.concurrent.NotThreadSafe;
/**
* Convenience class to encapsulate input/output streams of open alluxio files.
*
* An open file can be either write-only or read-only, never both. This means that one of getIn or
* getOut will be null, while the other will be non-null. It is up to the user of this class
* (currently, only {@link AlluxioFuseFileSystem}) to check that.
*
* This mechanism is preferred over more complex sub-classing to avoid useless casts or type checks
* for every read/write call, which happen quite often.
*/
@NotThreadSafe
final class OpenFileEntry implements Closeable {
private final long mId;
private final FileInStream mIn;
private final FileOutStream mOut;
// Path is likely to be changed when fuse rename() is called
private String mPath;
/** the next write offset. */
private long mOffset;
/**
* Constructs a new {@link OpenFileEntry} for an Alluxio file.
*
* @param id the id of the file
* @param path the path of the file
* @param in the input stream of the file
* @param out the output stream of the file
*/
public OpenFileEntry(long id, String path, FileInStream in, FileOutStream out) {
Preconditions.checkArgument(id != -1 && !path.isEmpty());
Preconditions.checkArgument(in != null || out != null);
mId = id;
mIn = in;
mOut = out;
mPath = path;
mOffset = -1;
}
/**
* @return the id of the file
*/
public long getId() {
return mId;
}
/**
* @return the path of the file
*/
public String getPath() {
return mPath;
}
/**
* Gets the opened input stream for this open file entry. The value returned can be {@code null}
* if the file is not open for reading.
*
* @return an opened input stream for the open alluxio file, or null
*/
@Nullable
public FileInStream getIn() {
return mIn;
}
/**
* Gets the opened output stream for this open file entry. The value returned can be {@code null}
* if the file is not open for writing.
*
* @return an opened input stream for the open alluxio file, or null
*/
@Nullable
public FileOutStream getOut() {
return mOut;
}
/**
* @return the offset of the next write
*/
public long getWriteOffset() {
return mOffset;
}
/**
* Sets the path of the file. The file path can be changed
* if fuse rename() is called.
*
* @param path the new path of the file
*/
public void setPath(String path) {
mPath = path;
}
/**
* Sets the offset of the next write.
*/
public void setWriteOffset(long offset) {
mOffset = offset;
}
/**
* Closes the underlying open streams.
*/
@Override
public void close() throws IOException {
if (mIn != null) {
mIn.close();
}
if (mOut != null) {
mOut.close();
}
mOffset = -1;
}
}
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