content: /*
   * 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 com.google.common.base.Preconditions;
  
  import java.io.Closeable;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  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.
   *
   * @param <T1> the concrete input stream subclass
   * @param <T2> the concrete output stream subclass
   */
  @NotThreadSafe
  public final class OpenFileEntry<T1 extends InputStream, T2 extends OutputStream>
      implements Closeable {
    private final long mId;
    private final T1 mIn;
    private final T2 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, T1 in, T2 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 T1 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 T2 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.
     *
     * @param offset the new 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;
    }
  }
  