001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.fs;
019
020import java.io.*;
021import java.io.DataOutputStream;
022import java.io.FilterOutputStream;
023import java.io.IOException;
024import java.io.OutputStream;
025
026import org.apache.hadoop.classification.InterfaceAudience;
027import org.apache.hadoop.classification.InterfaceStability;
028
029/** Utility that wraps a {@link OutputStream} in a {@link DataOutputStream}.
030 */
031@InterfaceAudience.Public
032@InterfaceStability.Stable
033public class FSDataOutputStream extends DataOutputStream
034    implements Syncable, CanSetDropBehind {
035  private final OutputStream wrappedStream;
036
037  private static class PositionCache extends FilterOutputStream {
038    private FileSystem.Statistics statistics;
039    long position;
040
041    public PositionCache(OutputStream out, 
042                         FileSystem.Statistics stats,
043                         long pos) throws IOException {
044      super(out);
045      statistics = stats;
046      position = pos;
047    }
048
049    public void write(int b) throws IOException {
050      out.write(b);
051      position++;
052      if (statistics != null) {
053        statistics.incrementBytesWritten(1);
054      }
055    }
056    
057    public void write(byte b[], int off, int len) throws IOException {
058      out.write(b, off, len);
059      position += len;                            // update position
060      if (statistics != null) {
061        statistics.incrementBytesWritten(len);
062      }
063    }
064      
065    public long getPos() throws IOException {
066      return position;                            // return cached position
067    }
068    
069    public void close() throws IOException {
070      // ensure close works even if a null reference was passed in
071      if (out != null) {
072        out.close();
073      }
074    }
075  }
076
077  @Deprecated
078  public FSDataOutputStream(OutputStream out) throws IOException {
079    this(out, null);
080  }
081
082  public FSDataOutputStream(OutputStream out, FileSystem.Statistics stats)
083    throws IOException {
084    this(out, stats, 0);
085  }
086
087  public FSDataOutputStream(OutputStream out, FileSystem.Statistics stats,
088                            long startPosition) throws IOException {
089    super(new PositionCache(out, stats, startPosition));
090    wrappedStream = out;
091  }
092  
093  /**
094   * Get the current position in the output stream.
095   *
096   * @return the current position in the output stream
097   */
098  public long getPos() throws IOException {
099    return ((PositionCache)out).getPos();
100  }
101
102  /**
103   * Close the underlying output stream.
104   */
105  public void close() throws IOException {
106    out.close(); // This invokes PositionCache.close()
107  }
108
109  /**
110   * Get a reference to the wrapped output stream.
111   *
112   * @return the underlying output stream
113   */
114  @InterfaceAudience.LimitedPrivate({"HDFS"})
115  public OutputStream getWrappedStream() {
116    return wrappedStream;
117  }
118
119  @Override  // Syncable
120  @Deprecated
121  public void sync() throws IOException {
122    if (wrappedStream instanceof Syncable) {
123      ((Syncable)wrappedStream).sync();
124    }
125  }
126  
127  @Override  // Syncable
128  public void hflush() throws IOException {
129    if (wrappedStream instanceof Syncable) {
130      ((Syncable)wrappedStream).hflush();
131    } else {
132      wrappedStream.flush();
133    }
134  }
135  
136  @Override  // Syncable
137  public void hsync() throws IOException {
138    if (wrappedStream instanceof Syncable) {
139      ((Syncable)wrappedStream).hsync();
140    } else {
141      wrappedStream.flush();
142    }
143  }
144
145  @Override
146  public void setDropBehind(Boolean dropBehind) throws IOException {
147    try {
148      ((CanSetDropBehind)wrappedStream).setDropBehind(dropBehind);
149    } catch (ClassCastException e) {
150      throw new UnsupportedOperationException("the wrapped stream does " +
151          "not support setting the drop-behind caching setting.");
152    }
153  }
154}