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      out.close();
071    }
072  }
073
074  @Deprecated
075  public FSDataOutputStream(OutputStream out) throws IOException {
076    this(out, null);
077  }
078
079  public FSDataOutputStream(OutputStream out, FileSystem.Statistics stats)
080    throws IOException {
081    this(out, stats, 0);
082  }
083
084  public FSDataOutputStream(OutputStream out, FileSystem.Statistics stats,
085                            long startPosition) throws IOException {
086    super(new PositionCache(out, stats, startPosition));
087    wrappedStream = out;
088  }
089  
090  /**
091   * Get the current position in the output stream.
092   *
093   * @return the current position in the output stream
094   */
095  public long getPos() throws IOException {
096    return ((PositionCache)out).getPos();
097  }
098
099  /**
100   * Close the underlying output stream.
101   */
102  public void close() throws IOException {
103    out.close(); // This invokes PositionCache.close()
104  }
105
106  /**
107   * Get a reference to the wrapped output stream. Used by unit tests.
108   *
109   * @return the underlying output stream
110   */
111  @InterfaceAudience.LimitedPrivate({"HDFS"})
112  public OutputStream getWrappedStream() {
113    return wrappedStream;
114  }
115
116  @Override  // Syncable
117  @Deprecated
118  public void sync() throws IOException {
119    if (wrappedStream instanceof Syncable) {
120      ((Syncable)wrappedStream).sync();
121    }
122  }
123  
124  @Override  // Syncable
125  public void hflush() throws IOException {
126    if (wrappedStream instanceof Syncable) {
127      ((Syncable)wrappedStream).hflush();
128    } else {
129      wrappedStream.flush();
130    }
131  }
132  
133  @Override  // Syncable
134  public void hsync() throws IOException {
135    if (wrappedStream instanceof Syncable) {
136      ((Syncable)wrappedStream).hsync();
137    } else {
138      wrappedStream.flush();
139    }
140  }
141
142  @Override
143  public void setDropBehind(Boolean dropBehind) throws IOException {
144    try {
145      ((CanSetDropBehind)wrappedStream).setDropBehind(dropBehind);
146    } catch (ClassCastException e) {
147      throw new UnsupportedOperationException("the wrapped stream does " +
148          "not support setting the drop-behind caching setting.");
149    }
150  }
151
152  // mapr_extensibility
153  public long[] getFidServers() throws IOException {
154    throw new UnsupportedOperationException();
155  }
156}