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     */
018    package org.apache.hadoop.fs;
019    
020    import java.io.*;
021    import java.io.DataOutputStream;
022    import java.io.FilterOutputStream;
023    import java.io.IOException;
024    import java.io.OutputStream;
025    
026    import org.apache.hadoop.classification.InterfaceAudience;
027    import org.apache.hadoop.classification.InterfaceStability;
028    
029    /** Utility that wraps a {@link OutputStream} in a {@link DataOutputStream}.
030     */
031    @InterfaceAudience.Public
032    @InterfaceStability.Stable
033    public 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    }