hbase-common/src/main/java/org/apache/hadoop/hbase/codec/BaseDecoder.java

   1 /**
   2  * Licensed to the Apache Software Foundation (ASF) under one
   3  * or more contributor license agreements.  See the NOTICE file
   4  * distributed with this work for additional information
   5  * regarding copyright ownership.  The ASF licenses this file
   6  * to you under the Apache License, Version 2.0 (the
   7  * "License"); you may not use this file except in compliance
   8  * with the License.  You may obtain a copy of the License at
   9  *
  10  *     http://www.apache.org/licenses/LICENSE-2.0
  11  *
  12  * Unless required by applicable law or agreed to in writing, software
  13  * distributed under the License is distributed on an "AS IS" BASIS,
  14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  15  * See the License for the specific language governing permissions and
  16  * limitations under the License.
  17  */
  18 package org.apache.hadoop.hbase.codec;
  19
  20 import java.io.EOFException;
  21 import java.io.IOException;
  22 import java.io.InputStream;
  23 import java.io.PushbackInputStream;
  24
  25 import edu.umd.cs.findbugs.annotations.NonNull;
  26
  27 import org.apache.hadoop.hbase.Cell;
  28 import org.apache.hadoop.hbase.HBaseInterfaceAudience;
  29 import org.apache.yetus.audience.InterfaceAudience;
  30 import org.slf4j.Logger;
  31 import org.slf4j.LoggerFactory;
  32
  33 /**
  34  * TODO javadoc
  35  */
  36 @InterfaceAudience.LimitedPrivate({HBaseInterfaceAudience.COPROC, HBaseInterfaceAudience.PHOENIX})
  37 public abstract class BaseDecoder implements Codec.Decoder {
  38   protected static final Logger LOG = LoggerFactory.getLogger(BaseDecoder.class);
  39
  40   protected final InputStream in;
  41   private Cell current = null;
  42
  43   protected static class PBIS extends PushbackInputStream {
  44     public PBIS(InputStream in, int size) {
  45       super(in, size);
  46     }
  47
  48     public void resetBuf(int size) {
  49       this.buf = new byte[size];
  50       this.pos = size;
  51     }
  52   }
  53
  54   public BaseDecoder(final InputStream in) {
  55     this.in = new PBIS(in, 1);
  56   }
  57
  58   @Override
  59   public boolean advance() throws IOException {
  60     int firstByte = in.read();
  61     if (firstByte == -1) {
  62       return false;
  63     } else {
  64       ((PBIS)in).unread(firstByte);
  65     }
  66
  67     try {
  68       this.current = parseCell();
  69     } catch (IOException ioEx) {
  70       ((PBIS)in).resetBuf(1); // reset the buffer in case the underlying stream is read from upper layers
  71       rethrowEofException(ioEx);
  72     }
  73     return true;
  74   }
  75
  76   private void rethrowEofException(IOException ioEx) throws IOException {
  77     boolean isEof = false;
  78     try {
  79       isEof = this.in.available() == 0;
  80     } catch (Throwable t) {
  81       LOG.trace("Error getting available for error message - ignoring", t);
  82     }
  83     if (!isEof) throw ioEx;
  84     if (LOG.isTraceEnabled()) {
  85       LOG.trace("Partial cell read caused by EOF", ioEx);
  86     }
  87     EOFException eofEx = new EOFException("Partial cell read");
  88     eofEx.initCause(ioEx);
  89     throw eofEx;
  90   }
  91
  92   protected InputStream getInputStream() {
  93     return in;
  94   }
  95
  96   /**
  97    * Extract a Cell.
  98    * @return a parsed Cell or throws an Exception. EOFException or a generic IOException maybe
  99    * thrown if EOF is reached prematurely. Does not return null.
 100    * @throws IOException
 101    */
 102   @NonNull
 103   protected abstract Cell parseCell() throws IOException;
 104
 105   @Override
 106   public Cell current() {
 107     return this.current;
 108   }
 109 }