core/src/main/java/org/apache/hadoop/chukwa/datacollection/adaptor/filetailer/CharFileTailingAdaptorUTF8.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.chukwa.datacollection.adaptor.filetailer;


import org.apache.hadoop.chukwa.ChunkImpl;
import org.apache.hadoop.chukwa.datacollection.ChunkReceiver;
import java.util.ArrayList;

/**
 * A subclass of FileTailingAdaptor that reads UTF8/ascii files and splits
 * records at carriage returns.
 * 
 */
public class CharFileTailingAdaptorUTF8 extends FileTailingAdaptor {

  private static final char SEPARATOR = '\n';

  private ArrayList<Integer> offsets = new ArrayList<Integer>();

  /**
   * 
   * Note: this method uses a temporary ArrayList (shared across instances).
   * This means we're copying ints each time. This could be a performance issue.
   * Also, 'offsets' never shrinks, and will be of size proportional to the
   * largest number of lines ever seen in an event.
   */
  @Override
  protected int extractRecords(ChunkReceiver eq, long buffOffsetInFile,
      byte[] buf) throws InterruptedException {
    for (int i = 0; i < buf.length; ++i) {
      if (buf[i] == SEPARATOR) {
        offsets.add(i);
      }
    }

    if (offsets.size() > 0) {
      int[] offsets_i = new int[offsets.size()];
      for (int i = 0; i < offsets_i.length; ++i)
        offsets_i[i] = offsets.get(i);

      int bytesUsed = offsets_i[offsets_i.length - 1] + 1; // char at last
                                                           // offset uses a byte
      assert bytesUsed > 0 : " shouldn't send empty events";
      ChunkImpl event = new ChunkImpl(type, toWatch.getAbsolutePath(),
          buffOffsetInFile + bytesUsed, buf, this);

      event.setRecordOffsets(offsets_i);
      eq.add(event);

      offsets.clear();
      return bytesUsed;
    } else
      return 0;

  }

}