src/hdfs/org/apache/hadoop/hdfs/protocol/LocatedBlocks.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.hdfs.protocol;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.List;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;

import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableFactories;
import org.apache.hadoop.io.WritableFactory;

/**
 * Collection of blocks with their locations and the file length.
 */
public class LocatedBlocks implements Writable {
  private long fileLength;
  private List<LocatedBlock> blocks; // array of blocks with prioritized locations
  private boolean underConstruction;

  LocatedBlocks() {
    fileLength = 0;
    blocks = null;
    underConstruction = false;
  }
  
  public LocatedBlocks(long flength, List<LocatedBlock> blks, boolean isUnderConstuction) {

    fileLength = flength;
    blocks = blks;
    underConstruction = isUnderConstuction;
  }
  
  /**
   * Get located blocks.
   */
  public List<LocatedBlock> getLocatedBlocks() {
    return blocks;
  }
  
  /**
   * Get located block.
   */
  public LocatedBlock get(int index) {
    return blocks.get(index);
  }
  
  /**
   * Get number of located blocks.
   */
  public int locatedBlockCount() {
    return blocks == null ? 0 : blocks.size();
  }

  /**
   * 
   */
  public long getFileLength() {
    return this.fileLength;
  }

  /**
   * Return ture if file was under construction when 
   * this LocatedBlocks was constructed, false otherwise.
   */
  public boolean isUnderConstruction() {
    return underConstruction;
  }
  
  /**
   * Find block containing specified offset.
   * 
   * @return block if found, or null otherwise.
   */
  public int findBlock(long offset) {
    // create fake block of size 1 as a key
    LocatedBlock key = new LocatedBlock();
    key.setStartOffset(offset);
    key.getBlock().setNumBytes(1);
    Comparator<LocatedBlock> comp = 
      new Comparator<LocatedBlock>() {
        // Returns 0 iff a is inside b or b is inside a
        public int compare(LocatedBlock a, LocatedBlock b) {
          long aBeg = a.getStartOffset();
          long bBeg = b.getStartOffset();
          long aEnd = aBeg + a.getBlockSize();
          long bEnd = bBeg + b.getBlockSize();
          if(aBeg <= bBeg && bEnd <= aEnd 
              || bBeg <= aBeg && aEnd <= bEnd)
            return 0; // one of the blocks is inside the other
          if(aBeg < bBeg)
            return -1; // a's left bound is to the left of the b's
          return 1;
        }
      };
    return Collections.binarySearch(blocks, key, comp);
  }
  
  public void insertRange(int blockIdx, List<LocatedBlock> newBlocks) {
    int oldIdx = blockIdx;
    int insStart = 0, insEnd = 0;
    for(int newIdx = 0; newIdx < newBlocks.size() && oldIdx < blocks.size(); 
                                                        newIdx++) {
      long newOff = newBlocks.get(newIdx).getStartOffset();
      long oldOff = blocks.get(oldIdx).getStartOffset();
      if(newOff < oldOff) {
        insEnd++;
      } else if(newOff == oldOff) {
        // replace old cached block by the new one
        blocks.set(oldIdx, newBlocks.get(newIdx));
        if(insStart < insEnd) { // insert new blocks
          blocks.addAll(oldIdx, newBlocks.subList(insStart, insEnd));
          oldIdx += insEnd - insStart;
        }
        insStart = insEnd = newIdx+1;
        oldIdx++;
      } else {  // newOff > oldOff
        assert false : "List of LocatedBlock must be sorted by startOffset";
      }
    }
    insEnd = newBlocks.size();
    if(insStart < insEnd) { // insert new blocks
      blocks.addAll(oldIdx, newBlocks.subList(insStart, insEnd));
    }
  }
  
  public static int getInsertIndex(int binSearchResult) {
    return binSearchResult >= 0 ? binSearchResult : -(binSearchResult+1);
  }

  //////////////////////////////////////////////////
  // Writable
  //////////////////////////////////////////////////
  static {                                      // register a ctor
    WritableFactories.setFactory
      (LocatedBlocks.class,
       new WritableFactory() {
         public Writable newInstance() { return new LocatedBlocks(); }
       });
  }

  public void write(DataOutput out) throws IOException {
    out.writeLong(this.fileLength);
    out.writeBoolean(underConstruction);
    // write located blocks
    int nrBlocks = locatedBlockCount();
    out.writeInt(nrBlocks);
    if (nrBlocks == 0) {
      return;
    }
    for (LocatedBlock blk : this.blocks) {
      blk.write(out);
    }
  }
  
  public void readFields(DataInput in) throws IOException {
    this.fileLength = in.readLong();
    underConstruction = in.readBoolean();
    // read located blocks
    int nrBlocks = in.readInt();
    this.blocks = new ArrayList<LocatedBlock>(nrBlocks);
    for (int idx = 0; idx < nrBlocks; idx++) {
      LocatedBlock blk = new LocatedBlock();
      blk.readFields(in);
      this.blocks.add(blk);
    }
  }
}