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Lucene example source code file (DefaultSkipListReader.java)

This example Lucene source code file (DefaultSkipListReader.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lucene tags/keywords

defaultskiplistreader, defaultskiplistreader, indexinput, indexinput, io, ioexception, ioexception, multilevelskiplistreader, override, override, util

The Lucene DefaultSkipListReader.java source code

package org.apache.lucene.index;

/**
 * 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.
 */

import java.io.IOException;
import java.util.Arrays;

import org.apache.lucene.store.IndexInput;

/**
 * Implements the skip list reader for the default posting list format
 * that stores positions and payloads.
 *
 */
class DefaultSkipListReader extends MultiLevelSkipListReader {
  private boolean currentFieldStoresPayloads;
  private long freqPointer[];
  private long proxPointer[];
  private int payloadLength[];
  
  private long lastFreqPointer;
  private long lastProxPointer;
  private int lastPayloadLength;
                           

  DefaultSkipListReader(IndexInput skipStream, int maxSkipLevels, int skipInterval) {
    super(skipStream, maxSkipLevels, skipInterval);
    freqPointer = new long[maxSkipLevels];
    proxPointer = new long[maxSkipLevels];
    payloadLength = new int[maxSkipLevels];
  }
  
  void init(long skipPointer, long freqBasePointer, long proxBasePointer, int df, boolean storesPayloads) {
    super.init(skipPointer, df);
    this.currentFieldStoresPayloads = storesPayloads;
    lastFreqPointer = freqBasePointer;
    lastProxPointer = proxBasePointer;

    Arrays.fill(freqPointer, freqBasePointer);
    Arrays.fill(proxPointer, proxBasePointer);
    Arrays.fill(payloadLength, 0);
  }

  /** Returns the freq pointer of the doc to which the last call of 
   * {@link MultiLevelSkipListReader#skipTo(int)} has skipped.  */
  long getFreqPointer() {
    return lastFreqPointer;
  }

  /** Returns the prox pointer of the doc to which the last call of 
   * {@link MultiLevelSkipListReader#skipTo(int)} has skipped.  */
  long getProxPointer() {
    return lastProxPointer;
  }
  
  /** Returns the payload length of the payload stored just before 
   * the doc to which the last call of {@link MultiLevelSkipListReader#skipTo(int)} 
   * has skipped.  */
  int getPayloadLength() {
    return lastPayloadLength;
  }
  
  @Override
  protected void seekChild(int level) throws IOException {
    super.seekChild(level);
    freqPointer[level] = lastFreqPointer;
    proxPointer[level] = lastProxPointer;
    payloadLength[level] = lastPayloadLength;
  }
  
  @Override
  protected void setLastSkipData(int level) {
    super.setLastSkipData(level);
    lastFreqPointer = freqPointer[level];
    lastProxPointer = proxPointer[level];
    lastPayloadLength = payloadLength[level];
  }


  @Override
  protected int readSkipData(int level, IndexInput skipStream) throws IOException {
    int delta;
    if (currentFieldStoresPayloads) {
      // the current field stores payloads.
      // if the doc delta is odd then we have
      // to read the current payload length
      // because it differs from the length of the
      // previous payload
      delta = skipStream.readVInt();
      if ((delta & 1) != 0) {
        payloadLength[level] = skipStream.readVInt();
      }
      delta >>>= 1;
    } else {
      delta = skipStream.readVInt();
    }
    freqPointer[level] += skipStream.readVInt();
    proxPointer[level] += skipStream.readVInt();
    
    return delta;
  }
}

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