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Lucene example source code file (SegmentTermEnum.java)

This example Lucene source code file (SegmentTermEnum.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

corruptindexexception, fieldinfos, indexinput, io, ioexception, ioexception, override, override, segmenttermenum, term, termbuffer, termbuffer, termenum, terminfo, terminfo

The Lucene SegmentTermEnum.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 org.apache.lucene.store.IndexInput;

final class SegmentTermEnum extends TermEnum implements Cloneable {
  private IndexInput input;
  FieldInfos fieldInfos;
  long size;
  long position = -1;

  private TermBuffer termBuffer = new TermBuffer();
  private TermBuffer prevBuffer = new TermBuffer();
  private TermBuffer scanBuffer = new TermBuffer(); // used for scanning

  private TermInfo termInfo = new TermInfo();

  private int format;
  private boolean isIndex = false;
  long indexPointer = 0;
  int indexInterval;
  int skipInterval;
  int maxSkipLevels;
  private int formatM1SkipInterval;

  SegmentTermEnum(IndexInput i, FieldInfos fis, boolean isi)
          throws CorruptIndexException, IOException {
    input = i;
    fieldInfos = fis;
    isIndex = isi;
    maxSkipLevels = 1; // use single-level skip lists for formats > -3 
    
    int firstInt = input.readInt();
    if (firstInt >= 0) {
      // original-format file, without explicit format version number
      format = 0;
      size = firstInt;

      // back-compatible settings
      indexInterval = 128;
      skipInterval = Integer.MAX_VALUE; // switch off skipTo optimization
    } else {
      // we have a format version number
      format = firstInt;

      // check that it is a format we can understand
      if (format < TermInfosWriter.FORMAT_CURRENT)
        throw new CorruptIndexException("Unknown format version:" + format + " expected " + TermInfosWriter.FORMAT_CURRENT + " or higher");

      size = input.readLong();                    // read the size
      
      if(format == -1){
        if (!isIndex) {
          indexInterval = input.readInt();
          formatM1SkipInterval = input.readInt();
        }
        // switch off skipTo optimization for file format prior to 1.4rc2 in order to avoid a bug in 
        // skipTo implementation of these versions
        skipInterval = Integer.MAX_VALUE;
      } else {
        indexInterval = input.readInt();
        skipInterval = input.readInt();
        if (format <= TermInfosWriter.FORMAT) {
          // this new format introduces multi-level skipping
          maxSkipLevels = input.readInt();
        }
      }
      assert indexInterval > 0: "indexInterval=" + indexInterval + " is negative; must be > 0";
      assert skipInterval > 0: "skipInterval=" + skipInterval + " is negative; must be > 0";
    }
    if (format > TermInfosWriter.FORMAT_VERSION_UTF8_LENGTH_IN_BYTES) {
      termBuffer.setPreUTF8Strings();
      scanBuffer.setPreUTF8Strings();
      prevBuffer.setPreUTF8Strings();
    }
  }

  @Override
  protected Object clone() {
    SegmentTermEnum clone = null;
    try {
      clone = (SegmentTermEnum) super.clone();
    } catch (CloneNotSupportedException e) {}

    clone.input = (IndexInput) input.clone();
    clone.termInfo = new TermInfo(termInfo);

    clone.termBuffer = (TermBuffer)termBuffer.clone();
    clone.prevBuffer = (TermBuffer)prevBuffer.clone();
    clone.scanBuffer = new TermBuffer();

    return clone;
  }

  final void seek(long pointer, long p, Term t, TermInfo ti)
          throws IOException {
    input.seek(pointer);
    position = p;
    termBuffer.set(t);
    prevBuffer.reset();
    termInfo.set(ti);
  }

  /** Increments the enumeration to the next element.  True if one exists.*/
  @Override
  public final boolean next() throws IOException {
    if (position++ >= size - 1) {
      prevBuffer.set(termBuffer);
      termBuffer.reset();
      return false;
    }

    prevBuffer.set(termBuffer);
    termBuffer.read(input, fieldInfos);

    termInfo.docFreq = input.readVInt();	  // read doc freq
    termInfo.freqPointer += input.readVLong();	  // read freq pointer
    termInfo.proxPointer += input.readVLong();	  // read prox pointer
    
    if(format == -1){
    //  just read skipOffset in order to increment  file pointer; 
    // value is never used since skipTo is switched off
      if (!isIndex) {
        if (termInfo.docFreq > formatM1SkipInterval) {
          termInfo.skipOffset = input.readVInt(); 
        }
      }
    }
    else{
      if (termInfo.docFreq >= skipInterval) 
        termInfo.skipOffset = input.readVInt();
    }
    
    if (isIndex)
      indexPointer += input.readVLong();	  // read index pointer

    return true;
  }

  /* Optimized scan, without allocating new terms. 
   *  Return number of invocations to next().
   *
   * NOTE: LUCENE-3183: if you pass Term("", "") here then this
   * will incorrectly return before positioning the enum,
   * and position will be -1; caller must detect this. */
  final int scanTo(Term term) throws IOException {
    scanBuffer.set(term);
    int count = 0;
    while (scanBuffer.compareTo(termBuffer) > 0 && next()) {
      count++;
    }
    return count;
  }

  /** Returns the current Term in the enumeration.
   Initially invalid, valid after next() called for the first time.*/
  @Override
  public final Term term() {
    return termBuffer.toTerm();
  }

  /** Returns the previous Term enumerated. Initially null.*/
  final Term prev() {
    return prevBuffer.toTerm();
  }

  /** Returns the current TermInfo in the enumeration.
   Initially invalid, valid after next() called for the first time.*/
  final TermInfo termInfo() {
    return new TermInfo(termInfo);
  }

  /** Sets the argument to the current TermInfo in the enumeration.
   Initially invalid, valid after next() called for the first time.*/
  final void termInfo(TermInfo ti) {
    ti.set(termInfo);
  }

  /** Returns the docFreq from the current TermInfo in the enumeration.
   Initially invalid, valid after next() called for the first time.*/
  @Override
  public final int docFreq() {
    return termInfo.docFreq;
  }

  /* Returns the freqPointer from the current TermInfo in the enumeration.
    Initially invalid, valid after next() called for the first time.*/
  final long freqPointer() {
    return termInfo.freqPointer;
  }

  /* Returns the proxPointer from the current TermInfo in the enumeration.
    Initially invalid, valid after next() called for the first time.*/
  final long proxPointer() {
    return termInfo.proxPointer;
  }

  /** Closes the enumeration to further activity, freeing resources. */
  @Override
  public final void close() throws IOException {
    input.close();
  }
}

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