content: 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.ArrayList;
  import java.util.Comparator;
  import java.util.List;
  
  import org.apache.lucene.util.BitUtil;
  import org.apache.lucene.util.BytesRef;
  import org.apache.lucene.util.PagedBytes.PagedBytesDataInput;
  import org.apache.lucene.util.PagedBytes.PagedBytesDataOutput;
  import org.apache.lucene.util.PagedBytes;
  import org.apache.lucene.util.packed.GrowableWriter;
  import org.apache.lucene.util.packed.PackedInts;
  
  /**
   * This stores a monotonically increasing set of <Term, TermInfo> pairs in an
   * index segment. Pairs are accessed either by Term or by ordinal position the
   * set. The Terms and TermInfo are actually serialized and stored into a byte
   * array and pointers to the position of each are stored in a int array.
   */
  class TermInfosReaderIndex implements TermInfoReaderIndexInterface{
  
    private static final int MAX_PAGE_BITS = 18; // 256 KB block
    private Term[] fields;
    private int totalIndexInterval;
    private Comparator<BytesRef> comparator = BytesRef.getUTF8SortedAsUTF16Comparator();
    private final PagedBytesDataInput dataInput;
    private final PackedInts.Reader indexToDataOffset;
    private final int indexSize;
    private final int skipInterval;
  
    /**
     * Loads the segment information at segment load time.
     * 
     * @param indexEnum
     *          the term enum.
     * @param indexDivisor
     *          the index divisor.
     * @param tiiFileLength
     *          the size of the tii file, used to approximate the size of the
     *          buffer.
     * @param totalIndexInterval
     *          the total index interval.
     */
    TermInfosReaderIndex(SegmentTermEnum indexEnum, int indexDivisor, long tiiFileLength, int totalIndexInterval) throws IOException {
      this.totalIndexInterval = totalIndexInterval;
      indexSize = 1 + ((int) indexEnum.size - 1) / indexDivisor;
      skipInterval = indexEnum.skipInterval;
      // this is only an inital size, it will be GCed once the build is complete
      long initialSize = (long) (tiiFileLength * 1.5) / indexDivisor;
      PagedBytes dataPagedBytes = new PagedBytes(estimatePageBits(initialSize));
      PagedBytesDataOutput dataOutput = dataPagedBytes.getDataOutput();
  
      GrowableWriter indexToTerms = new GrowableWriter(4, indexSize, false);
      String currentField = null;
      List<String> fieldStrs = new ArrayList<String>();
      int fieldCounter = -1;
      for (int i = 0; indexEnum.next(); i++) {
        Term term = indexEnum.term();
        if (currentField != term.field) {
          currentField = term.field;
          fieldStrs.add(currentField);
          fieldCounter++;
        }
        TermInfo termInfo = indexEnum.termInfo();
        indexToTerms.set(i, dataOutput.getPosition());
        dataOutput.writeVInt(fieldCounter);
        dataOutput.writeString(term.text());
        dataOutput.writeVInt(termInfo.docFreq);
        if (termInfo.docFreq >= skipInterval) {
          dataOutput.writeVInt(termInfo.skipOffset);
        }
        dataOutput.writeVLong(termInfo.freqPointer);
        dataOutput.writeVLong(termInfo.proxPointer);
        dataOutput.writeVLong(indexEnum.indexPointer);
        for (int j = 1; j < indexDivisor; j++) {
          if (!indexEnum.next()) {
            break;
          }
        }
      }
  
      fields = new Term[fieldStrs.size()];
      for (int i = 0; i < fields.length; i++) {
        fields[i] = new Term(fieldStrs.get(i));
      }
      
      dataPagedBytes.freeze(true);
      dataInput = dataPagedBytes.getDataInput();
      indexToDataOffset = indexToTerms.getMutable();
    }
  
    private static int estimatePageBits(long estSize) {
      return Math.max(Math.min(64 - BitUtil.nlz(estSize), MAX_PAGE_BITS), 4);
    }
  
    public void seekEnum(SegmentTermEnum enumerator, int indexOffset) throws IOException {
      PagedBytesDataInput input = (PagedBytesDataInput) dataInput.clone();
      
      input.setPosition(indexToDataOffset.get(indexOffset));
  
      // read the term
      int fieldId = input.readVInt();
      Term field = fields[fieldId];
      Term term = field.createTerm(input.readString());
  
      // read the terminfo
      TermInfo termInfo = new TermInfo();
      termInfo.docFreq = input.readVInt();
      if (termInfo.docFreq >= skipInterval) {
        termInfo.skipOffset = input.readVInt();
      } else {
        termInfo.skipOffset = 0;
      }
      termInfo.freqPointer = input.readVLong();
      termInfo.proxPointer = input.readVLong();
  
      long pointer = input.readVLong();
  
      // perform the seek
      enumerator.seek(pointer, ((long) indexOffset * totalIndexInterval) - 1, term, termInfo);
    }
  
    /**
     * Binary search for the given term.
     * 
     * @param term
     *          the term to locate.
     * @throws IOException 
     */
    public int getIndexOffset(Term term, BytesRef termBytesRef) throws IOException {
      int lo = 0;
      int hi = indexSize - 1;
      PagedBytesDataInput input = (PagedBytesDataInput) dataInput.clone();
      BytesRef scratch = new BytesRef();
      while (hi >= lo) {
        int mid = (lo + hi) >>> 1;
        int delta = compareTo(term, termBytesRef, mid, input, scratch);
        if (delta < 0)
          hi = mid - 1;
        else if (delta > 0)
          lo = mid + 1;
        else
          return mid;
      }
      return hi;
    }
  
    /**
     * Gets the term at the given position.  For testing.
     * 
     * @param termIndex
     *          the position to read the term from the index.
     * @return the term.
     * @throws IOException
     */
    Term getTerm(int termIndex) throws IOException {
      PagedBytesDataInput input = (PagedBytesDataInput) dataInput.clone();
      input.setPosition(indexToDataOffset.get(termIndex));
  
      // read the term
      int fieldId = input.readVInt();
      Term field = fields[fieldId];
      return field.createTerm(input.readString());
    }
  
    /**
     * Returns the number of terms.
     * 
     * @return int.
     */
    public int length() {
      return indexSize;
    }
  
    /**
     * The compares the given term against the term in the index specified by the
     * term index. ie It returns negative N when term is less than index term;
     * 
     * @param term
     *          the given term.
     * @param termIndex
     *          the index of the of term to compare.
     * @return int.
     * @throws IOException 
     */
    public int compareTo(Term term, BytesRef termBytesRef, int termIndex) throws IOException {
      return compareTo(term, termBytesRef, termIndex, (PagedBytesDataInput) dataInput.clone(), new BytesRef());
    }
  
    /**
     * Compare the fields of the terms first, and if not equals return from
     * compare. If equal compare terms.
     * 
     * @param term
     *          the term to compare.
     * @param termIndex
     *          the position of the term in the input to compare
     * @param input
     *          the input buffer.
     * @return int.
     * @throws IOException 
     */
    private int compareTo(Term term, BytesRef termBytesRef, int termIndex, PagedBytesDataInput input, BytesRef reuse) throws IOException {
      // if term field does not equal mid's field index, then compare fields
      // else if they are equal, compare term's string values...
      int c = compareField(term, termIndex, input);
      if (c == 0) {
        reuse.length = input.readVInt();
        reuse.grow(reuse.length);
        input.readBytes(reuse.bytes, 0, reuse.length);
        return comparator.compare(termBytesRef, reuse);
      }
      return c;
    }
  
    /**
     * Compares the fields before checking the text of the terms.
     * 
     * @param term
     *          the given term.
     * @param termIndex
     *          the term that exists in the data block.
     * @param input
     *          the data block.
     * @return int.
     * @throws IOException 
     */
    private int compareField(Term term, int termIndex, PagedBytesDataInput input) throws IOException {
      input.setPosition(indexToDataOffset.get(termIndex));
      return term.field.compareTo(fields[input.readVInt()].field);
    }
  }
  