content: package org.apache.lucene.index.memory;
  
  /**
   * 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.io.Serializable;
  import java.io.StringReader;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Comparator;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.Iterator;
  import java.util.Map;
  
  import org.apache.lucene.analysis.Analyzer;
  import org.apache.lucene.analysis.TokenStream;
  import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
  import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
  import org.apache.lucene.analysis.tokenattributes.PositionIncrementAttribute;
  import org.apache.lucene.document.Document;
  import org.apache.lucene.document.FieldSelector;
  import org.apache.lucene.index.IndexReader;
  import org.apache.lucene.index.Term;
  import org.apache.lucene.index.TermDocs;
  import org.apache.lucene.index.TermEnum;
  import org.apache.lucene.index.TermFreqVector;
  import org.apache.lucene.index.TermPositionVector;
  import org.apache.lucene.index.TermPositions;
  import org.apache.lucene.index.TermVectorMapper;
  import org.apache.lucene.index.FieldInvertState;
  import org.apache.lucene.index.IndexReader.InvertParams;
  import org.apache.lucene.index.IndexReader.InvertResult;
  import org.apache.lucene.search.Collector;
  import org.apache.lucene.search.IndexSearcher;
  import org.apache.lucene.search.Query;
  import org.apache.lucene.search.Searcher;
  import org.apache.lucene.search.Scorer;
  import org.apache.lucene.search.Similarity;
  import org.apache.lucene.store.RAMDirectory; // for javadocs
  import org.apache.lucene.util.ArrayUtil;
  import org.apache.lucene.util.Constants; // for javadocs
  import org.apache.solr.schema.IndexSchema;
  
  /**
   * High-performance single-document main memory Apache Lucene fulltext search index. 
   * 
   * <h4>Overview</h4>
   * 
   * This class is a replacement/substitute for a large subset of
   * {@link RAMDirectory} functionality. It is designed to
   * enable maximum efficiency for on-the-fly matchmaking combining structured and 
   * fuzzy fulltext search in realtime streaming applications such as Nux XQuery based XML 
   * message queues, publish-subscribe systems for Blogs/newsfeeds, text chat, data acquisition and 
   * distribution systems, application level routers, firewalls, classifiers, etc. 
   * Rather than targeting fulltext search of infrequent queries over huge persistent 
   * data archives (historic search), this class targets fulltext search of huge 
   * numbers of queries over comparatively small transient realtime data (prospective 
   * search). 
   * For example as in 
   * <pre>
   * float score = search(String text, Query query)
   * </pre>
   * <p>
   * Each instance can hold at most one Lucene "document", with a document containing
   * zero or more "fields", each field having a name and a fulltext value. The
   * fulltext value is tokenized (split and transformed) into zero or more index terms 
   * (aka words) on <code>addField()</code>, according to the policy implemented by an
   * Analyzer. For example, Lucene analyzers can split on whitespace, normalize to lower case
   * for case insensitivity, ignore common terms with little discriminatory value such as "he", "in", "and" (stop
   * words), reduce the terms to their natural linguistic root form such as "fishing"
   * being reduced to "fish" (stemming), resolve synonyms/inflexions/thesauri 
   * (upon indexing and/or querying), etc. For details, see
   * <a target="_blank" href="http://today.java.net/pub/a/today/2003/07/30/LuceneIntro.html">Lucene Analyzer Intro</a>.
   * <p>
   * Arbitrary Lucene queries can be run against this class - see <a target="_blank" 
   * href="../../../../../../../queryparsersyntax.html">Lucene Query Syntax</a>
   * as well as <a target="_blank" 
   * href="http://today.java.net/pub/a/today/2003/11/07/QueryParserRules.html">Query Parser Rules</a>.
   * Note that a Lucene query selects on the field names and associated (indexed) 
   * tokenized terms, not on the original fulltext(s) - the latter are not stored 
   * but rather thrown away immediately after tokenization.
   * <p>
   * For some interesting background information on search technology, see Bob Wyman's
   * <a target="_blank" 
   * href="http://bobwyman.pubsub.com/main/2005/05/mary_hodder_poi.html">Prospective Search</a>, 
   * Jim Gray's
   * <a target="_blank" href="http://www.acmqueue.org/modules.php?name=Content&pa=showpage&pid=293&page=4">
   * A Call to Arms - Custom subscriptions</a>, and Tim Bray's
   * <a target="_blank" 
   * href="http://www.tbray.org/ongoing/When/200x/2003/07/30/OnSearchTOC">On Search, the Series</a>.
   * 
   * 
   * <h4>Example Usage</h4> 
   * 
   * <pre>
   * Analyzer analyzer = PatternAnalyzer.DEFAULT_ANALYZER;
   * //Analyzer analyzer = new SimpleAnalyzer();
   * MemoryIndex index = new MemoryIndex();
   * index.addField("content", "Readings about Salmons and other select Alaska fishing Manuals", analyzer);
   * index.addField("author", "Tales of James", analyzer);
   * QueryParser parser = new QueryParser("content", analyzer);
   * float score = index.search(parser.parse("+author:james +salmon~ +fish* manual~"));
   * if (score &gt; 0.0f) {
   *     System.out.println("it's a match");
   * } else {
   *     System.out.println("no match found");
   * }
   * System.out.println("indexData=" + index.toString());
   * </pre>
   * 
   * 
   * <h4>Example XQuery Usage</h4> 
   * 
   * <pre>
   * (: An XQuery that finds all books authored by James that have something to do with "salmon fishing manuals", sorted by relevance :)
   * declare namespace lucene = "java:nux.xom.pool.FullTextUtil";
   * declare variable $query := "+salmon~ +fish* manual~"; (: any arbitrary Lucene query can go here :)
   * 
   * for $book in /books/book[author="James" and lucene:match(abstract, $query) > 0.0]
   * let $score := lucene:match($book/abstract, $query)
   * order by $score descending
   * return $book
   * </pre>
   * 
   * 
   * <h4>No thread safety guarantees</h4>
   * 
   * An instance can be queried multiple times with the same or different queries,
   * but an instance is not thread-safe. If desired use idioms such as:
   * <pre>
   * MemoryIndex index = ...
   * synchronized (index) {
   *    // read and/or write index (i.e. add fields and/or query)
   * } 
   * </pre>
   * 
   * 
   * <h4>Performance Notes</h4>
   * 
   * Internally there's a new data structure geared towards efficient indexing 
   * and searching, plus the necessary support code to seamlessly plug into the Lucene 
   * framework.
   * <p>
   * This class performs very well for very small texts (e.g. 10 chars) 
   * as well as for large texts (e.g. 10 MB) and everything in between. 
   * Typically, it is about 10-100 times faster than <code>RAMDirectory</code>.
   * Note that <code>RAMDirectory</code> has particularly 
   * large efficiency overheads for small to medium sized texts, both in time and space.
   * Indexing a field with N tokens takes O(N) in the best case, and O(N logN) in the worst 
   * case. Memory consumption is probably larger than for <code>RAMDirectory</code>.
   * <p>
   * Example throughput of many simple term queries over a single MemoryIndex: 
   * ~500000 queries/sec on a MacBook Pro, jdk 1.5.0_06, server VM. 
   * As always, your mileage may vary.
   * <p>
   * If you're curious about
   * the whereabouts of bottlenecks, run java 1.5 with the non-perturbing '-server
   * -agentlib:hprof=cpu=samples,depth=10' flags, then study the trace log and
   * correlate its hotspot trailer with its call stack headers (see <a
   * target="_blank"
   * href="http://java.sun.com/developer/technicalArticles/Programming/HPROF.html">
   * hprof tracing </a>).
   *
   */
  public class MemoryIndex implements Serializable {
  
    /** info for each field: Map<String fieldName, Info field> */
    private final HashMap<String,Info> fields = new HashMap<String,Info>();
    
    /** fields sorted ascending by fieldName; lazily computed on demand */
    private transient Map.Entry<String,Info>[] sortedFields; 
    
    /** pos: positions[3*i], startOffset: positions[3*i +1], endOffset: positions[3*i +2] */
    private final int stride;
    
    /** Could be made configurable; See {@link Document#setBoost(float)} */
    private static final float docBoost = 1.0f;
    
    private static final long serialVersionUID = 2782195016849084649L;
  
    private static final boolean DEBUG = false;
    
    /**
     * Sorts term entries into ascending order; also works for
     * Arrays.binarySearch() and Arrays.sort()
     */
    private static final Comparator<Object> termComparator = new Comparator<Object>() {
      @SuppressWarnings("unchecked")
      public int compare(Object o1, Object o2) {
        if (o1 instanceof Map.Entry<?,?>) o1 = ((Map.Entry<?,?>) o1).getKey();
        if (o2 instanceof Map.Entry<?,?>) o2 = ((Map.Entry<?,?>) o2).getKey();
        if (o1 == o2) return 0;
        return ((String) o1).compareTo((String) o2);
      }
    };
  
    /**
     * Constructs an empty instance.
     */
    public MemoryIndex() {
      this(false);
    }
    
    /**
     * Constructs an empty instance that can optionally store the start and end
     * character offset of each token term in the text. This can be useful for
     * highlighting of hit locations with the Lucene highlighter package.
     * Private until the highlighter package matures, so that this can actually
     * be meaningfully integrated.
     * 
     * @param storeOffsets
     *            whether or not to store the start and end character offset of
     *            each token term in the text
     */
    private MemoryIndex(boolean storeOffsets) {
      this.stride = storeOffsets ? 3 : 1;
    }
    
    /**
     * Convenience method; Tokenizes the given field text and adds the resulting
     * terms to the index; Equivalent to adding an indexed non-keyword Lucene
     * {@link org.apache.lucene.document.Field} that is
     * {@link org.apache.lucene.document.Field.Index#ANALYZED tokenized},
     * {@link org.apache.lucene.document.Field.Store#NO not stored},
     * {@link org.apache.lucene.document.Field.TermVector#WITH_POSITIONS termVectorStored with positions} (or
     * {@link org.apache.lucene.document.Field.TermVector#WITH_POSITIONS termVectorStored with positions and offsets}),
     * 
     * @param fieldName
     *            a name to be associated with the text
     * @param text
     *            the text to tokenize and index.
     * @param analyzer
     *            the analyzer to use for tokenization
     */
    public void addField(String fieldName, String text, Analyzer analyzer) {
      if (fieldName == null)
        throw new IllegalArgumentException("fieldName must not be null");
      if (text == null)
        throw new IllegalArgumentException("text must not be null");
      if (analyzer == null)
        throw new IllegalArgumentException("analyzer must not be null");
      
      TokenStream stream;
      try {
        stream = analyzer.reusableTokenStream(fieldName, new StringReader(text));
      } catch (IOException ex) {
        throw new RuntimeException(ex);
      }
  
      addField(fieldName, stream);
    }
    
    /**
     * Convenience method; Creates and returns a token stream that generates a
     * token for each keyword in the given collection, "as is", without any
     * transforming text analysis. The resulting token stream can be fed into
     * {@link #addField(String, TokenStream)}, perhaps wrapped into another
     * {@link org.apache.lucene.analysis.TokenFilter}, as desired.
     * 
     * @param keywords
     *            the keywords to generate tokens for
     * @return the corresponding token stream
     */
    public <T> TokenStream keywordTokenStream(final Collection<T> keywords) {
      // TODO: deprecate & move this method into AnalyzerUtil?
      if (keywords == null)
        throw new IllegalArgumentException("keywords must not be null");
      
      return new TokenStream() {
        private Iterator<T> iter = keywords.iterator();
        private int start = 0;
        private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
        private final OffsetAttribute offsetAtt = addAttribute(OffsetAttribute.class);
        
        @Override
        public boolean incrementToken() {
          if (!iter.hasNext()) return false;
          
          T obj = iter.next();
          if (obj == null) 
            throw new IllegalArgumentException("keyword must not be null");
          
          String term = obj.toString();
          clearAttributes();
          termAtt.setEmpty().append(term);
          offsetAtt.setOffset(start, start+termAtt.length());
          start += term.length() + 1; // separate words by 1 (blank) character
          return true;
        }
      };
    }
    
    /**
     * Equivalent to <code>addField(fieldName, stream, 1.0f)</code>.
     * 
     * @param fieldName
     *            a name to be associated with the text
     * @param stream
     *            the token stream to retrieve tokens from
     */
    public void addField(String fieldName, TokenStream stream) {
      addField(fieldName, stream, 1.0f);
    }
  
    /**
     * Iterates over the given token stream and adds the resulting terms to the index;
     * Equivalent to adding a tokenized, indexed, termVectorStored, unstored,
     * Lucene {@link org.apache.lucene.document.Field}.
     * Finally closes the token stream. Note that untokenized keywords can be added with this method via 
     * {@link #keywordTokenStream(Collection)}, the Lucene contrib <code>KeywordTokenizer</code> or similar utilities.
     * 
     * @param fieldName
     *            a name to be associated with the text
     * @param stream
     *            the token stream to retrieve tokens from.
     * @param boost
     *            the boost factor for hits for this field
     * @see org.apache.lucene.document.Field#setBoost(float)
     */
    public void addField(String fieldName, TokenStream stream, float boost) {
      try {
        if (fieldName == null)
          throw new IllegalArgumentException("fieldName must not be null");
        if (stream == null)
            throw new IllegalArgumentException("token stream must not be null");
        if (boost <= 0.0f)
            throw new IllegalArgumentException("boost factor must be greater than 0.0");
        if (fields.get(fieldName) != null)
          throw new IllegalArgumentException("field must not be added more than once");
        
        HashMap<String,ArrayIntList> terms = new HashMap<String,ArrayIntList>();
        int numTokens = 0;
        int numOverlapTokens = 0;
        int pos = -1;
        
        CharTermAttribute termAtt = stream.addAttribute(CharTermAttribute.class);
        PositionIncrementAttribute posIncrAttribute = stream.addAttribute(PositionIncrementAttribute.class);
        OffsetAttribute offsetAtt = stream.addAttribute(OffsetAttribute.class);
        stream.reset();
        while (stream.incrementToken()) {
          String term = termAtt.toString();
          if (term.length() == 0) continue; // nothing to do
  //        if (DEBUG) System.err.println("token='" + term + "'");
          numTokens++;
          final int posIncr = posIncrAttribute.getPositionIncrement();
          if (posIncr == 0)
            numOverlapTokens++;
          pos += posIncr;
          
          ArrayIntList positions = terms.get(term);
          if (positions == null) { // term not seen before
            positions = new ArrayIntList(stride);
            terms.put(term, positions);
          }
          if (stride == 1) {
            positions.add(pos);
          } else {
            positions.add(pos, offsetAtt.startOffset(), offsetAtt.endOffset());
          }
        }
        stream.end();
  
        // ensure infos.numTokens > 0 invariant; needed for correct operation of terms()
        if (numTokens > 0) {
          boost = boost * docBoost; // see DocumentWriter.addDocument(...)
          fields.put(fieldName, new Info(terms, numTokens, numOverlapTokens, boost));
          sortedFields = null;    // invalidate sorted view, if any
        }
      } catch (IOException e) { // can never happen
        throw new RuntimeException(e);
      } finally {
        try {
          if (stream != null) stream.close();
        } catch (IOException e2) {
          throw new RuntimeException(e2);
        }
      }
    }
    
    /**
     * Creates and returns a searcher that can be used to execute arbitrary
     * Lucene queries and to collect the resulting query results as hits.
     * 
     * @return a searcher
     */
    public IndexSearcher createSearcher() {
      MemoryIndexReader reader = new MemoryIndexReader();
      IndexSearcher searcher = new IndexSearcher(reader); // ensures no auto-close !!
      reader.setSearcher(searcher); // to later get hold of searcher.getSimilarity()
      return searcher;
    }
    
    /**
     * Convenience method that efficiently returns the relevance score by
     * matching this index against the given Lucene query expression.
     * 
     * @param query
     *            an arbitrary Lucene query to run against this index
     * @return the relevance score of the matchmaking; A number in the range
     *         [0.0 .. 1.0], with 0.0 indicating no match. The higher the number
     *         the better the match.
     *
     */
    public float search(Query query) {
      if (query == null) 
        throw new IllegalArgumentException("query must not be null");
      
      Searcher searcher = createSearcher();
      try {
        final float[] scores = new float[1]; // inits to 0.0f (no match)
        searcher.search(query, new Collector() {
          private Scorer scorer;
  
          @Override
          public void collect(int doc) throws IOException {
            scores[0] = scorer.score();
          }
  
          @Override
          public void setScorer(Scorer scorer) throws IOException {
            this.scorer = scorer;
          }
  
          @Override
          public boolean acceptsDocsOutOfOrder() {
            return true;
          }
  
          @Override
          public void setNextReader(IndexReader reader, int docBase) { }
        });
        float score = scores[0];
        return score;
      } catch (IOException e) { // can never happen (RAMDirectory)
        throw new RuntimeException(e);
      } finally {
        // searcher.close();
        /*
         * Note that it is harmless and important for good performance to
         * NOT close the index reader!!! This avoids all sorts of
         * unnecessary baggage and locking in the Lucene IndexReader
         * superclass, all of which is completely unnecessary for this main
         * memory index data structure without thread-safety claims.
         * 
         * Wishing IndexReader would be an interface...
         * 
         * Actually with the new tight createSearcher() API auto-closing is now
         * made impossible, hence searcher.close() would be harmless and also 
         * would not degrade performance...
         */
      }   
    }
    
    /**
     * Returns a reasonable approximation of the main memory [bytes] consumed by
     * this instance. Useful for smart memory sensititive caches/pools. Assumes
     * fieldNames are interned, whereas tokenized terms are memory-overlaid.
     * 
     * @return the main memory consumption
     */
    public int getMemorySize() {
      // for example usage in a smart cache see nux.xom.pool.Pool    
      int PTR = VM.PTR;
      int INT = VM.INT;
      int size = 0;
      size += VM.sizeOfObject(2*PTR + INT); // memory index
      if (sortedFields != null) size += VM.sizeOfObjectArray(sortedFields.length);
      
      size += VM.sizeOfHashMap(fields.size());
      for (Map.Entry<String, Info> entry : fields.entrySet()) { // for each Field Info
        Info info = entry.getValue();
        size += VM.sizeOfObject(2*INT + 3*PTR); // Info instance vars
        if (info.sortedTerms != null) size += VM.sizeOfObjectArray(info.sortedTerms.length);
        
        int len = info.terms.size();
        size += VM.sizeOfHashMap(len);
        Iterator<Map.Entry<String,ArrayIntList>> iter2 = info.terms.entrySet().iterator();
        while (--len >= 0) { // for each term
          Map.Entry<String,ArrayIntList> e = iter2.next();
          size += VM.sizeOfObject(PTR + 3*INT); // assumes substring() memory overlay
  //        size += STR + 2 * ((String) e.getKey()).length();
          ArrayIntList positions = e.getValue();
          size += VM.sizeOfArrayIntList(positions.size());
        }
      }
      return size;
    } 
  
    private int numPositions(ArrayIntList positions) {
      return positions.size() / stride;
    }
    
    /** sorts into ascending order (on demand), reusing memory along the way */
    private void sortFields() {
      if (sortedFields == null) sortedFields = sort(fields);
    }
    
    /** returns a view of the given map's entries, sorted ascending by key */
    private static <K,V> Map.Entry<K,V>[] sort(HashMap<K,V> map) {
      int size = map.size();
      @SuppressWarnings("unchecked")
      Map.Entry<K,V>[] entries = new Map.Entry[size];
      
      Iterator<Map.Entry<K,V>> iter = map.entrySet().iterator();
      for (int i=0; i < size; i++) {
        entries[i] = iter.next();
      }
      
      if (size > 1) ArrayUtil.quickSort(entries, termComparator);
      return entries;
    }
    
    /**
     * Returns a String representation of the index data for debugging purposes.
     * 
     * @return the string representation
     */
    @Override
    public String toString() {
      StringBuilder result = new StringBuilder(256);    
      sortFields();   
      int sumChars = 0;
      int sumPositions = 0;
      int sumTerms = 0;
      
      for (int i=0; i < sortedFields.length; i++) {
        Map.Entry<String,Info> entry = sortedFields[i];
        String fieldName = entry.getKey();
        Info info = entry.getValue();
        info.sortTerms();
        result.append(fieldName + ":\n");
        
        int numChars = 0;
        int numPositions = 0;
        for (int j=0; j < info.sortedTerms.length; j++) {
          Map.Entry<String,ArrayIntList> e = info.sortedTerms[j];
          String term = e.getKey();
          ArrayIntList positions = e.getValue();
          result.append("\t'" + term + "':" + numPositions(positions) + ":");
          result.append(positions.toString(stride)); // ignore offsets
          result.append("\n");
          numPositions += numPositions(positions);
          numChars += term.length();
        }
        
        result.append("\tterms=" + info.sortedTerms.length);
        result.append(", positions=" + numPositions);
        result.append(", Kchars=" + (numChars/1000.0f));
        result.append("\n");
        sumPositions += numPositions;
        sumChars += numChars;
        sumTerms += info.sortedTerms.length;
      }
      
      result.append("\nfields=" + sortedFields.length);
      result.append(", terms=" + sumTerms);
      result.append(", positions=" + sumPositions);
      result.append(", Kchars=" + (sumChars/1000.0f));
      return result.toString();
    }
    
    
    ///////////////////////////////////////////////////////////////////////////////
    // Nested classes:
    ///////////////////////////////////////////////////////////////////////////////
    /**
     * Index data structure for a field; Contains the tokenized term texts and
     * their positions.
     */
    private static final class Info implements Serializable {
      
      /**
       * Term strings and their positions for this field: Map <String
       * termText, ArrayIntList positions>
       */
      private final HashMap<String,ArrayIntList> terms; 
      
      /** Terms sorted ascending by term text; computed on demand */
      private transient Map.Entry<String,ArrayIntList>[] sortedTerms;
      
      /** Number of added tokens for this field */
      private final int numTokens;
      
      /** Number of overlapping tokens for this field */
      private final int numOverlapTokens;
      
      /** Boost factor for hits for this field */
      private final float boost;
  
      /** Term for this field's fieldName, lazily computed on demand */
      public transient Term template;
  
      private static final long serialVersionUID = 2882195016849084649L;  
  
      public Info(HashMap<String,ArrayIntList> terms, int numTokens, int numOverlapTokens, float boost) {
        this.terms = terms;
        this.numTokens = numTokens;
        this.numOverlapTokens = numOverlapTokens;
        this.boost = boost;
      }
      
      /**
       * Sorts hashed terms into ascending order, reusing memory along the
       * way. Note that sorting is lazily delayed until required (often it's
       * not required at all). If a sorted view is required then hashing +
       * sort + binary search is still faster and smaller than TreeMap usage
       * (which would be an alternative and somewhat more elegant approach,
       * apart from more sophisticated Tries / prefix trees).
       */
      public void sortTerms() {
        if (sortedTerms == null) sortedTerms = sort(terms);
      }
          
      /** note that the frequency can be calculated as numPosition(getPositions(x)) */
      public ArrayIntList getPositions(String term) {
        return terms.get(term);
      }
  
      /** note that the frequency can be calculated as numPosition(getPositions(x)) */
      public ArrayIntList getPositions(int pos) {
        return sortedTerms[pos].getValue();
      }
      
      public float getBoost() {
        return boost;
      }
      
    }
    
    
    ///////////////////////////////////////////////////////////////////////////////
    // Nested classes:
    ///////////////////////////////////////////////////////////////////////////////
    /**
     * Efficient resizable auto-expanding list holding <code>int</code> elements;
     * implemented with arrays.
     */
    private static final class ArrayIntList implements Serializable {
  
      private int[] elements;
      private int size = 0;
      
      private static final long serialVersionUID = 2282195016849084649L;  
        
      public ArrayIntList() {
        this(10);
      }
  
      public ArrayIntList(int initialCapacity) {
        elements = new int[initialCapacity];
      }
  
      public void add(int elem) {
        if (size == elements.length) ensureCapacity(size + 1);
        elements[size++] = elem;
      }
  
      public void add(int pos, int start, int end) {
        if (size + 3 > elements.length) ensureCapacity(size + 3);
        elements[size] = pos;
        elements[size+1] = start;
        elements[size+2] = end;
        size += 3;
      }
  
      public int get(int index) {
        if (index >= size) throwIndex(index);
        return elements[index];
      }
      
      public int size() {
        return size;
      }
      
      public int[] toArray(int stride) {
        int[] arr = new int[size() / stride];
        if (stride == 1) {
          System.arraycopy(elements, 0, arr, 0, size); // fast path
        } else { 
          for (int i=0, j=0; j < size; i++, j += stride) arr[i] = elements[j];
        }
        return arr;
      }
      
      private void ensureCapacity(int minCapacity) {
        int newCapacity = Math.max(minCapacity, (elements.length * 3) / 2 + 1);
        int[] newElements = new int[newCapacity];
        System.arraycopy(elements, 0, newElements, 0, size);
        elements = newElements;
      }
  
      private void throwIndex(int index) {
        throw new IndexOutOfBoundsException("index: " + index
              + ", size: " + size);
      }
      
      /** returns the first few positions (without offsets); debug only */
      public String toString(int stride) {
        int s = size() / stride;
        int len = Math.min(10, s); // avoid printing huge lists
        StringBuilder buf = new StringBuilder(4*len);
        buf.append("[");
        for (int i = 0; i < len; i++) {
          buf.append(get(i*stride));
          if (i < len-1) buf.append(", ");
        }
        if (len != s) buf.append(", ..."); // and some more...
        buf.append("]");
        return buf.toString();
      }   
    }
    
    
    ///////////////////////////////////////////////////////////////////////////////
    // Nested classes:
    ///////////////////////////////////////////////////////////////////////////////
    private static final Term MATCH_ALL_TERM = new Term("");
      
    /**
     * Search support for Lucene framework integration; implements all methods
     * required by the Lucene IndexReader contracts.
     */
    private final class MemoryIndexReader extends IndexReader {
      
      private Searcher searcher; // needed to find searcher.getSimilarity() 
      
      private MemoryIndexReader() {
        super(); // avoid as much superclass baggage as possible
        readerFinishedListeners = Collections.synchronizedSet(new HashSet<ReaderFinishedListener>());
      }
      
      private Info getInfo(String fieldName) {
        return fields.get(fieldName);
      }
      
      private Info getInfo(int pos) {
        return sortedFields[pos].getValue();
      }
      
      @Override
      public int docFreq(Term term) {
        Info info = getInfo(term.field());
        int freq = 0;
        if (info != null) freq = info.getPositions(term.text()) != null ? 1 : 0;
        if (DEBUG) System.err.println("MemoryIndexReader.docFreq: " + term + ", freq:" + freq);
        return freq;
      }
    
      @Override
      public TermEnum terms() {
        if (DEBUG) System.err.println("MemoryIndexReader.terms()");
        return terms(MATCH_ALL_TERM);
      }
      
      @Override
      public TermEnum terms(Term term) {
        if (DEBUG) System.err.println("MemoryIndexReader.terms: " + term);
    
        int i; // index into info.sortedTerms
        int j; // index into sortedFields
        
        sortFields();
        if (sortedFields.length == 1 && sortedFields[0].getKey() == term.field()) {
          j = 0; // fast path
        } else {
          j = Arrays.binarySearch(sortedFields, term.field(), termComparator);
        }
        
        if (j < 0) { // not found; choose successor
          j = -j -1; 
          i = 0;
          if (j < sortedFields.length) getInfo(j).sortTerms();
        } else { // found
          Info info = getInfo(j);
          info.sortTerms();
          i = Arrays.binarySearch(info.sortedTerms, term.text(), termComparator);
          if (i < 0) { // not found; choose successor
            i = -i -1;
            if (i >= info.sortedTerms.length) { // move to next successor
              j++;
              i = 0;
              if (j < sortedFields.length) getInfo(j).sortTerms();
            }
          }
        }
        final int ix = i;
        final int jx = j;
    
        return new TermEnum() {
    
          private int srtTermsIdx = ix; // index into info.sortedTerms
          private int srtFldsIdx = jx; // index into sortedFields
            
          @Override
          public boolean next() {
            if (DEBUG) System.err.println("TermEnum.next");
            if (srtFldsIdx >= sortedFields.length) return false;
            Info info = getInfo(srtFldsIdx);
            if (++srtTermsIdx < info.sortedTerms.length) return true;
    
            // move to successor
            srtFldsIdx++;
            srtTermsIdx = 0;
            if (srtFldsIdx >= sortedFields.length) return false;
            getInfo(srtFldsIdx).sortTerms();
            return true;
          }
    
          @Override
          public Term term() {
            if (DEBUG) System.err.println("TermEnum.term: " + srtTermsIdx);
            if (srtFldsIdx >= sortedFields.length) return null;
            Info info = getInfo(srtFldsIdx);
            if (srtTermsIdx >= info.sortedTerms.length) return null;
  //          if (DEBUG) System.err.println("TermEnum.term: " + i + ", " + info.sortedTerms[i].getKey());
            return createTerm(info, srtFldsIdx, info.sortedTerms[srtTermsIdx].getKey());
          }
          
          @Override
          public int docFreq() {
            if (DEBUG) System.err.println("TermEnum.docFreq");
            if (srtFldsIdx >= sortedFields.length) return 0;
            Info info = getInfo(srtFldsIdx);
            if (srtTermsIdx >= info.sortedTerms.length) return 0;
            return numPositions(info.getPositions(srtTermsIdx));
          }
    
          @Override
          public void close() {
            if (DEBUG) System.err.println("TermEnum.close");
          }
          
          /** Returns a new Term object, minimizing String.intern() overheads. */
          private Term createTerm(Info info, int pos, String text) { 
            // Assertion: sortFields has already been called before
            Term template = info.template;
            if (template == null) { // not yet cached?
              String fieldName = sortedFields[pos].getKey();
              template = new Term(fieldName);
              info.template = template;
            }
            
            return template.createTerm(text);
          }
          
        };
      }
    
      @Override
      public TermPositions termPositions() {
        if (DEBUG) System.err.println("MemoryIndexReader.termPositions");
        
        return new TermPositions() {
    
          private boolean hasNext;
          private int cursor = 0;
          private ArrayIntList current;
          private Term term;
          
          public void seek(Term term) {
            this.term = term;
            if (DEBUG) System.err.println(".seek: " + term);
            if (term == null) {
              hasNext = true;  // term==null means match all docs
            } else {
              Info info = getInfo(term.field());
              current = info == null ? null : info.getPositions(term.text());
              hasNext = (current != null);
              cursor = 0;
            }
          }
    
          public void seek(TermEnum termEnum) {
            if (DEBUG) System.err.println(".seekEnum");
            seek(termEnum.term());
          }
    
          public int doc() {
            if (DEBUG) System.err.println(".doc");
            return 0;
          }
    
          public int freq() {
            int freq = current != null ? numPositions(current) : (term == null ? 1 : 0);
            if (DEBUG) System.err.println(".freq: " + freq);
            return freq;
          }
    
          public boolean next() {
            if (DEBUG) System.err.println(".next: " + current + ", oldHasNext=" + hasNext);
            boolean next = hasNext;
            hasNext = false;
            return next;
          }
    
          public int read(int[] docs, int[] freqs) {
            if (DEBUG) System.err.println(".read: " + docs.length);
            if (!hasNext) return 0;
            hasNext = false;
            docs[0] = 0;
            freqs[0] = freq();
            return 1;
          }
    
          public boolean skipTo(int target) {
            if (DEBUG) System.err.println(".skipTo: " + target);
            return next();
          }
    
          public void close() {
            if (DEBUG) System.err.println(".close");
          }
          
          public int nextPosition() { // implements TermPositions
            int pos = current.get(cursor);
            cursor += stride;
            if (DEBUG) System.err.println(".nextPosition: " + pos);
            return pos;
          }
          
          /**
           * Not implemented.
           * @throws UnsupportedOperationException
           */
          public int getPayloadLength() {
            throw new UnsupportedOperationException();
          }
           
          /**
           * Not implemented.
           * @throws UnsupportedOperationException
           */
          public byte[] getPayload(byte[] data, int offset) throws IOException {
            throw new UnsupportedOperationException();
          }
  
          public boolean isPayloadAvailable() {
            // unsuported
            return false;
          }
  
  		@Override
  		public void debug(StringBuffer buff) {
  			// TODO Auto-generated method stub
  			
  		}
  
        };
      }
    
      @Override
      public TermDocs termDocs(int buffer) {
        if (DEBUG) System.err.println("MemoryIndexReader.termDocs");
        return termPositions();
      }
    
      @Override
      public TermFreqVector[] getTermFreqVectors(int docNumber) {
        if (DEBUG) System.err.println("MemoryIndexReader.getTermFreqVectors");
        TermFreqVector[] vectors = new TermFreqVector[fields.size()];
  //      if (vectors.length == 0) return null;
        Iterator<String> iter = fields.keySet().iterator();
        for (int i=0; i < vectors.length; i++) {
          vectors[i] = getTermFreqVector(docNumber, iter.next());
        }
        return vectors;
      }
  
        @Override
        public void getTermFreqVector(int docNumber, TermVectorMapper mapper) throws IOException
        {
            if (DEBUG) System.err.println("MemoryIndexReader.getTermFreqVectors");
  
      //      if (vectors.length == 0) return null;
            for (final String fieldName : fields.keySet())
            {
              getTermFreqVector(docNumber, fieldName, mapper);
            }
        }
  
        @Override
        public void getTermFreqVector(int docNumber, String field, TermVectorMapper mapper) throws IOException
        {
          if (DEBUG) System.err.println("MemoryIndexReader.getTermFreqVector");
          final Info info = getInfo(field);
            if (info == null){
                return;
            }
            info.sortTerms();
            mapper.setExpectations(field, info.sortedTerms.length, stride != 1, true);
            for (int i = info.sortedTerms.length; --i >=0;){
  
                ArrayIntList positions = info.sortedTerms[i].getValue();
                int size = positions.size();
                org.apache.lucene.index.TermVectorOffsetInfo[] offsets =
                  new org.apache.lucene.index.TermVectorOffsetInfo[size / stride];
  
                for (int k=0, j=1; j < size; k++, j += stride) {
                  int start = positions.get(j);
                  int end = positions.get(j+1);
                  offsets[k] = new org.apache.lucene.index.TermVectorOffsetInfo(start, end);
                }
                mapper.map(info.sortedTerms[i].getKey(),
                           numPositions(info.sortedTerms[i].getValue()),
                           offsets, (info.sortedTerms[i].getValue()).toArray(stride));
            }
        }
  
        @Override
        public TermFreqVector getTermFreqVector(int docNumber, final String fieldName) {
        if (DEBUG) System.err.println("MemoryIndexReader.getTermFreqVector");
        final Info info = getInfo(fieldName);
        if (info == null) return null; // TODO: or return empty vector impl???
        info.sortTerms();
        
        return new TermPositionVector() { 
    
          private final Map.Entry<String,ArrayIntList>[] sortedTerms = info.sortedTerms;
          
          public String getField() {
            return fieldName;
          }
    
          public int size() {
            return sortedTerms.length;
          }
    
          public String[] getTerms() {
            String[] terms = new String[sortedTerms.length];
            for (int i=sortedTerms.length; --i >= 0; ) {
              terms[i] = sortedTerms[i].getKey();
            }
            return terms;
          }
    
          public int[] getTermFrequencies() {
            int[] freqs = new int[sortedTerms.length];
            for (int i=sortedTerms.length; --i >= 0; ) {
              freqs[i] = numPositions(sortedTerms[i].getValue());
            }
            return freqs;
          }
    
          public int indexOf(String term) {
            int i = Arrays.binarySearch(sortedTerms, term, termComparator);
            return i >= 0 ? i : -1;
          }
    
          public int[] indexesOf(String[] terms, int start, int len) {
            int[] indexes = new int[len];
            for (int i=0; i < len; i++) {
              indexes[i] = indexOf(terms[start++]);
            }
            return indexes;
          }
          
          // lucene >= 1.4.3
          public int[] getTermPositions(int index) {
            return sortedTerms[index].getValue().toArray(stride);
          } 
          
          // lucene >= 1.9 (remove this method for lucene-1.4.3)
          public org.apache.lucene.index.TermVectorOffsetInfo[] getOffsets(int index) {
            if (stride == 1) return null; // no offsets stored
            
            ArrayIntList positions = sortedTerms[index].getValue();
            int size = positions.size();
            org.apache.lucene.index.TermVectorOffsetInfo[] offsets = 
              new org.apache.lucene.index.TermVectorOffsetInfo[size / stride];
            
            for (int i=0, j=1; j < size; i++, j += stride) {
              int start = positions.get(j);
              int end = positions.get(j+1);
              offsets[i] = new org.apache.lucene.index.TermVectorOffsetInfo(start, end);
            }
            return offsets;
          }
  
        };
      }
  
      private Similarity getSimilarity() {
        if (searcher != null) return searcher.getSimilarity();
        return Similarity.getDefault();
      }
      
      private void setSearcher(Searcher searcher) {
        this.searcher = searcher;
      }
      
      /** performance hack: cache norms to avoid repeated expensive calculations */
      private byte[] cachedNorms;
      private String cachedFieldName;
      private Similarity cachedSimilarity;
      
      @Override
      public byte[] norms(String fieldName) {
        byte[] norms = cachedNorms;
        Similarity sim = getSimilarity();
        if (fieldName != cachedFieldName || sim != cachedSimilarity) { // not cached?
          Info info = getInfo(fieldName);
          int numTokens = info != null ? info.numTokens : 0;
          int numOverlapTokens = info != null ? info.numOverlapTokens : 0;
          float boost = info != null ? info.getBoost() : 1.0f; 
          FieldInvertState invertState = new FieldInvertState(0, numTokens, numOverlapTokens, 0, boost);
          float n = sim.computeNorm(fieldName, invertState);
          byte norm = sim.encodeNormValue(n);
          norms = new byte[] {norm};
          
          // cache it for future reuse
          cachedNorms = norms;
          cachedFieldName = fieldName;
          cachedSimilarity = sim;
          if (DEBUG) System.err.println("MemoryIndexReader.norms: " + fieldName + ":" + n + ":" + norm + ":" + numTokens);
        }
        return norms;
      }
    
      @Override
      public void norms(String fieldName, byte[] bytes, int offset) {
        if (DEBUG) System.err.println("MemoryIndexReader.norms*: " + fieldName);
        byte[] norms = norms(fieldName);
        System.arraycopy(norms, 0, bytes, offset, norms.length);
      }
    
      @Override
      protected void doSetNorm(int doc, String fieldName, byte value) {
        throw new UnsupportedOperationException();
      }
    
      @Override
      public int numDocs() {
        if (DEBUG) System.err.println("MemoryIndexReader.numDocs");
        return fields.size() > 0 ? 1 : 0;
      }
    
      @Override
      public int maxDoc() {
        if (DEBUG) System.err.println("MemoryIndexReader.maxDoc");
        return 1;
      }
    
      @Override
      public Document document(int n) {
        if (DEBUG) System.err.println("MemoryIndexReader.document");
        return new Document(); // there are no stored fields
      }
  
      //When we convert to JDK 1.5 make this Set<String>
      @Override
      public Document document(int n, FieldSelector fieldSelector) throws IOException {
        if (DEBUG) System.err.println("MemoryIndexReader.document");
        return new Document(); // there are no stored fields
      }
  
      @Override
      public boolean isDeleted(int n) {
        if (DEBUG) System.err.println("MemoryIndexReader.isDeleted");
        return false;
      }
    
      @Override
      public boolean hasDeletions() {
        if (DEBUG) System.err.println("MemoryIndexReader.hasDeletions");
        return false;
      }
      
      public InvertResult invertScan(IndexSchema schema, InvertParams params)throws Exception{
    	        throw new UnsupportedOperationException();
  
    	}
      
    
      @Override
      protected void doDelete(int docNum) {
        throw new UnsupportedOperationException();
      }
    
      @Override
      protected void doUndeleteAll() {
        throw new UnsupportedOperationException();
      }
    
      @Override
      protected void doCommit(Map<String,String> commitUserData) {
        if (DEBUG) System.err.println("MemoryIndexReader.doCommit");
      }
    
      @Override
      protected void doClose() {
        if (DEBUG) System.err.println("MemoryIndexReader.doClose");
      }
      
      // lucene >= 1.9 (remove this method for lucene-1.4.3)
      @Override
      public Collection<String> getFieldNames(FieldOption fieldOption) {
        if (DEBUG) System.err.println("MemoryIndexReader.getFieldNamesOption");
        if (fieldOption == FieldOption.UNINDEXED) 
          return Collections.<String>emptySet();
        if (fieldOption == FieldOption.INDEXED_NO_TERMVECTOR) 
          return Collections.<String>emptySet();
        if (fieldOption == FieldOption.TERMVECTOR_WITH_OFFSET && stride == 1) 
          return Collections.<String>emptySet();
        if (fieldOption == FieldOption.TERMVECTOR_WITH_POSITION_OFFSET && stride == 1) 
          return Collections.<String>emptySet();
        
        return Collections.unmodifiableSet(fields.keySet());
      }
  
  	@Override
  	public String getStringCacheKey() {
  		// TODO Auto-generated method stub
  		return this.getCoreCacheKey().toString();
  	}
  
  	@Override
  	public int getMaxInterval() throws Exception {
  		return 0;
  	}
    }
  
    
    ///////////////////////////////////////////////////////////////////////////////
    // Nested classes:
    ///////////////////////////////////////////////////////////////////////////////
    private static final class VM {
          
      public static final int PTR = Constants.JRE_IS_64BIT ? 8 : 4;    
  
      // bytes occupied by primitive data types
      public static final int BOOLEAN = 1;
      public static final int BYTE = 1;
      public static final int CHAR = 2;
      public static final int SHORT = 2;
      public static final int INT = 4;
      public static final int LONG = 8;
      public static final int FLOAT = 4;
      public static final int DOUBLE = 8;
      
      private static final int LOG_PTR = (int) Math.round(log2(PTR));
      
      /**
       * Object header of any heap allocated Java object. 
       * ptr to class, info for monitor, gc, hash, etc.
       */
      private static final int OBJECT_HEADER = 2*PTR; 
  
      private VM() {} // not instantiable
  
      //  assumes n > 0
      //  64 bit VM:
      //    0     --> 0*PTR
      //    1..8  --> 1*PTR
      //    9..16 --> 2*PTR
      private static int sizeOf(int n) {
          return (((n-1) >> LOG_PTR) + 1) << LOG_PTR;
      }
      
      public static int sizeOfObject(int n) {
          return sizeOf(OBJECT_HEADER + n);        
      }
      
      public static int sizeOfObjectArray(int len) {
          return sizeOfObject(INT + PTR*len);        
      }
      
      public static int sizeOfCharArray(int len) {
          return sizeOfObject(INT + CHAR*len);        
      }
      
      public static int sizeOfIntArray(int len) {
          return sizeOfObject(INT + INT*len);        
      }
      
      public static int sizeOfString(int len) {
          return sizeOfObject(3*INT + PTR) + sizeOfCharArray(len);
      }
      
      public static int sizeOfHashMap(int len) {
          return sizeOfObject(4*PTR + 4*INT) + sizeOfObjectArray(len) 
              + len * sizeOfObject(3*PTR + INT); // entries
      }
      
      // note: does not include referenced objects
      public static int sizeOfArrayList(int len) {
          return sizeOfObject(PTR + 2*INT) + sizeOfObjectArray(len); 
      }
      
      public static int sizeOfArrayIntList(int len) {
          return sizeOfObject(PTR + INT) + sizeOfIntArray(len);
      }
      
      /** logarithm to the base 2. Example: log2(4) == 2, log2(8) == 3 */
      private static double log2(double value) {
        return Math.log(value) / Math.log(2);
      }
          
    }
  
  }
  