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C# / CSharp Open Source » Search Engines » dotLucene 
dotLucene » Lucene » Net » Index » IndexReader.cs
/*
 * Copyright 2004 The Apache Software Foundation
 * 
 * Licensed 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.
 */

using System;
using DocumentLucene.Net.Documents.Document;
using FieldLucene.Net.Documents.Field;
using SimilarityLucene.Net.Search.Similarity;
using DirectoryLucene.Net.Store.Directory;
using FSDirectoryLucene.Net.Store.FSDirectory;
using IndexInputLucene.Net.Store.IndexInput;
using LockLucene.Net.Store.Lock;

namespace Lucene.Net.Index{
  
  /// <summary>IndexReader is an abstract class, providing an interface for accessing an
  /// index.  Search of an index is done entirely through this abstract interface,
  /// so that any subclass which implements it is searchable.
  /// <p> Concrete subclasses of IndexReader are usually constructed with a call to
  /// one of the static <code>open()</code> methods, e.g. {@link #Open(String)}.
  /// <p> For efficiency, in this API documents are often referred to via
  /// <i>document numbers</i>, non-negative integers which each name a unique
  /// document in the index.  These document numbers are ephemeral--they may change
  /// as documents are added to and deleted from an index.  Clients should thus not
  /// rely on a given document having the same number between sessions.
  /// </summary>
  /// <summary><p> An IndexReader can be opened on a directory for which an IndexWriter is
  /// opened already, but it cannot be used to delete documents from the index then.
  /// </summary>
  /// <author>  Doug Cutting
  /// </author>
  /// <version>  $Id: IndexReader.java 354917 2005-12-08 00:22:00Z ehatcher $
  /// </version>
  public abstract class IndexReader
  {
    private class AnonymousClassWith : Lock.With
    {
      private void  InitBlock(Lucene.Net.Store.Directory directory, bool closeDirectory)
      {
        this.directory = directory;
        this.closeDirectory = closeDirectory;
      }
      private Lucene.Net.Store.Directory directory;
      private bool closeDirectory;
      internal AnonymousClassWith(Lucene.Net.Store.Directory directory, bool closeDirectory, Lucene.Net.Store.Lock Param1, long Param2):base(Param1, Param2)
      {
        InitBlock(directory, closeDirectory);
      }
      public override System.Object DoBody()
      {
        SegmentInfos infos = new SegmentInfos();
        infos.Read(directory);
        if (infos.Count == 1)
        {
          // index is optimized
          return SegmentReader.Get(infos, infos.Info(0), closeDirectory);
        }
        IndexReader[] readers = new IndexReader[infos.Count];
        for (int i = 0; i < infos.Count; i++)
          readers[i] = SegmentReader.Get(infos.Info(i));
        return new MultiReader(directory, infos, closeDirectory, readers);
      }
    }
    private class AnonymousClassWith1 : Lock.With
    {
      private void  InitBlock(IndexReader enclosingInstance)
      {
        this.enclosingInstance = enclosingInstance;
      }
      private IndexReader enclosingInstance;
      public IndexReader Enclosing_Instance
      {
        get
        {
          return enclosingInstance;
        }
        
      }
      internal AnonymousClassWith1(IndexReader enclosingInstance, Lucene.Net.Store.Lock Param1, long Param2) : base(Param1, Param2)
      {
        InitBlock(enclosingInstance);
      }
      public override System.Object DoBody()
      {
        Enclosing_Instance.DoCommit();
        Enclosing_Instance.segmentInfos.Write(Enclosing_Instance.directory);
        return null;
      }
    }
    
    public sealed class FieldOption
    {
      private System.String option;
      internal FieldOption()
      {
      }
      internal FieldOption(System.String option)
      {
        this.option = option;
      }
      public override System.String ToString()
      {
        return this.option;
      }
      // all fields
      public static readonly FieldOption ALL = new FieldOption("ALL");
      // all indexed fields
      public static readonly FieldOption INDEXED = new FieldOption("INDEXED");
      // all fields which are not indexed
      public static readonly FieldOption UNINDEXED = new FieldOption("UNINDEXED");
      // all fields which are indexed with termvectors enables
      public static readonly FieldOption INDEXED_WITH_TERMVECTOR = new FieldOption("INDEXED_WITH_TERMVECTOR");
      // all fields which are indexed but don't have termvectors enabled
      public static readonly FieldOption INDEXED_NO_TERMVECTOR = new FieldOption("INDEXED_NO_TERMVECTOR");
      // all fields where termvectors are enabled. Please note that only standard termvector fields are returned
      public static readonly FieldOption TERMVECTOR = new FieldOption("TERMVECTOR");
      // all field with termvectors wiht positions enabled
      public static readonly FieldOption TERMVECTOR_WITH_POSITION = new FieldOption("TERMVECTOR_WITH_POSITION");
      // all fields where termvectors with offset position are set
      public static readonly FieldOption TERMVECTOR_WITH_OFFSET = new FieldOption("TERMVECTOR_WITH_OFFSET");
      // all fields where termvectors with offset and position values set
      public static readonly FieldOption TERMVECTOR_WITH_POSITION_OFFSET = new FieldOption("TERMVECTOR_WITH_POSITION_OFFSET");
    }
    
    /// <summary> Constructor used if IndexReader is not owner of its directory. 
    /// This is used for IndexReaders that are used within other IndexReaders that take care or locking directories.
    /// 
    /// </summary>
    /// <param name="directory">Directory where IndexReader files reside.
    /// </param>
    protected internal IndexReader(Directory directory)
    {
      this.directory = directory;
    }
    
    /// <summary> Constructor used if IndexReader is owner of its directory.
    /// If IndexReader is owner of its directory, it locks its directory in case of write operations.
    /// 
    /// </summary>
    /// <param name="directory">Directory where IndexReader files reside.
    /// </param>
    /// <param name="segmentInfos">Used for write-l
    /// </param>
    /// <param name="closeDirectory">
    /// </param>
    internal IndexReader(Directory directory, SegmentInfos segmentInfos, bool closeDirectory)
    {
      Init(directory, segmentInfos, closeDirectory, true);
    }
    
    internal virtual void  Init(Directory directory, SegmentInfos segmentInfos, bool closeDirectory, bool directoryOwner)
    {
      this.directory = directory;
      this.segmentInfos = segmentInfos;
      this.directoryOwner = directoryOwner;
      this.closeDirectory = closeDirectory;
    }
    
    private Directory directory;
    private bool directoryOwner;
    private bool closeDirectory;
    
    private SegmentInfos segmentInfos;
    private Lock writeLock;
    private bool stale;
    private bool hasChanges;
    
    
    /// <summary>Returns an IndexReader reading the index in an FSDirectory in the named
    /// path. 
    /// </summary>
    public static IndexReader Open(System.String path)
    {
      return Open(FSDirectory.GetDirectory(path, false), true);
    }
    
    /// <summary>Returns an IndexReader reading the index in an FSDirectory in the named
    /// path. 
    /// </summary>
    public static IndexReader Open(System.IO.FileInfo path)
    {
      return Open(FSDirectory.GetDirectory(path, false), true);
    }
    
    /// <summary>Returns an IndexReader reading the index in the given Directory. </summary>
    public static IndexReader Open(Directory directory)
    {
      return Open(directory, false);
    }
    
    private static IndexReader Open(Directory directory, bool closeDirectory)
    {
      lock (directory)
      {
        // in- & inter-process sync
        return (IndexReader) new AnonymousClassWith(directory, closeDirectory, directory.MakeLock(IndexWriter.COMMIT_LOCK_NAME), IndexWriter.COMMIT_LOCK_TIMEOUT).Run();
      }
    }
    
    /// <summary>Returns the directory this index resides in. </summary>
    public virtual Directory Directory()
    {
      return directory;
    }
    
    /// <summary> Returns the time the index in the named directory was last modified.
    /// Do not use this to check whether the reader is still up-to-date, use
    /// {@link #IsCurrent()} instead. 
    /// </summary>
    public static long LastModified(System.String directory)
    {
      return LastModified(new System.IO.FileInfo(directory));
    }
    
    /// <summary> Returns the time the index in the named directory was last modified. 
    /// Do not use this to check whether the reader is still up-to-date, use
    /// {@link #IsCurrent()} instead. 
    /// </summary>
    public static long LastModified(System.IO.FileInfo directory)
    {
      return FSDirectory.FileModified(directory, IndexFileNames.SEGMENTS);
    }
    
    /// <summary> Returns the time the index in the named directory was last modified. 
    /// Do not use this to check whether the reader is still up-to-date, use
    /// {@link #IsCurrent()} instead. 
    /// </summary>
    public static long LastModified(Directory directory)
    {
      return directory.FileModified(IndexFileNames.SEGMENTS);
    }
    
    /// <summary> Reads version number from segments files. The version number is
    /// initialized with a timestamp and then increased by one for each change of
    /// the index.
    /// 
    /// </summary>
    /// <param name="directory">where the index resides.
    /// </param>
    /// <returns> version number.
    /// </returns>
    /// <throws>  IOException if segments file cannot be read </throws>
    public static long GetCurrentVersion(System.String directory)
    {
      return GetCurrentVersion(new System.IO.FileInfo(directory));
    }
    
    /// <summary> Reads version number from segments files. The version number is
    /// initialized with a timestamp and then increased by one for each change of
    /// the index.
    /// 
    /// </summary>
    /// <param name="directory">where the index resides.
    /// </param>
    /// <returns> version number.
    /// </returns>
    /// <throws>  IOException if segments file cannot be read </throws>
    public static long GetCurrentVersion(System.IO.FileInfo directory)
    {
      Directory dir = FSDirectory.GetDirectory(directory, false);
      long version = GetCurrentVersion(dir);
      dir.Close();
      return version;
    }
    
    /// <summary> Reads version number from segments files. The version number is
    /// initialized with a timestamp and then increased by one for each change of
    /// the index.
    /// 
    /// </summary>
    /// <param name="directory">where the index resides.
    /// </param>
    /// <returns> version number.
    /// </returns>
    /// <throws>  IOException if segments file cannot be read. </throws>
    public static long GetCurrentVersion(Directory directory)
    {
      return SegmentInfos.ReadCurrentVersion(directory);
    }
    
    /// <summary> Version number when this IndexReader was opened.</summary>
    public virtual long GetVersion()
    {
      return segmentInfos.GetVersion();
    }
    
    /// <summary> Check whether this IndexReader still works on a current version of the index.
    /// If this is not the case you will need to re-open the IndexReader to
    /// make sure you see the latest changes made to the index.
    /// 
    /// </summary>
    /// <throws>  IOException </throws>
    public virtual bool IsCurrent()
    {
      if (SegmentInfos.ReadCurrentVersion(directory) != segmentInfos.GetVersion())
      {
        return false;
      }
      return true;
    }
    
    /// <summary>  Return an array of term frequency vectors for the specified document.
    /// The array contains a vector for each vectorized field in the document.
    /// Each vector contains terms and frequencies for all terms in a given vectorized field.
    /// If no such fields existed, the method returns null. The term vectors that are
    /// returned my either be of type TermFreqVector or of type TermPositionsVector if
    /// positions or offsets have been stored.
    /// 
    /// </summary>
    /// <param name="docNumber">document for which term frequency vectors are returned
    /// </param>
    /// <returns> array of term frequency vectors. May be null if no term vectors have been
    /// stored for the specified document.
    /// </returns>
    /// <throws>  IOException if index cannot be accessed </throws>
    /// <seealso cref="Lucene.Net.document.Field.TermVector">
    /// </seealso>
    abstract public TermFreqVector[] GetTermFreqVectors(int docNumber);
    
    
    /// <summary>  Return a term frequency vector for the specified document and field. The
    /// returned vector contains terms and frequencies for the terms in
    /// the specified field of this document, if the field had the storeTermVector
    /// flag set. If termvectors had been stored with positions or offsets, a 
    /// TermPositionsVector is returned.
    /// 
    /// </summary>
    /// <param name="docNumber">document for which the term frequency vector is returned
    /// </param>
    /// <param name="field">field for which the term frequency vector is returned.
    /// </param>
    /// <returns> term frequency vector May be null if field does not exist in the specified
    /// document or term vector was not stored.
    /// </returns>
    /// <throws>  IOException if index cannot be accessed </throws>
    /// <seealso cref="Lucene.Net.document.Field.TermVector">
    /// </seealso>
    abstract public TermFreqVector GetTermFreqVector(int docNumber, System.String field);
    
    /// <summary> Returns <code>true</code> if an index exists at the specified directory.
    /// If the directory does not exist or if there is no index in it.
    /// <code>false</code> is returned.
    /// </summary>
    /// <param name="directory">the directory to check for an index
    /// </param>
    /// <returns> <code>true</code> if an index exists; <code>false</code> otherwise
    /// </returns>
    public static bool IndexExists(System.String directory)
    {
      bool tmpBool;
            if (System.IO.File.Exists((new System.IO.FileInfo(System.IO.Path.Combine(directory, IndexFileNames.SEGMENTS))).FullName))
        tmpBool = true;
      else
        tmpBool = System.IO.Directory.Exists((new System.IO.FileInfo(System.IO.Path.Combine(directory, IndexFileNames.SEGMENTS))).FullName);
      return tmpBool;
    }
    
    /// <summary> Returns <code>true</code> if an index exists at the specified directory.
    /// If the directory does not exist or if there is no index in it.
    /// </summary>
    /// <param name="directory">the directory to check for an index
    /// </param>
    /// <returns> <code>true</code> if an index exists; <code>false</code> otherwise
    /// </returns>
    public static bool IndexExists(System.IO.FileInfo directory)
    {
      bool tmpBool;
      if (System.IO.File.Exists((new System.IO.FileInfo(System.IO.Path.Combine(directory.FullName, IndexFileNames.SEGMENTS))).FullName))
        tmpBool = true;
      else
        tmpBool = System.IO.Directory.Exists((new System.IO.FileInfo(System.IO.Path.Combine(directory.FullName, IndexFileNames.SEGMENTS))).FullName);
      return tmpBool;
    }
    
    /// <summary> Returns <code>true</code> if an index exists at the specified directory.
    /// If the directory does not exist or if there is no index in it.
    /// </summary>
    /// <param name="directory">the directory to check for an index
    /// </param>
    /// <returns> <code>true</code> if an index exists; <code>false</code> otherwise
    /// </returns>
    /// <throws>  IOException if there is a problem with accessing the index </throws>
    public static bool IndexExists(Directory directory)
    {
      return directory.FileExists(IndexFileNames.SEGMENTS);
    }
    
    /// <summary>Returns the number of documents in this index. </summary>
    public abstract int NumDocs();
    
    /// <summary>Returns one greater than the largest possible document number.
    /// This may be used to, e.g., determine how big to allocate an array which
    /// will have an element for every document number in an index.
    /// </summary>
    public abstract int MaxDoc();
    
    /// <summary>Returns the stored fields of the <code>n</code><sup>th</sup>
    /// <code>Document</code> in this index. 
    /// </summary>
    public abstract Document Document(int n);
    
    /// <summary>Returns true if document <i>n</i> has been deleted </summary>
    public abstract bool IsDeleted(int n);
    
    /// <summary>Returns true if any documents have been deleted </summary>
    public abstract bool HasDeletions();
    
    /// <summary>Returns true if there are norms stored for this field. </summary>
    public virtual bool HasNorms(System.String field)
    {
      // backward compatible implementation.
      // SegmentReader has an efficient implementation.
      return Norms(field) != null;
    }
    
    /// <summary>Returns the byte-encoded normalization factor for the named field of
    /// every document.  This is used by the search code to score documents.
    /// 
    /// </summary>
    /// <seealso cref="Field.SetBoost(float)">
    /// </seealso>
    public abstract byte[] Norms(System.String field);
    
    /// <summary>Reads the byte-encoded normalization factor for the named field of every
    /// document.  This is used by the search code to score documents.
    /// 
    /// </summary>
    /// <seealso cref="Field.SetBoost(float)">
    /// </seealso>
    public abstract void  Norms(System.String field, byte[] bytes, int offset);
    
    /// <summary>Expert: Resets the normalization factor for the named field of the named
    /// document.  The norm represents the product of the field's {@link
    /// Field#SetBoost(float) boost} and its {@link Similarity#LengthNorm(String,
    /// int) length normalization}.  Thus, to preserve the length normalization
    /// values when resetting this, one should base the new value upon the old.
    /// 
    /// </summary>
    /// <seealso cref="Norms(String)">
    /// </seealso>
    /// <seealso cref="Similarity.DecodeNorm(byte)">
    /// </seealso>
    public void  SetNorm(int doc, System.String field, byte value_Renamed)
    {
      lock (this)
      {
        if (directoryOwner)
          AquireWriteLock();
        DoSetNorm(doc, field, value_Renamed);
        hasChanges = true;
      }
    }
    
    /// <summary>Implements setNorm in subclass.</summary>
    protected internal abstract void  DoSetNorm(int doc, System.String field, byte value_Renamed);
    
    /// <summary>Expert: Resets the normalization factor for the named field of the named
    /// document.
    /// 
    /// </summary>
    /// <seealso cref="Norms(String)">
    /// </seealso>
    /// <seealso cref="Similarity.DecodeNorm(byte)">
    /// </seealso>
    public virtual void  SetNorm(int doc, System.String field, float value_Renamed)
    {
      SetNorm(doc, field, Similarity.EncodeNorm(value_Renamed));
    }
    
    /// <summary>Returns an enumeration of all the terms in the index.
    /// The enumeration is ordered by Term.compareTo().  Each term
    /// is greater than all that precede it in the enumeration.
    /// </summary>
    public abstract TermEnum Terms();
    
    /// <summary>Returns an enumeration of all terms after a given term.
    /// The enumeration is ordered by Term.compareTo().  Each term
    /// is greater than all that precede it in the enumeration.
    /// </summary>
    public abstract TermEnum Terms(Term t);
    
    /// <summary>Returns the number of documents containing the term <code>t</code>. </summary>
    public abstract int DocFreq(Term t);
    
    /// <summary>Returns an enumeration of all the documents which contain
    /// <code>term</code>. For each document, the document number, the frequency of
    /// the term in that document is also provided, for use in search scoring.
    /// Thus, this method implements the mapping:
    /// <p><ul>
    /// Term &nbsp;&nbsp; =&gt; &nbsp;&nbsp; &lt;docNum, freq&gt;<sup>*</sup>
    /// </ul>
    /// <p>The enumeration is ordered by document number.  Each document number
    /// is greater than all that precede it in the enumeration.
    /// </summary>
    public virtual TermDocs TermDocs(Term term)
    {
      TermDocs termDocs = TermDocs();
      termDocs.Seek(term);
      return termDocs;
    }
    
    /// <summary>Returns an unpositioned {@link TermDocs} enumerator. </summary>
    public abstract TermDocs TermDocs();
    
    /// <summary>Returns an enumeration of all the documents which contain
    /// <code>term</code>.  For each document, in addition to the document number
    /// and frequency of the term in that document, a list of all of the ordinal
    /// positions of the term in the document is available.  Thus, this method
    /// implements the mapping:
    /// 
    /// <p><ul>
    /// Term &nbsp;&nbsp; =&gt; &nbsp;&nbsp; &lt;docNum, freq,
    /// &lt;pos<sub>1</sub>, pos<sub>2</sub>, ...
    /// pos<sub>freq-1</sub>&gt;
    /// &gt;<sup>*</sup>
    /// </ul>
    /// <p> This positional information faciliates phrase and proximity searching.
    /// <p>The enumeration is ordered by document number.  Each document number is
    /// greater than all that precede it in the enumeration.
    /// </summary>
    public virtual TermPositions TermPositions(Term term)
    {
      TermPositions termPositions = TermPositions();
      termPositions.Seek(term);
      return termPositions;
    }
    
    /// <summary>Returns an unpositioned {@link TermPositions} enumerator. </summary>
    public abstract TermPositions TermPositions();
    
    /// <summary> Tries to acquire the WriteLock on this directory.
    /// this method is only valid if this IndexReader is directory owner.
    /// 
    /// </summary>
    /// <throws>  IOException If WriteLock cannot be acquired. </throws>
    private void  AquireWriteLock()
    {
      if (stale)
        throw new System.IO.IOException("IndexReader out of date and no longer valid for delete, undelete, or setNorm operations");
      
      if (this.writeLock == null)
      {
        Lock writeLock = directory.MakeLock(IndexWriter.WRITE_LOCK_NAME);
        if (!writeLock.obtain(IndexWriter.WRITE_LOCK_TIMEOUT))
        // obtain write lock
        {
          throw new System.IO.IOException("Index locked for write: " + writeLock);
        }
        this.writeLock = writeLock;
        
        // we have to check whether index has changed since this reader was opened.
        // if so, this reader is no longer valid for deletion
        if (SegmentInfos.ReadCurrentVersion(directory) > segmentInfos.GetVersion())
        {
          stale = true;
          this.writeLock.Release();
          this.writeLock = null;
          throw new System.IO.IOException("IndexReader out of date and no longer valid for delete, undelete, or setNorm operations");
        }
      }
    }
    
    /// <summary>Deletes the document numbered <code>docNum</code>.  Once a document is
    /// deleted it will not appear in TermDocs or TermPostitions enumerations.
    /// Attempts to read its field with the {@link #document}
    /// method will result in an error.  The presence of this document may still be
    /// reflected in the {@link #docFreq} statistic, though
    /// this will be corrected eventually as the index is further modified.
    /// 
    /// </summary>
    /// <deprecated> Use {@link #DeleteDocument(int docNum)} instead.
    /// </deprecated>
    public void  Delete(int docNum)
    {
      lock (this)
      {
        DeleteDocument(docNum);
      }
    }
    
    /// <summary>Deletes the document numbered <code>docNum</code>.  Once a document is
    /// deleted it will not appear in TermDocs or TermPostitions enumerations.
    /// Attempts to read its field with the {@link #document}
    /// method will result in an error.  The presence of this document may still be
    /// reflected in the {@link #docFreq} statistic, though
    /// this will be corrected eventually as the index is further modified.
    /// </summary>
    //UPGRADE_NOTE: Synchronized keyword was removed from method 'DeleteDocument'. Lock expression was added. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1027'"
    public void  DeleteDocument(int docNum)
    {
      lock (this)
      {
        if (directoryOwner)
          AquireWriteLock();
        DoDelete(docNum);
        hasChanges = true;
      }
    }
    
    
    /// <summary>Implements deletion of the document numbered <code>docNum</code>.
    /// Applications should call {@link #Delete(int)} or {@link #Delete(Term)}.
    /// </summary>
    protected internal abstract void  DoDelete(int docNum);
    
    /// <summary>Deletes all documents containing <code>term</code>.
    /// This is useful if one uses a document field to hold a unique ID string for
    /// the document.  Then to delete such a document, one merely constructs a
    /// term with the appropriate field and the unique ID string as its text and
    /// passes it to this method.
    /// See {@link #Delete(int)} for information about when this deletion will
    /// become effective.
    /// </summary>
    /// <returns> the number of documents deleted
    /// 
    /// </returns>
    /// <deprecated> Use {@link #DeleteDocuments(Term term)} instead.
    /// </deprecated>
    public int Delete(Term term)
    {
      return DeleteDocuments(term);
    }
    
    /// <summary>Deletes all documents containing <code>term</code>.
    /// This is useful if one uses a document field to hold a unique ID string for
    /// the document.  Then to delete such a document, one merely constructs a
    /// term with the appropriate field and the unique ID string as its text and
    /// passes it to this method.
    /// See {@link #Delete(int)} for information about when this deletion will 
    /// become effective.
    /// </summary>
    /// <returns> the number of documents deleted
    /// </returns>
    public int DeleteDocuments(Term term)
    {
      TermDocs docs = TermDocs(term);
      if (docs == null)
        return 0;
      int n = 0;
      try
      {
        while (docs.Next())
        {
          DeleteDocument(docs.Doc());
          n++;
        }
      }
      finally
      {
        docs.Close();
      }
      return n;
    }
    
    /// <summary>Undeletes all documents currently marked as deleted in this index.</summary>
    public void  UndeleteAll()
    {
      lock (this)
      {
        if (directoryOwner)
          AquireWriteLock();
        DoUndeleteAll();
        hasChanges = true;
      }
    }
    
    /// <summary>Implements actual undeleteAll() in subclass. </summary>
    protected internal abstract void  DoUndeleteAll();
    
    /// <summary> Commit changes resulting from delete, undeleteAll, or setNorm operations
    /// 
    /// </summary>
    /// <throws>  IOException </throws>
    protected internal void  Commit()
    {
      lock (this)
      {
        if (hasChanges)
        {
          if (directoryOwner)
          {
            lock (directory)
            {
              // in- & inter-process sync
              new AnonymousClassWith1(this, directory.MakeLock(IndexWriter.COMMIT_LOCK_NAME), IndexWriter.COMMIT_LOCK_TIMEOUT).Run();
            }
            if (writeLock != null)
            {
              writeLock.Release(); // release write lock
              writeLock = null;
            }
          }
          else
            DoCommit();
        }
        hasChanges = false;
      }
    }
    
    /// <summary>Implements commit. </summary>
    protected internal abstract void  DoCommit();
    
    /// <summary> Closes files associated with this index.
    /// Also saves any new deletions to disk.
    /// No other methods should be called after this has been called.
    /// </summary>
    public void  Close()
    {
      lock (this)
      {
        Commit();
        DoClose();
        if (closeDirectory)
          directory.Close();
                System.GC.SuppressFinalize(this);
      }
    }
    
    /// <summary>Implements close. </summary>
    protected internal abstract void  DoClose();
    
    /// <summary>Release the write lock, if needed. </summary>
    ~IndexReader()
    {
      if (writeLock != null)
      {
        writeLock.Release(); // release write lock
        writeLock = null;
      }
    }
    
    /// <summary> Returns a list of all unique field names that exist in the index pointed
    /// to by this IndexReader.
    /// </summary>
    /// <returns> Collection of Strings indicating the names of the fields
    /// </returns>
    /// <throws>  IOException if there is a problem with accessing the index </throws>
    /// <summary> 
    /// </summary>
    /// <deprecated>  Replaced by {@link #GetFieldNames(IndexReader.FieldOption)}
    /// </deprecated>
    public abstract System.Collections.ICollection GetFieldNames();
    
    /// <summary> Returns a list of all unique field names that exist in the index pointed
    /// to by this IndexReader.  The boolean argument specifies whether the fields
    /// returned are indexed or not.
    /// </summary>
    /// <param name="indexed"><code>true</code> if only indexed fields should be returned;
    /// <code>false</code> if only unindexed fields should be returned.
    /// </param>
    /// <returns> Collection of Strings indicating the names of the fields
    /// </returns>
    /// <throws>  IOException if there is a problem with accessing the index </throws>
    /// <summary> 
    /// </summary>
    /// <deprecated>  Replaced by {@link #GetFieldNames(IndexReader.FieldOption)}
    /// </deprecated>
    public abstract System.Collections.ICollection GetFieldNames(bool indexed);
    
    /// <summary> </summary>
    /// <param name="storedTermVector">if true, returns only Indexed fields that have term vector info, 
    /// else only indexed fields without term vector info 
    /// </param>
    /// <returns> Collection of Strings indicating the names of the fields
    /// 
    /// </returns>
    /// <deprecated>  Replaced by {@link #GetFieldNames(IndexReader.FieldOption)}
    /// </deprecated>
    public virtual System.Collections.ICollection GetIndexedFieldNames(bool storedTermVector)
    {
      if (storedTermVector)
      {
        System.Collections.Hashtable fieldSet = new System.Collections.Hashtable();
                foreach (object item in GetIndexedFieldNames(Field.TermVector.YES))
                {
                    if (fieldSet.ContainsKey(item) == false)
                    {
                        fieldSet.Add(item, item);
                    }
                }
                foreach (object item in GetIndexedFieldNames(Field.TermVector.WITH_POSITIONS))
                {
                    if (fieldSet.ContainsKey(item) == false)
                    {
                        fieldSet.Add(item, item);
                    }
                }
                foreach (object item in GetIndexedFieldNames(Field.TermVector.WITH_OFFSETS))
                {
                    if (fieldSet.ContainsKey(item) == false)
                    {
                        fieldSet.Add(item, item);
                    }
                }
                foreach (object item in GetIndexedFieldNames(Field.TermVector.WITH_POSITIONS_OFFSETS))
                {
                    if (fieldSet.ContainsKey(item) == false)
                    {
                        fieldSet.Add(item, item);
                    }
                }
                return fieldSet;
      }
      else
        return GetIndexedFieldNames(Field.TermVector.NO);
    }
    
    /// <summary> Get a list of unique field names that exist in this index, are indexed, and have
    /// the specified term vector information.
    /// 
    /// </summary>
    /// <param name="tvSpec">specifies which term vector information should be available for the fields
    /// </param>
    /// <returns> Collection of Strings indicating the names of the fields
    /// 
    /// </returns>
    /// <deprecated>  Replaced by {@link #GetFieldNames(IndexReader.FieldOption)}
    /// </deprecated>
    public abstract System.Collections.ICollection GetIndexedFieldNames(Field.TermVector tvSpec);
    
    /// <summary> Get a list of unique field names that exist in this index and have the specified
    /// field option information.
    /// </summary>
    /// <param name="fldOption">specifies which field option should be available for the returned fields
    /// </param>
    /// <returns> Collection of Strings indicating the names of the fields.
    /// </returns>
    /// <seealso cref="IndexReader.FieldOption">
    /// </seealso>
    public abstract System.Collections.ICollection GetFieldNames(FieldOption fldOption);
    
    /// <summary> Returns <code>true</code> iff the index in the named directory is
    /// currently locked.
    /// </summary>
    /// <param name="directory">the directory to check for a lock
    /// </param>
    /// <throws>  IOException if there is a problem with accessing the index </throws>
    public static bool IsLocked(Directory directory)
    {
      return directory.MakeLock(IndexWriter.WRITE_LOCK_NAME).IsLocked() || directory.MakeLock(IndexWriter.COMMIT_LOCK_NAME).IsLocked();
    }
    
    /// <summary> Returns <code>true</code> iff the index in the named directory is
    /// currently locked.
    /// </summary>
    /// <param name="directory">the directory to check for a lock
    /// </param>
    /// <throws>  IOException if there is a problem with accessing the index </throws>
    public static bool IsLocked(System.String directory)
    {
      Directory dir = FSDirectory.GetDirectory(directory, false);
      bool result = IsLocked(dir);
      dir.Close();
      return result;
    }
    
    /// <summary> Forcibly unlocks the index in the named directory.
    /// <P>
    /// Caution: this should only be used by failure recovery code,
    /// when it is known that no other process nor thread is in fact
    /// currently accessing this index.
    /// </summary>
    public static void  Unlock(Directory directory)
    {
      directory.MakeLock(IndexWriter.WRITE_LOCK_NAME).Release();
      directory.MakeLock(IndexWriter.COMMIT_LOCK_NAME).Release();
    }
    
    /// <summary> Prints the filename and size of each file within a given compound file.
    /// Add the -extract flag to extract files to the current working directory.
    /// In order to make the extracted version of the index work, you have to copy
    /// the segments file from the compound index into the directory where the extracted files are stored.
    /// </summary>
    /// <param name="args">Usage: Lucene.Net.index.IndexReader [-extract] &lt;cfsfile&gt;
    /// </param>
    [STAThread]
    public static void  Main(System.String[] args)
    {
      System.String filename = null;
      bool extract = false;
      
      for (int i = 0; i < args.Length; ++i)
      {
        if (args[i].Equals("-extract"))
        {
          extract = true;
        }
        else if (filename == null)
        {
          filename = args[i];
        }
      }
      
      if (filename == null)
      {
        System.Console.Out.WriteLine("Usage: Lucene.Net.index.IndexReader [-extract] <cfsfile>");
        return ;
      }
      
      Directory dir = null;
      CompoundFileReader cfr = null;
      
      try
      {
        System.IO.FileInfo file = new System.IO.FileInfo(filename);
        System.String dirname = new System.IO.FileInfo(file.FullName).DirectoryName;
        filename = file.Name;
        dir = FSDirectory.GetDirectory(dirname, false);
        cfr = new CompoundFileReader(dir, filename);
        
        System.String[] files = cfr.List();
        System.Array.Sort(files); // sort the array of filename so that the output is more readable
        
        for (int i = 0; i < files.Length; ++i)
        {
          long len = cfr.FileLength(files[i]);
          
          if (extract)
          {
            System.Console.Out.WriteLine("extract " + files[i] + " with " + len + " bytes to local directory...");
            IndexInput ii = cfr.OpenInput(files[i]);
            
            System.IO.FileStream f = new System.IO.FileStream(files[i], System.IO.FileMode.Create);
            
            // read and write with a small buffer, which is more effectiv than reading byte by byte
            byte[] buffer = new byte[1024];
            int chunk = buffer.Length;
            while (len > 0)
            {
              int bufLen = (int) System.Math.Min(chunk, len);
              ii.ReadBytes(buffer, 0, bufLen);

                            byte[] byteArray = new byte[buffer.Length];
                            for (int index=0; index < buffer.Length; index++)
                                byteArray[index] = (byte) buffer[index];

                            f.Write(byteArray, 0, bufLen);

                            len -= bufLen;
            }
            
            f.Close();
            ii.Close();
          }
          else
            System.Console.Out.WriteLine(files[i] + ": " + len + " bytes");
        }
      }
      catch (System.IO.IOException ioe)
      {
        System.Console.Error.WriteLine(ioe.StackTrace);
      }
      finally
      {
        try
        {
          if (dir != null)
            dir.Close();
          if (cfr != null)
            cfr.Close();
        }
        catch (System.IO.IOException ioe)
        {
          System.Console.Error.WriteLine(ioe.StackTrace);
        }
      }
    }
  }
}
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