Add --enable-deletion option to buildindex. If used, buildindex will remove deleted...

[beagle.git] / beagled / 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 Document = Lucene.Net.Documents.Document;
using Field = Lucene.Net.Documents.Field;
using Similarity = Lucene.Net.Search.Similarity;
using Directory = Lucene.Net.Store.Directory;
using FSDirectory = Lucene.Net.Store.FSDirectory;
using IndexInput = Lucene.Net.Store.IndexInput;
using Lock = Lucene.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>
    /// <author>  Doug Cutting
    /// </author>
    /// <version>  $Id: IndexReader.cs,v 1.3 2005/10/06 19:29:55 dsd Exp $
    /// </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. 
                /// 
                /// <p>Synchronization of IndexReader and IndexWriter instances is 
                /// no longer done via time stamps of the segments file since the time resolution 
                /// depends on the hardware platform. Instead, a version number is maintained
                /// within the segments file, which is incremented everytime when the index is
                /// changed.</p>
                /// 
                /// </summary>
                /// <deprecated>  Replaced by {@link #GetCurrentVersion(String)}
                /// 
                /// </deprecated>
                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. 
                /// 
                /// <p>Synchronization of IndexReader and IndexWriter instances is 
                /// no longer done via time stamps of the segments file since the time resolution 
                /// depends on the hardware platform. Instead, a version number is maintained
                /// within the segments file, which is incremented everytime when the index is
                /// changed.</p>
                /// 
                /// </summary>
                /// <deprecated>  Replaced by {@link #GetCurrentVersion(File)}
                /// 
                /// </deprecated>
                public static long LastModified(System.IO.FileInfo directory)
                {
                        return FSDirectory.FileModified(directory, "segments");
                }
                
                /// <summary> Returns the time the index in the named directory was last modified. 
                /// 
                /// <p>Synchronization of IndexReader and IndexWriter instances is 
                /// no longer done via time stamps of the segments file since the time resolution 
                /// depends on the hardware platform. Instead, a version number is maintained
                /// within the segments file, which is incremented everytime when the index is
                /// changed.</p>
                /// 
                /// </summary>
                /// <deprecated>  Replaced by {@link #GetCurrentVersion(Directory)}
                /// 
                /// </deprecated>
                public static long LastModified(Directory directory)
                {
                        return directory.FileModified("segments");
                }
                
                /// <summary> Reads version number from segments files. The version number counts the
                /// number of changes 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 counts the
                /// number of changes 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 counts the
                /// number of changes 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>  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, "segments"))).FullName))
                                tmpBool = true;
                        else
                                tmpBool = System.IO.Directory.Exists((new System.IO.FileInfo(System.IO.Path.Combine(directory, "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, "segments"))).FullName))
                                tmpBool = true;
                        else
                                tmpBool = System.IO.Directory.Exists((new System.IO.FileInfo(System.IO.Path.Combine(directory.FullName, "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("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 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>
                public void  Delete(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.  Returns the number of documents deleted.
        /// See {@link #Delete(int)} for information about when this deletion will 
        /// become effective.
        /// </summary>
                public int Delete(Term term)
                {
                        TermDocs docs = TermDocs(term);
                        if (docs == null)
                                return 0;
                        int n = 0;
                        try
                        {
                                while (docs.Next())
                                {
                                        Delete(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
        /// </param>
        [STAThread]
        public static void  Main(System.String[] args)
        {
            System.String dirname = null, filename = null;
            bool extract = false;
                        
            for (int i = 0; i < args.Length; ++i)
            {
                if (args[i].Equals("-extract"))
                {
                    extract = true;
                }
                else if (dirname == null)
                {
                    dirname = args[i];
                }
                else if (filename == null)
                {
                    filename = args[i];
                }
            }
                        
            if (dirname == null || filename == null)
            {
                System.Console.Out.WriteLine("Usage: Lucene.Net.index.IndexReader [-extract] <directory> <cfsfile>");
                return ;
            }
                        
            Directory dir = null;
            CompoundFileReader cfr = null;
                        
            try
            {
                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);
                }
            }
        }
    }
}