src/Lucene.Net.Core/Index/IndexFileNameFilter.cs

/* 
 * 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.
 */

using System;
using System.Collections.Generic;

namespace Lucene.Net.Index
{
    
    /// <summary>Filename filter that accept filenames and extensions only created by Lucene. </summary>
    public class IndexFileNameFilter
    {
        
        private static IndexFileNameFilter singleton = new IndexFileNameFilter();
        private HashSet<String> extensions;
        private HashSet<String> extensionsInCFS;
        
        // Prevent instantiation.
        private IndexFileNameFilter()
        {
            extensions = new HashSet<String>();
            for (int i = 0; i < IndexFileNames.INDEX_EXTENSIONS.Length; i++)
            {
                extensions.Add(IndexFileNames.INDEX_EXTENSIONS[i]);
            }
            extensionsInCFS = new HashSet<String>();
            for (int i = 0; i < IndexFileNames.INDEX_EXTENSIONS_IN_COMPOUND_FILE.Length; i++)
            {
                extensionsInCFS.Add(IndexFileNames.INDEX_EXTENSIONS_IN_COMPOUND_FILE[i]);
            }
        }
        
        /* (non-Javadoc)
        * <see cref="java.io.FilenameFilter.accept(java.io.File, java.lang.String)"/>
        */
        public virtual bool Accept(System.IO.FileInfo dir, System.String name)
        {
            int i = name.LastIndexOf((System.Char) '.');
            if (i != - 1)
            {
                System.String extension = name.Substring(1 + i);
                if (extensions.Contains(extension))
                {
                    return true;
                }
                else if (extension.StartsWith("f") && (new System.Text.RegularExpressions.Regex("f\\d+")).Match(extension).Success)
                {
                    return true;
                }
                else if (extension.StartsWith("s") && (new System.Text.RegularExpressions.Regex("s\\d+")).Match(extension).Success)
                {
                    return true;
                }
            }
            else
            {
                if (name.Equals(IndexFileNames.DELETABLE))
                    return true;
                else if (name.StartsWith(IndexFileNames.SEGMENTS))
                    return true;
            }
            return false;
        }
        
        /// <summary> Returns true if this is a file that would be contained
        /// in a CFS file.  This function should only be called on
        /// files that pass the above "accept" (ie, are already
        /// known to be a Lucene index file).
        /// </summary>
        public virtual bool IsCFSFile(System.String name)
        {
            int i = name.LastIndexOf((System.Char) '.');
            if (i != - 1)
            {
                System.String extension = name.Substring(1 + i);
                if (extensionsInCFS.Contains(extension))
                {
                    return true;
                }
                if (extension.StartsWith("f") && (new System.Text.RegularExpressions.Regex("f\\d+")).Match(extension).Success)
                {
                    return true;
                }
            }
            return false;
        }

        public static IndexFileNameFilter Filter
        {
            get { return singleton; }
        }
    }
}