DocIdSet.cs

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/* 
 * 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;

namespace Lucene.Net.Search
{
    
    /// <summary> A DocIdSet contains a set of doc ids. Implementing classes must
    /// only implement <see cref="Iterator" /> to provide access to the set. 
    /// </summary>
    [Serializable]
    public abstract class DocIdSet
    {
        public class AnonymousClassDocIdSet:DocIdSet
        {
            public AnonymousClassDocIdSet()
            {
                InitBlock();
            }
            public class AnonymousClassDocIdSetIterator:DocIdSetIterator
            {
                public AnonymousClassDocIdSetIterator(AnonymousClassDocIdSet enclosingInstance)
                {
                    InitBlock(enclosingInstance);
                }
                private void  InitBlock(AnonymousClassDocIdSet enclosingInstance)
                {
                    this.enclosingInstance = enclosingInstance;
                }
                private AnonymousClassDocIdSet enclosingInstance;
                public AnonymousClassDocIdSet Enclosing_Instance
                {
                    get
                    {
                        return enclosingInstance;
                    }
                    
                }
                public override int Advance(int target)
                {
                    return NO_MORE_DOCS;
                }
                public override int DocID()
                {
                    return NO_MORE_DOCS;
                }
                public override int NextDoc()
                {
                    return NO_MORE_DOCS;
                }
            }
            private void  InitBlock()
            {
                iterator = new AnonymousClassDocIdSetIterator(this);
            }
            
            private DocIdSetIterator iterator;
            
            public override DocIdSetIterator Iterator()
            {
                return iterator;
            }

            public override bool IsCacheable
            {
                get { return true; }
            }
        }

        /// <summary>An empty <see cref="DocIdSet"/> instance for easy use, e.g. in Filters that hit no documents. </summary>
        [NonSerialized]
        public static readonly DocIdSet EMPTY_DOCIDSET;
        
        /// <summary>Provides a <see cref="DocIdSetIterator" /> to access the set.
        /// This implementation can return <c>null</c> or
        /// <c>EMPTY_DOCIDSET.Iterator()</c> if there
        /// are no docs that match. 
        /// </summary>
        public abstract DocIdSetIterator Iterator();

        /// <summary>This method is a hint for <see cref="CachingWrapperFilter" />, if this <c>DocIdSet</c>
        /// should be cached without copying it into a BitSet. The default is to return
        /// <c>false</c>. If you have an own <c>DocIdSet</c> implementation
        /// that does its iteration very effective and fast without doing disk I/O,
        /// override this method and return true.
        /// </summary>
        public virtual bool IsCacheable
        {
            get { return false; }
        }

        static DocIdSet()
        {
            EMPTY_DOCIDSET = new AnonymousClassDocIdSet();
        }
    }
}