src/Lucene.Net.Codecs/BlockTerms/TermsIndexReaderBase.cs

using Lucene.Net.Index;
using Lucene.Net.Util;
using System;

namespace Lucene.Net.Codecs.BlockTerms
{
    /*
     * 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.
     */

    // TODO
    //   - allow for non-regular index intervals?  eg with a
    //     long string of rare terms, you don't need such
    //     frequent indexing

    /// <summary>
    /// <see cref="BlockTermsReader"/> interacts with an instance of this class
    /// to manage its terms index.  The writer must accept
    /// indexed terms (many pairs of <see cref="BytesRef"/> text + long
    /// fileOffset), and then this reader must be able to
    /// retrieve the nearest index term to a provided term
    /// text. 
    /// <para/>
    /// @lucene.experimental
    /// </summary>
    public abstract class TermsIndexReaderBase : IDisposable
    {
        public abstract FieldIndexEnum GetFieldEnum(FieldInfo fieldInfo);

        // LUCENENET specific - implementing proper dispose pattern
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        protected abstract void Dispose(bool disposing);

        public abstract bool SupportsOrd { get; }

        public abstract int Divisor { get; }

        /// <summary>
        /// Similar to <see cref="TermsEnum"/>, except, the only "metadata" it
        /// reports for a given indexed term is the long fileOffset
        /// into the main terms dictionary file.
        /// </summary>
        public abstract class FieldIndexEnum
        {
            /// <summary> 
            /// Seeks to "largest" indexed term that's less than or equal
            /// to term; returns file pointer index (into the main
            /// terms index file) for that term.
            /// </summary>
            public abstract long Seek(BytesRef term);

            /// <summary>Returns -1 at end/</summary>
            public abstract long Next();

            public abstract BytesRef Term { get; }

            /// <summary></summary>
            /// <remarks>Only implemented if <see cref="TermsIndexReaderBase.SupportsOrd"/>
            /// returns <c>true</c></remarks>
            /// <returns></returns>
            public abstract long Seek(long ord);

            /// <summary></summary>
            /// <remarks>Only implemented if <see cref="TermsIndexReaderBase.SupportsOrd"/> 
            /// returns <c>true</c></remarks>
            /// <returns></returns>
            public abstract long Ord { get; }
        }

        /// <summary>Returns approximate RAM bytes used.</summary>
        public abstract long RamBytesUsed();
    }
}