CheckSumIndexInput.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;
using Lucene.Net.Support;

namespace Lucene.Net.Store
{
    
    /// <summary>Writes bytes through to a primary IndexOutput, computing
    /// checksum as it goes. Note that you cannot use seek(). 
    /// </summary>
    public class ChecksumIndexInput : IndexInput
    {
        internal IndexInput main;
        internal IChecksum digest;

        private bool isDisposed;
        
        public ChecksumIndexInput(IndexInput main)
        {
            this.main = main;
            digest = new CRC32();
        }
        
        public override byte ReadByte()
        {
            byte b = main.ReadByte();
            digest.Update(b);
            return b;
        }
        
        public override void  ReadBytes(byte[] b, int offset, int len)
        {
            main.ReadBytes(b, offset, len);
            digest.Update(b, offset, len);
        }

        public virtual long Checksum
        {
            get { return digest.Value; }
        }

        protected override void Dispose(bool disposing)
        {
            if (isDisposed) return;

            if (disposing)
            {
                if (main != null)
                {
                    main.Dispose();
                }
            }

            main = null;
            isDisposed = true;
        }

        public override long FilePointer
        {
            get { return main.FilePointer; }
        }

        public override void  Seek(long pos)
        {
            throw new System.SystemException("not allowed");
        }
        
        public override long Length()
        {
            return main.Length();
        }
    }
}