content: package org.apache.lucene.store;
  
  /**
   * 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.
   */
  
  import java.io.IOException;
  import java.util.zip.CRC32;
  import java.util.zip.Checksum;
  
  /** Writes bytes through to a primary IndexOutput, computing
   *  checksum as it goes. Note that you cannot use seek().
   *
   * @lucene.internal
   */
  public class ChecksumIndexInput extends IndexInput {
    IndexInput main;
    Checksum digest;
  
    public ChecksumIndexInput(IndexInput main) {
      super("ChecksumIndexInput(" + main + ")");
      this.main = main;
      digest = new CRC32();
    }
  
    @Override
    public byte readByte() throws IOException {
      final byte b = main.readByte();
      digest.update(b);
      return b;
    }
  
    @Override
    public void readBytes(byte[] b, int offset, int len)
      throws IOException {
      main.readBytes(b, offset, len);
      digest.update(b, offset, len);
    }
  
    
    public long getChecksum() {
      return digest.getValue();
    }
  
    @Override
    public void close() throws IOException {
      main.close();
    }
  
    @Override
    public long getFilePointer() {
      return main.getFilePointer();
    }
  
    @Override
    public void seek(long pos) {
      throw new RuntimeException("not allowed");
    }
  
    @Override
    public long length() {
      return main.length();
    }
  }
  