content: /*
   * 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.
   */
  package org.apache.bookkeeper.bookie;
  
  import java.io.IOException;
  import java.nio.channels.FileChannel;
  
  /**
   * A {@code BufferedChannelBase} adds functionality to an existing file channel, the ability
   * to buffer the input and output data. This class is a base class for wrapping the {@link FileChannel}.
   */
  public abstract class BufferedChannelBase {
      static class BufferedChannelClosedException extends IOException {
          BufferedChannelClosedException() {
              super("Attempting to access a file channel that has already been closed");
          }
      }
  
      protected final FileChannel fileChannel;
  
      protected BufferedChannelBase(FileChannel fc) {
          this.fileChannel = fc;
      }
  
      protected FileChannel validateAndGetFileChannel() throws IOException {
          // Even if we have BufferedChannelBase objects in the cache, higher layers should
          // guarantee that once a log file has been closed and possibly deleted during garbage
          // collection, attempts will not be made to read from it
          if (!fileChannel.isOpen()) {
              throw new BufferedChannelClosedException();
          }
          return fileChannel;
      }
  
      /**
       * Get the current size of the underlying FileChannel.
       * @return
       */
      public long size() throws IOException {
          return validateAndGetFileChannel().size();
      }
  
  }
  