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   /*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project 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.jboss.netty.channel;
  
  import org.jboss.netty.logging.InternalLogger;
  import org.jboss.netty.logging.InternalLoggerFactory;
  
  import java.io.IOException;
  import java.nio.channels.FileChannel;
  import java.nio.channels.WritableByteChannel;
  
  public class DefaultFileRegion implements FileRegion {
  
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(DefaultFileRegion.class);
  
      private final FileChannel file;
      private final long position;
      private final long count;
      private final boolean releaseAfterTransfer;
  
      public DefaultFileRegion(FileChannel file, long position, long count) {
          this(file, position, count, false);
      }
  
      public DefaultFileRegion(FileChannel file, long position, long count, boolean releaseAfterTransfer) {
          this.file = file;
          this.position = position;
          this.count = count;
          this.releaseAfterTransfer = releaseAfterTransfer;
      }
  
      public long getPosition() {
          return position;
      }
  
      public long getCount() {
          return count;
      }
  
      public boolean releaseAfterTransfer() {
          return releaseAfterTransfer;
      }
  
      public long transferTo(WritableByteChannel target, long position) throws IOException {
          long count = this.count - position;
          if (count < 0 || position < 0) {
              throw new IllegalArgumentException(
                      "position out of range: " + position +
                      " (expected: 0 - " + (this.count - 1) + ')');
          }
          if (count == 0) {
              return 0L;
          }
  
          return file.transferTo(this.position + position, count, target);
      }
  
      public void releaseExternalResources() {
          try {
              file.close();
          } catch (IOException e) {
              if (logger.isWarnEnabled()) {
                  logger.warn("Failed to close a file.", e);
              }
          }
      }
  }