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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:
    *
    *   https://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 io.netty.channel;
  
  import io.netty.util.AbstractReferenceCounted;
  import io.netty.util.IllegalReferenceCountException;
  import io.netty.util.internal.ObjectUtil;
  import io.netty.util.internal.logging.InternalLogger;
  import io.netty.util.internal.logging.InternalLoggerFactory;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.RandomAccessFile;
  import java.nio.channels.FileChannel;
  import java.nio.channels.WritableByteChannel;
  
  import static io.netty.util.internal.ObjectUtil.checkPositiveOrZero;
  
  /**
   * Default {@link FileRegion} implementation which transfer data from a {@link FileChannel} or {@link File}.
   *
   * Be aware that the {@link FileChannel} will be automatically closed once {@link #refCnt()} returns
   * {@code 0}.
   */
  public class DefaultFileRegion extends AbstractReferenceCounted implements FileRegion {
  
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(DefaultFileRegion.class);
      private final File f;
      private final long position;
      private final long count;
      private long transferred;
      private FileChannel file;
  
      /**
       * Create a new instance
       *
       * @param fileChannel      the {@link FileChannel} which should be transferred
       * @param position         the position from which the transfer should start
       * @param count            the number of bytes to transfer
       */
      public DefaultFileRegion(FileChannel fileChannel, long position, long count) {
          this.file = ObjectUtil.checkNotNull(fileChannel, "fileChannel");
          this.position = checkPositiveOrZero(position, "position");
          this.count = checkPositiveOrZero(count, "count");
          this.f = null;
      }
  
      /**
       * Create a new instance using the given {@link File}. The {@link File} will be opened lazily or
       * explicitly via {@link #open()}.
       *
       * @param file         the {@link File} which should be transferred
       * @param position     the position from which the transfer should start
       * @param count        the number of bytes to transfer
       */
      public DefaultFileRegion(File file, long position, long count) {
          this.f = ObjectUtil.checkNotNull(file, "file");
          this.position = checkPositiveOrZero(position, "position");
          this.count = checkPositiveOrZero(count, "count");
      }
  
      /**
       * Returns {@code true} if the {@link FileRegion} has a open file-descriptor
       */
      public boolean isOpen() {
          return file != null;
      }
  
      /**
       * Explicitly open the underlying file-descriptor if not done yet.
       */
      public void open() throws IOException {
          if (!isOpen() && refCnt() > 0) {
              // Only open if this DefaultFileRegion was not released yet.
              file = new RandomAccessFile(f, "r").getChannel();
          }
      }
  
      @Override
      public long position() {
          return position;
      }
  
      @Override
      public long count() {
          return count;
     }
 
     @Deprecated
     @Override
     public long transfered() {
         return transferred;
     }
 
     @Override
     public long transferred() {
         return transferred;
     }
 
     @Override
     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;
         }
         if (refCnt() == 0) {
             throw new IllegalReferenceCountException(0);
         }
         // Call open to make sure fc is initialized. This is a no-oop if we called it before.
         open();
 
         long written = file.transferTo(this.position + position, count, target);
         if (written > 0) {
             transferred += written;
         } else if (written == 0) {
             // If the amount of written data is 0 we need to check if the requested count is bigger then the
             // actual file itself as it may have been truncated on disk.
             //
             // See https://github.com/netty/netty/issues/8868
             validate(this, position);
         }
         return written;
     }
 
     @Override
     protected void deallocate() {
         FileChannel file = this.file;
 
         if (file == null) {
             return;
         }
         this.file = null;
 
         try {
             file.close();
         } catch (IOException e) {
             logger.warn("Failed to close a file.", e);
         }
     }
 
     @Override
     public FileRegion retain() {
         super.retain();
         return this;
     }
 
     @Override
     public FileRegion retain(int increment) {
         super.retain(increment);
         return this;
     }
 
     @Override
     public FileRegion touch() {
         return this;
     }
 
     @Override
     public FileRegion touch(Object hint) {
         return this;
     }
 
     static void validate(DefaultFileRegion region, long position) throws IOException {
         // If the amount of written data is 0 we need to check if the requested count is bigger then the
         // actual file itself as it may have been truncated on disk.
         //
         // See https://github.com/netty/netty/issues/8868
         long size = region.file.size();
         long count = region.count - position;
         if (region.position + count + position > size) {
             throw new IOException("Underlying file size " + size + " smaller then requested count " + region.count);
         }
     }
 }