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    1   /*
    2    * Copyright 2010 Red Hat, Inc.
    3    *
    4    * Red Hat licenses this file to you under the Apache License, version 2.0
    5    * (the "License"); you may not use this file except in compliance with the
    6    * License.  You may obtain a copy of the License at:
    7    *
    8    *    http://www.apache.org/licenses/LICENSE-2.0
    9    *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
    12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
    13   * License for the specific language governing permissions and limitations
    14   * under the License.
    15   */
    16  package org.jboss.netty.channel;
    17
    18  import java.io.IOException;
    19  import java.nio.channels.FileChannel;
    20  import java.nio.channels.WritableByteChannel;
    21
    22  import org.jboss.netty.util.ExternalResourceReleasable;
    23
    24  /**
    25   * A region of a file that is sent via a {@link Channel} which supports
    26   * <a href="http://en.wikipedia.org/wiki/Zero-copy">zero-copy file transfer</a>.
    27   *
    28   * <h3>Upgrade your JDK / JRE</h3>
    29   *
    30   * {@link FileChannel#transferTo(long, long, WritableByteChannel)} has at least
    31   * four known bugs in the old versions of Sun JDK and perhaps its derived ones.
    32   * Please upgrade your JDK to 1.6.0_18 or later version if you are going to use
    33   * zero-copy file transfer.
    34   * <ul>
    35   * <li><a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=5103988">5103988</a>
    36   *   - FileChannel.transferTo() should return -1 for EAGAIN instead throws IOException</li>
    37   * <li><a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6253145">6253145</a>
    38   *   - FileChannel.transferTo() on Linux fails when going beyond 2GB boundary</li>
    39   * <li><a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6427312">6427312</a>
    40   *   - FileChannel.transferTo() throws IOException "system call interrupted"</li>
    41   * <li><a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6524172">6470086</a>
    42   *   - FileChannel.transferTo(2147483647, 1, channel) causes "Value too large" exception</li>
    43   * </ul>
    44   *
    45   * <h3>Check your operating system and JDK / JRE</h3>
    46   *
    47   * If your operating system (or JDK / JRE) does not support zero-copy file
    48   * transfer, sending a file with {@link FileRegion} might fail or yield worse
    49   * performance.  For example, sending a large file doesn't work well in Windows.
    50   *
    51   * @author <a href="http://www.jboss.org/netty/">The Netty Project</a>
    52   * @author <a href="http://gleamynode.net/">Trustin Lee</a>
    53   * @version $Rev: 2080 $, $Date: 2010-01-26 18:04:19 +0900 (Tue, 26 Jan 2010) $
    54   */
    55  public interface FileRegion extends ExternalResourceReleasable {
    56
    57      /**
    58       * Returns the offset in the file where the transfer began.
    59       */
    60      long getPosition();
    61
    62      /**
    63       * Returns the number of bytes to transfer.
    64       */
    65      long getCount();
    66
    67      /**
    68       * Transfers the content of this file region to the specified channel.
    69       *
    70       * @param target    the destination of the transfer
    71       * @param position  the relative offset of the file where the transfer
    72       *                  begins from.  For example, <tt>0</tt> will make the
    73       *                  transfer start from {@link #getPosition()}th byte and
    74       *                  <tt>{@link #getCount()} - 1</tt> will make the last
    75       *                  byte of the region transferred.
    76       */
    77      long transferTo(WritableByteChannel target, long position) throws IOException;
    78  }