/*
* Copyright 2011 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 java.io.IOException;
import java.nio.channels.FileChannel;
import java.nio.channels.WritableByteChannel;
import org.jboss.netty.util.ExternalResourceReleasable;
/**
* A region of a file that is sent via a {@link Channel} which supports
* <a href="http://en.wikipedia.org/wiki/Zero-copy">zero-copy file transfer</a>.
*
* <h3>Upgrade your JDK / JRE</h3>
*
* {@link FileChannel#transferTo(long, long, WritableByteChannel)} has at least
* four known bugs in the old versions of Sun JDK and perhaps its derived ones.
* Please upgrade your JDK to 1.6.0_18 or later version if you are going to use
* zero-copy file transfer.
* <ul>
* <li><a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=5103988">5103988</a>
* - FileChannel.transferTo() should return -1 for EAGAIN instead throws IOException</li>
* <li><a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6253145">6253145</a>
* - FileChannel.transferTo() on Linux fails when going beyond 2GB boundary</li>
* <li><a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6427312">6427312</a>
* - FileChannel.transferTo() throws IOException "system call interrupted"</li>
* <li><a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6524172">6470086</a>
* - FileChannel.transferTo(2147483647, 1, channel) causes "Value too large" exception</li>
* </ul>
*
* <h3>Check your operating system and JDK / JRE</h3>
*
* If your operating system (or JDK / JRE) does not support zero-copy file
* transfer, sending a file with {@link FileRegion} might fail or yield worse
* performance. For example, sending a large file doesn't work well in Windows.
*
* <h3>Not all transports support it</h3>
*
* Currently, the NIO transport is the only transport that supports {@link FileRegion}.
* Attempting to write a {@link FileRegion} to non-NIO {@link Channel} will trigger
* a {@link ClassCastException} or a similar exception.
*/
public interface FileRegion extends ExternalResourceReleasable {
// FIXME Make sure all transports support writing a FileRegion
// Even if zero copy cannot be achieved, all transports should emulate it.
/**
* Returns the offset in the file where the transfer began.
*/
long getPosition();
/**
* Returns the number of bytes to transfer.
*/
long getCount();
/**
* Transfers the content of this file region to the specified channel.
*
* @param target the destination of the transfer
* @param position the relative offset of the file where the transfer
* begins from. For example, <tt>0</tt> will make the
* transfer start from {@link #getPosition()}th byte and
* <tt>{@link #getCount()} - 1</tt> will make the last
* byte of the region transferred.
*/
long transferTo(WritableByteChannel target, long position) throws IOException;
}