93 lines
3.8 KiB
Java
93 lines
3.8 KiB
Java
/*
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* Copyright 2010 Red Hat, Inc.
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*
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* Red Hat licenses this file to you under the Apache License, version 2.0
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* (the "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*/
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package io.netty.channel;
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import java.io.IOException;
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import java.nio.channels.FileChannel;
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import java.nio.channels.WritableByteChannel;
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import io.netty.util.ExternalResourceReleasable;
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/**
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* A region of a file that is sent via a {@link Channel} which supports
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* <a href="http://en.wikipedia.org/wiki/Zero-copy">zero-copy file transfer</a>.
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*
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* <h3>Upgrade your JDK / JRE</h3>
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*
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* {@link FileChannel#transferTo(long, long, WritableByteChannel)} has at least
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* four known bugs in the old versions of Sun JDK and perhaps its derived ones.
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* Please upgrade your JDK to 1.6.0_18 or later version if you are going to use
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* zero-copy file transfer.
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* <ul>
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* <li><a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=5103988">5103988</a>
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* - FileChannel.transferTo() should return -1 for EAGAIN instead throws IOException</li>
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* <li><a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6253145">6253145</a>
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* - FileChannel.transferTo() on Linux fails when going beyond 2GB boundary</li>
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* <li><a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6427312">6427312</a>
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* - FileChannel.transferTo() throws IOException "system call interrupted"</li>
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* <li><a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6524172">6470086</a>
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* - FileChannel.transferTo(2147483647, 1, channel) causes "Value too large" exception</li>
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* </ul>
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*
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* <h3>Check your operating system and JDK / JRE</h3>
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*
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* If your operating system (or JDK / JRE) does not support zero-copy file
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* transfer, sending a file with {@link FileRegion} might fail or yield worse
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* performance. For example, sending a large file doesn't work well in Windows.
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*
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* <h3>Not all transports support it</h3>
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*
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* Currently, the NIO transport is the only transport that supports {@link FileRegion}.
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* Attempting to write a {@link FileRegion} to non-NIO {@link Channel} will trigger
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* a {@link ClassCastException} or a similar exception.
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*
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* @author <a href="http://netty.io/">The Netty Project</a>
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* @author <a href="http://gleamynode.net/">Trustin Lee</a>
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*/
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public interface FileRegion extends ExternalResourceReleasable {
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// FIXME Make sure all transports support writing a FileRegion
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// Even if zero copy cannot be achieved, all transports should emulate it.
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/**
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* Returns the offset in the file where the transfer began.
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*/
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long getPosition();
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/**
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* Returns the number of bytes to transfer.
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*/
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long getCount();
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/**
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* Returns <code>true</code> if {@link #releaseExternalResources()} has to
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* be called after the transfer of this {@link FileRegion} is complete.
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*/
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boolean releaseAfterTransfer();
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/**
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* Transfers the content of this file region to the specified channel.
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*
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* @param target the destination of the transfer
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* @param position the relative offset of the file where the transfer
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* begins from. For example, <tt>0</tt> will make the
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* transfer start from {@link #getPosition()}th byte and
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* <tt>{@link #getCount()} - 1</tt> will make the last
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* byte of the region transferred.
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*/
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long transferTo(WritableByteChannel target, long position) throws IOException;
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}
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