2362N/A * Copyright (c) 2007, 2009, Oracle and/or its affiliates. All rights reserved. 893N/A * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 893N/A * This code is free software; you can redistribute it and/or modify it 893N/A * under the terms of the GNU General Public License version 2 only, as 2362N/A * published by the Free Software Foundation. Oracle designates this 893N/A * particular file as subject to the "Classpath" exception as provided 2362N/A * by Oracle in the LICENSE file that accompanied this code. 893N/A * This code is distributed in the hope that it will be useful, but WITHOUT 893N/A * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 893N/A * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 893N/A * version 2 for more details (a copy is included in the LICENSE file that 893N/A * accompanied this code). 893N/A * You should have received a copy of the GNU General Public License version 893N/A * 2 along with this work; if not, write to the Free Software Foundation, 893N/A * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 2362N/A * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 2362N/A * or visit www.oracle.com if you need additional information or have any 893N/A * A channel that supports asynchronous I/O operations. Asynchronous I/O 893N/A * operations will usually take one of two forms: 893N/A * <li><pre>{@link Future}<V> <em>operation</em>(<em>...</em>)</pre></li> 1580N/A * <li><pre>void <em>operation</em>(<em>...</em> A attachment, {@link 1580N/A * CompletionHandler}<V,? super A> handler)</pre></li> 893N/A * where <i>operation</i> is the name of the I/O operation (read or write for 893N/A * example), <i>V</i> is the result type of the I/O operation, and <i>A</i> is 893N/A * the type of an object attached to the I/O operation to provide context when 893N/A * consuming the result. The attachment is important for cases where a 893N/A * <em>state-less</em> {@code CompletionHandler} is used to consume the result 893N/A * of many I/O operations. 893N/A * <p> In the first form, the methods defined by the {@link Future Future} 893N/A * interface may be used to check if the operation has completed, wait for its 893N/A * completion, and to retrieve the result. In the second form, a {@link 893N/A * CompletionHandler} is invoked to consume the result of the I/O operation when 893N/A * <p> A channel that implements this interface is <em>asynchronously 893N/A * closeable</em>: If an I/O operation is outstanding on the channel and the 893N/A * channel's {@link #close close} method is invoked, then the I/O operation 893N/A * fails with the exception {@link AsynchronousCloseException}. 893N/A * <p> Asynchronous channels are safe for use by multiple concurrent threads. 893N/A * Some channel implementations may support concurrent reading and writing, but 893N/A * may not allow more than one read and one write operation to be outstanding at 893N/A * <h4>Cancellation</h4> 893N/A * <p> The {@code Future} interface defines the {@link Future#cancel cancel} 1580N/A * method to cancel execution. This causes all threads waiting on the result of 1580N/A * the I/O operation to throw {@link java.util.concurrent.CancellationException}. 1580N/A * Whether the underlying I/O operation can be cancelled is highly implementation 1580N/A * specific and therefore not specified. Where cancellation leaves the channel, 1580N/A * or the entity to which it is connected, in an inconsistent state, then the 1580N/A * channel is put into an implementation specific <em>error state</em> that 1580N/A * prevents further attempts to initiate I/O operations that are <i>similar</i> 1580N/A * to the operation that was cancelled. For example, if a read operation is 1580N/A * cancelled but the implementation cannot guarantee that bytes have not been 1580N/A * read from the channel then it puts the channel into an error state; further 1580N/A * attempts to initiate a {@code read} operation cause an unspecified runtime 1580N/A * exception to be thrown. Similarly, if a write operation is cancelled but the 1580N/A * implementation cannot guarantee that bytes have not been written to the 1580N/A * channel then subsequent attempts to initiate a {@code write} will fail with 1580N/A * an unspecified runtime exception. 1580N/A * <p> Where the {@link Future#cancel cancel} method is invoked with the {@code 1580N/A * mayInterruptIfRunning} parameter set to {@code true} then the I/O operation 1580N/A * may be interrupted by closing the channel. In that case all threads waiting 1580N/A * on the result of the I/O operation throw {@code CancellationException} and 1580N/A * any other I/O operations outstanding on the channel complete with the 1580N/A * exception {@link AsynchronousCloseException}. 893N/A * <p> Where the {@code cancel} method is invoked to cancel read or write 1580N/A * operations then it is recommended that all buffers used in the I/O operations 1580N/A * be discarded or care taken to ensure that the buffers are not accessed while 1580N/A * the channel remains open. 893N/A * <p> Any outstanding asynchronous operations upon this channel will 893N/A * complete with the exception {@link AsynchronousCloseException}. After a 1580N/A * channel is closed, further attempts to initiate asynchronous I/O 893N/A * operations complete immediately with cause {@link ClosedChannelException}. 893N/A * <p> This method otherwise behaves exactly as specified by the {@link 893N/A * If an I/O error occurs