| /* |
| * Copyright (C) 2014 The Android Open Source Project |
| * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| /* |
| */ |
| |
| package java.nio.channels.spi; |
| |
| import java.io.IOException; |
| import java.lang.reflect.Method; |
| import java.lang.reflect.InvocationTargetException; |
| import java.nio.channels.*; |
| import java.security.AccessController; |
| import java.security.PrivilegedAction; |
| import sun.nio.ch.Interruptible; |
| |
| |
| /** |
| * Base implementation class for interruptible channels. |
| * |
| * <p> This class encapsulates the low-level machinery required to implement |
| * the asynchronous closing and interruption of channels. A concrete channel |
| * class must invoke the {@link #begin begin} and {@link #end end} methods |
| * before and after, respectively, invoking an I/O operation that might block |
| * indefinitely. In order to ensure that the {@link #end end} method is always |
| * invoked, these methods should be used within a |
| * <tt>try</tt> ... <tt>finally</tt> block: |
| * |
| * <blockquote><pre> |
| * boolean completed = false; |
| * try { |
| * begin(); |
| * completed = ...; // Perform blocking I/O operation |
| * return ...; // Return result |
| * } finally { |
| * end(completed); |
| * }</pre></blockquote> |
| * |
| * <p> The <tt>completed</tt> argument to the {@link #end end} method tells |
| * whether or not the I/O operation actually completed, that is, whether it had |
| * any effect that would be visible to the invoker. In the case of an |
| * operation that reads bytes, for example, this argument should be |
| * <tt>true</tt> if, and only if, some bytes were actually transferred into the |
| * invoker's target buffer. |
| * |
| * <p> A concrete channel class must also implement the {@link |
| * #implCloseChannel implCloseChannel} method in such a way that if it is |
| * invoked while another thread is blocked in a native I/O operation upon the |
| * channel then that operation will immediately return, either by throwing an |
| * exception or by returning normally. If a thread is interrupted or the |
| * channel upon which it is blocked is asynchronously closed then the channel's |
| * {@link #end end} method will throw the appropriate exception. |
| * |
| * <p> This class performs the synchronization required to implement the {@link |
| * java.nio.channels.Channel} specification. Implementations of the {@link |
| * #implCloseChannel implCloseChannel} method need not synchronize against |
| * other threads that might be attempting to close the channel. </p> |
| * |
| * |
| * @author Mark Reinhold |
| * @author JSR-51 Expert Group |
| * @since 1.4 |
| */ |
| |
| public abstract class AbstractInterruptibleChannel |
| implements Channel, InterruptibleChannel |
| { |
| |
| private final Object closeLock = new Object(); |
| private volatile boolean open = true; |
| |
| /** |
| * Initializes a new instance of this class. |
| */ |
| protected AbstractInterruptibleChannel() { } |
| |
| /** |
| * Closes this channel. |
| * |
| * <p> If the channel has already been closed then this method returns |
| * immediately. Otherwise it marks the channel as closed and then invokes |
| * the {@link #implCloseChannel implCloseChannel} method in order to |
| * complete the close operation. </p> |
| * |
| * @throws IOException |
| * If an I/O error occurs |
| */ |
| public final void close() throws IOException { |
| synchronized (closeLock) { |
| if (!open) |
| return; |
| open = false; |
| implCloseChannel(); |
| } |
| } |
| |
| /** |
| * Closes this channel. |
| * |
| * <p> This method is invoked by the {@link #close close} method in order |
| * to perform the actual work of closing the channel. This method is only |
| * invoked if the channel has not yet been closed, and it is never invoked |
| * more than once. |
| * |
| * <p> An implementation of this method must arrange for any other thread |
| * that is blocked in an I/O operation upon this channel to return |
| * immediately, either by throwing an exception or by returning normally. |
| * </p> |
| * |
| * @throws IOException |
| * If an I/O error occurs while closing the channel |
| */ |
| protected abstract void implCloseChannel() throws IOException; |
| |
| public final boolean isOpen() { |
| return open; |
| } |
| |
| |
| // -- Interruption machinery -- |
| |
| private Interruptible interruptor; |
| private volatile Thread interrupted; |
| |
| /** |
| * Marks the beginning of an I/O operation that might block indefinitely. |
| * |
| * <p> This method should be invoked in tandem with the {@link #end end} |
| * method, using a <tt>try</tt> ... <tt>finally</tt> block as |
| * shown <a href="#be">above</a>, in order to implement asynchronous |
| * closing and interruption for this channel. </p> |
| */ |
| protected final void begin() { |
| if (interruptor == null) { |
| interruptor = new Interruptible() { |
| public void interrupt(Thread target) { |
| synchronized (closeLock) { |
| if (!open) |
| return; |
| open = false; |
| interrupted = target; |
| try { |
| AbstractInterruptibleChannel.this.implCloseChannel(); |
| } catch (IOException x) { } |
| } |
| }}; |
| } |
| blockedOn(interruptor); |
| Thread me = Thread.currentThread(); |
| if (me.isInterrupted()) |
| interruptor.interrupt(me); |
| } |
| |
| /** |
| * Marks the end of an I/O operation that might block indefinitely. |
| * |
| * <p> This method should be invoked in tandem with the {@link #begin |
| * begin} method, using a <tt>try</tt> ... <tt>finally</tt> block |
| * as shown <a href="#be">above</a>, in order to implement asynchronous |
| * closing and interruption for this channel. </p> |
| * |
| * @param completed |
| * <tt>true</tt> if, and only if, the I/O operation completed |
| * successfully, that is, had some effect that would be visible to |
| * the operation's invoker |
| * |
| * @throws AsynchronousCloseException |
| * If the channel was asynchronously closed |
| * |
| * @throws ClosedByInterruptException |
| * If the thread blocked in the I/O operation was interrupted |
| */ |
| protected final void end(boolean completed) |
| throws AsynchronousCloseException |
| { |
| blockedOn(null); |
| Thread interrupted = this.interrupted; |
| if (interrupted != null && interrupted == Thread.currentThread()) { |
| interrupted = null; |
| throw new ClosedByInterruptException(); |
| } |
| if (!completed && !open) |
| throw new AsynchronousCloseException(); |
| } |
| |
| |
| // -- sun.misc.SharedSecrets -- |
| static void blockedOn(Interruptible intr) { // package-private |
| // Android-changed: Call Thread.currentThread().blockedOn() directly. |
| Thread.currentThread().blockedOn(intr); |
| } |
| } |
