| /* |
| * Copyright (c) 2000, 2008, 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.nio.channels.SelectionKey; |
| import java.nio.channels.Selector; |
| import java.util.HashSet; |
| import java.util.Set; |
| import sun.nio.ch.Interruptible; |
| import java.util.concurrent.atomic.AtomicBoolean; |
| |
| |
| /** |
| * Base implementation class for selectors. |
| * |
| * <p> This class encapsulates the low-level machinery required to implement |
| * the interruption of selection operations. A concrete selector 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: <a name="be"> |
| * |
| * <blockquote><pre> |
| * try { |
| * begin(); |
| * // Perform blocking I/O operation here |
| * ... |
| * } finally { |
| * end(); |
| * }</pre></blockquote> |
| * |
| * <p> This class also defines methods for maintaining a selector's |
| * cancelled-key set and for removing a key from its channel's key set, and |
| * declares the abstract {@link #register register} method that is invoked by a |
| * selectable channel's {@link AbstractSelectableChannel#register register} |
| * method in order to perform the actual work of registering a channel. </p> |
| * |
| * |
| * @author Mark Reinhold |
| * @author JSR-51 Expert Group |
| * @since 1.4 |
| */ |
| |
| public abstract class AbstractSelector |
| extends Selector |
| { |
| |
| private AtomicBoolean selectorOpen = new AtomicBoolean(true); |
| |
| // The provider that created this selector |
| private final SelectorProvider provider; |
| |
| /** |
| * Initializes a new instance of this class. </p> |
| */ |
| protected AbstractSelector(SelectorProvider provider) { |
| this.provider = provider; |
| } |
| |
| private final Set<SelectionKey> cancelledKeys = new HashSet<SelectionKey>(); |
| |
| void cancel(SelectionKey k) { // package-private |
| synchronized (cancelledKeys) { |
| cancelledKeys.add(k); |
| } |
| } |
| |
| /** |
| * Closes this selector. |
| * |
| * <p> If the selector has already been closed then this method returns |
| * immediately. Otherwise it marks the selector as closed and then invokes |
| * the {@link #implCloseSelector implCloseSelector} method in order to |
| * complete the close operation. </p> |
| * |
| * @throws IOException |
| * If an I/O error occurs |
| */ |
| public final void close() throws IOException { |
| boolean open = selectorOpen.getAndSet(false); |
| if (!open) |
| return; |
| implCloseSelector(); |
| } |
| |
| /** |
| * Closes this selector. |
| * |
| * <p> This method is invoked by the {@link #close close} method in order |
| * to perform the actual work of closing the selector. This method is only |
| * invoked if the selector 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 a selection operation upon this selector to return |
| * immediately as if by invoking the {@link |
| * java.nio.channels.Selector#wakeup wakeup} method. </p> |
| * |
| * @throws IOException |
| * If an I/O error occurs while closing the selector |
| */ |
| protected abstract void implCloseSelector() throws IOException; |
| |
| public final boolean isOpen() { |
| return selectorOpen.get(); |
| } |
| |
| /** |
| * Returns the provider that created this channel. |
| * |
| * @return The provider that created this channel |
| */ |
| public final SelectorProvider provider() { |
| return provider; |
| } |
| |
| /** |
| * Retrieves this selector's cancelled-key set. |
| * |
| * <p> This set should only be used while synchronized upon it. </p> |
| * |
| * @return The cancelled-key set |
| */ |
| protected final Set<SelectionKey> cancelledKeys() { |
| return cancelledKeys; |
| } |
| |
| /** |
| * Registers the given channel with this selector. |
| * |
| * <p> This method is invoked by a channel's {@link |
| * AbstractSelectableChannel#register register} method in order to perform |
| * the actual work of registering the channel with this selector. </p> |
| * |
| * @param ch |
| * The channel to be registered |
| * |
| * @param ops |
| * The initial interest set, which must be valid |
| * |
| * @param att |
| * The initial attachment for the resulting key |
| * |
| * @return A new key representing the registration of the given channel |
| * with this selector |
| */ |
| protected abstract SelectionKey register(AbstractSelectableChannel ch, |
| int ops, Object att); |
| |
| /** |
| * Removes the given key from its channel's key set. |
| * |
| * <p> This method must be invoked by the selector for each channel that it |
| * deregisters. </p> |
| * |
| * @param key |
| * The selection key to be removed |
| */ |
| protected final void deregister(AbstractSelectionKey key) { |
| ((AbstractSelectableChannel)key.channel()).removeKey(key); |
| } |
| |
| |
| // -- Interruption machinery -- |
| |
| private Interruptible interruptor = null; |
| |
| /** |
| * 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 interruption for |
| * this selector. |
| * |
| * <p> Invoking this method arranges for the selector's {@link |
| * Selector#wakeup wakeup} method to be invoked if a thread's {@link |
| * Thread#interrupt interrupt} method is invoked while the thread is |
| * blocked in an I/O operation upon the selector. </p> |
| */ |
| protected final void begin() { |
| if (interruptor == null) { |
| interruptor = new Interruptible() { |
| public void interrupt() { |
| AbstractSelector.this.wakeup(); |
| }}; |
| } |
| AbstractInterruptibleChannel.blockedOn(interruptor); |
| if (Thread.currentThread().isInterrupted()) |
| interruptor.interrupt(); |
| } |
| |
| /** |
| * 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 interruption for |
| * this selector. </p> |
| */ |
| protected final void end() { |
| AbstractInterruptibleChannel.blockedOn(null); |
| } |
| |
| } |
