| /* |
| * 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; |
| |
| import java.io.IOException; |
| import java.nio.channels.spi.AbstractInterruptibleChannel; |
| import java.nio.channels.spi.SelectorProvider; |
| |
| |
| /** |
| * A channel that can be multiplexed via a {@link Selector}. |
| * |
| * <p> In order to be used with a selector, an instance of this class must |
| * first be <i>registered</i> via the {@link #register(Selector,int,Object) |
| * register} method. This method returns a new {@link SelectionKey} object |
| * that represents the channel's registration with the selector. |
| * |
| * <p> Once registered with a selector, a channel remains registered until it |
| * is <i>deregistered</i>. This involves deallocating whatever resources were |
| * allocated to the channel by the selector. |
| * |
| * <p> A channel cannot be deregistered directly; instead, the key representing |
| * its registration must be <i>cancelled</i>. Cancelling a key requests that |
| * the channel be deregistered during the selector's next selection operation. |
| * A key may be cancelled explicitly by invoking its {@link |
| * SelectionKey#cancel() cancel} method. All of a channel's keys are cancelled |
| * implicitly when the channel is closed, whether by invoking its {@link |
| * Channel#close close} method or by interrupting a thread blocked in an I/O |
| * operation upon the channel. |
| * |
| * <p> If the selector itself is closed then the channel will be deregistered, |
| * and the key representing its registration will be invalidated, without |
| * further delay. |
| * |
| * <p> A channel may be registered at most once with any particular selector. |
| * |
| * <p> Whether or not a channel is registered with one or more selectors may be |
| * determined by invoking the {@link #isRegistered isRegistered} method. |
| * |
| * <p> Selectable channels are safe for use by multiple concurrent |
| * threads. </p> |
| * |
| * |
| * <a name="bm"></a> |
| * <h2>Blocking mode</h2> |
| * |
| * A selectable channel is either in <i>blocking</i> mode or in |
| * <i>non-blocking</i> mode. In blocking mode, every I/O operation invoked |
| * upon the channel will block until it completes. In non-blocking mode an I/O |
| * operation will never block and may transfer fewer bytes than were requested |
| * or possibly no bytes at all. The blocking mode of a selectable channel may |
| * be determined by invoking its {@link #isBlocking isBlocking} method. |
| * |
| * <p> Newly-created selectable channels are always in blocking mode. |
| * Non-blocking mode is most useful in conjunction with selector-based |
| * multiplexing. A channel must be placed into non-blocking mode before being |
| * registered with a selector, and may not be returned to blocking mode until |
| * it has been deregistered. |
| * |
| * |
| * @author Mark Reinhold |
| * @author JSR-51 Expert Group |
| * @since 1.4 |
| * |
| * @see SelectionKey |
| * @see Selector |
| */ |
| |
| public abstract class SelectableChannel |
| extends AbstractInterruptibleChannel |
| implements Channel |
| { |
| |
| /** |
| * Initializes a new instance of this class. |
| */ |
| protected SelectableChannel() { } |
| |
| /** |
| * Returns the provider that created this channel. |
| * |
| * @return The provider that created this channel |
| */ |
| public abstract SelectorProvider provider(); |
| |
| /** |
| * Returns an <a href="SelectionKey.html#opsets">operation set</a> |
| * identifying this channel's supported operations. The bits that are set |
| * in this integer value denote exactly the operations that are valid for |
| * this channel. This method always returns the same value for a given |
| * concrete channel class. |
| * |
| * @return The valid-operation set |
| */ |
| public abstract int validOps(); |
| |
| // Internal state: |
| // keySet, may be empty but is never null, typ. a tiny array |
| // boolean isRegistered, protected by key set |
| // regLock, lock object to prevent duplicate registrations |
| // boolean isBlocking, protected by regLock |
| |
| /** |
| * Tells whether or not this channel is currently registered with any |
| * selectors. A newly-created channel is not registered. |
| * |
| * <p> Due to the inherent delay between key cancellation and channel |
| * deregistration, a channel may remain registered for some time after all |
| * of its keys have been cancelled. A channel may also remain registered |
| * for some time after it is closed. </p> |
| * |
| * @return <tt>true</tt> if, and only if, this channel is registered |
| */ |
| public abstract boolean isRegistered(); |
| // |
| // sync(keySet) { return isRegistered; } |
| |
| /** |
| * Retrieves the key representing the channel's registration with the given |
| * selector. |
| * |
| * @param sel |
| * The selector |
| * |
| * @return The key returned when this channel was last registered with the |
| * given selector, or <tt>null</tt> if this channel is not |
| * currently registered with that selector |
| */ |
| public abstract SelectionKey keyFor(Selector sel); |
| // |
| // sync(keySet) { return findKey(sel); } |
| |
| /** |
| * Registers this channel with the given selector, returning a selection |
| * key. |
| * |
| * <p> If this channel is currently registered with the given selector then |
| * the selection key representing that registration is returned. The key's |
| * interest set will have been changed to <tt>ops</tt>, as if by invoking |
| * the {@link SelectionKey#interestOps(int) interestOps(int)} method. If |
| * the <tt>att</tt> argument is not <tt>null</tt> then the key's attachment |
| * will have been set to that value. A {@link CancelledKeyException} will |
| * be thrown if the key has already been cancelled. |
| * |
| * <p> Otherwise this channel has not yet been registered with the given |
| * selector, so it is registered and the resulting new key is returned. |
| * The key's initial interest set will be <tt>ops</tt> and its attachment |
| * will be <tt>att</tt>. |
| * |
| * <p> This method may be invoked at any time. If this method is invoked |
| * while another invocation of this method or of the {@link |
| * #configureBlocking(boolean) configureBlocking} method is in progress |
| * then it will first block until the other operation is complete. This |
| * method will then synchronize on the selector's key set and therefore may |
| * block if invoked concurrently with another registration or selection |
| * operation involving the same selector. </p> |
| * |
| * <p> If this channel is closed while this operation is in progress then |
| * the key returned by this method will have been cancelled and will |
| * therefore be invalid. </p> |
| * |
| * @param sel |
| * The selector with which this channel is to be registered |
| * |
| * @param ops |
| * The interest set for the resulting key |
| * |
| * @param att |
| * The attachment for the resulting key; may be <tt>null</tt> |
| * |
| * @throws ClosedChannelException |
| * If this channel is closed |
| * |
| * @throws ClosedSelectorException |
| * If the selector is closed |
| * |
| * @throws IllegalBlockingModeException |
| * If this channel is in blocking mode |
| * |
| * @throws IllegalSelectorException |
| * If this channel was not created by the same provider |
| * as the given selector |
| * |
| * @throws CancelledKeyException |
| * If this channel is currently registered with the given selector |
| * but the corresponding key has already been cancelled |
| * |
| * @throws IllegalArgumentException |
| * If a bit in the <tt>ops</tt> set does not correspond to an |
| * operation that is supported by this channel, that is, if |
| * {@code set & ~validOps() != 0} |
| * |
| * @return A key representing the registration of this channel with |
| * the given selector |
| */ |
| public abstract SelectionKey register(Selector sel, int ops, Object att) |
| throws ClosedChannelException; |
| // |
| // sync(regLock) { |
| // sync(keySet) { look for selector } |
| // if (channel found) { set interest ops -- may block in selector; |
| // return key; } |
| // create new key -- may block somewhere in selector; |
| // sync(keySet) { add key; } |
| // attach(attachment); |
| // return key; |
| // } |
| |
| /** |
| * Registers this channel with the given selector, returning a selection |
| * key. |
| * |
| * <p> An invocation of this convenience method of the form |
| * |
| * <blockquote><tt>sc.register(sel, ops)</tt></blockquote> |
| * |
| * behaves in exactly the same way as the invocation |
| * |
| * <blockquote><tt>sc.{@link |
| * #register(java.nio.channels.Selector,int,java.lang.Object) |
| * register}(sel, ops, null)</tt></blockquote> |
| * |
| * @param sel |
| * The selector with which this channel is to be registered |
| * |
| * @param ops |
| * The interest set for the resulting key |
| * |
| * @throws ClosedChannelException |
| * If this channel is closed |
| * |
| * @throws ClosedSelectorException |
| * If the selector is closed |
| * |
| * @throws IllegalBlockingModeException |
| * If this channel is in blocking mode |
| * |
| * @throws IllegalSelectorException |
| * If this channel was not created by the same provider |
| * as the given selector |
| * |
| * @throws CancelledKeyException |
| * If this channel is currently registered with the given selector |
| * but the corresponding key has already been cancelled |
| * |
| * @throws IllegalArgumentException |
| * If a bit in <tt>ops</tt> does not correspond to an operation |
| * that is supported by this channel, that is, if {@code set & |
| * ~validOps() != 0} |
| * |
| * @return A key representing the registration of this channel with |
| * the given selector |
| */ |
| public final SelectionKey register(Selector sel, int ops) |
| throws ClosedChannelException |
| { |
| return register(sel, ops, null); |
| } |
| |
| /** |
| * Adjusts this channel's blocking mode. |
| * |
| * <p> If this channel is registered with one or more selectors then an |
| * attempt to place it into blocking mode will cause an {@link |
| * IllegalBlockingModeException} to be thrown. |
| * |
| * <p> This method may be invoked at any time. The new blocking mode will |
| * only affect I/O operations that are initiated after this method returns. |
| * For some implementations this may require blocking until all pending I/O |
| * operations are complete. |
| * |
| * <p> If this method is invoked while another invocation of this method or |
| * of the {@link #register(Selector, int) register} method is in progress |
| * then it will first block until the other operation is complete. </p> |
| * |
| * @param block If <tt>true</tt> then this channel will be placed in |
| * blocking mode; if <tt>false</tt> then it will be placed |
| * non-blocking mode |
| * |
| * @return This selectable channel |
| * |
| * @throws ClosedChannelException |
| * If this channel is closed |
| * |
| * @throws IllegalBlockingModeException |
| * If <tt>block</tt> is <tt>true</tt> and this channel is |
| * registered with one or more selectors |
| * |
| * @throws IOException |
| * If an I/O error occurs |
| */ |
| public abstract SelectableChannel configureBlocking(boolean block) |
| throws IOException; |
| // |
| // sync(regLock) { |
| // sync(keySet) { throw IBME if block && isRegistered; } |
| // change mode; |
| // } |
| |
| /** |
| * Tells whether or not every I/O operation on this channel will block |
| * until it completes. A newly-created channel is always in blocking mode. |
| * |
| * <p> If this channel is closed then the value returned by this method is |
| * not specified. </p> |
| * |
| * @return <tt>true</tt> if, and only if, this channel is in blocking mode |
| */ |
| public abstract boolean isBlocking(); |
| |
| /** |
| * Retrieves the object upon which the {@link #configureBlocking |
| * configureBlocking} and {@link #register register} methods synchronize. |
| * This is often useful in the implementation of adaptors that require a |
| * specific blocking mode to be maintained for a short period of time. |
| * |
| * @return The blocking-mode lock object |
| */ |
| public abstract Object blockingLock(); |
| |
| } |
