/* * 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; 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"> * <h4>Blocking mode</h4> * * 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. </p> * * @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. </p> * * @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 * <tt>set & ~validOps() != 0</tt> * * @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 <tt>set & * ~validOps() != 0</tt> * * @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. * </p> * * @return The blocking-mode lock object */ public abstract Object blockingLock(); }
/*
* 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;
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">
* <h4>Blocking mode</h4>
*
* 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. </p>
*
* @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. </p>
*
* @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
* <tt>set & ~validOps() != 0</tt>
*
* @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 <tt>set &
* ~validOps() != 0</tt>
*
* @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.
* </p>
*
* @return The blocking-mode lock object
*/
public abstract Object blockingLock();
}