Initial revision

From-SVN: r102074

libjava/classpath/java/nio/channels/spi/AbstractSelectableChannel.java

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+/* AbstractSelectableChannel.java
+   Copyright (C) 2002, 2003, 2004 Free Software Foundation, Inc.
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+GNU Classpath 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 for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library.  Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module.  An independent module is a module which is not derived from
+or based on this library.  If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so.  If you do not wish to do so, delete this
+exception statement from your version. */
+
+
+package java.nio.channels.spi;
+
+import java.io.IOException;
+import java.nio.channels.ClosedChannelException;
+import java.nio.channels.SelectableChannel;
+import java.nio.channels.SelectionKey;
+import java.nio.channels.Selector;
+import java.util.LinkedList;
+import java.util.ListIterator;
+
+public abstract class AbstractSelectableChannel extends SelectableChannel
+{
+  private boolean blocking = true;
+  private Object LOCK = new Object();
+  private SelectorProvider provider;
+  private LinkedList keys = new LinkedList();
+
+  /**
+   * Initializes the channel
+   *
+   * @param provider the provider that created this channel
+   */
+  protected AbstractSelectableChannel(SelectorProvider provider)
+  {
+    this.provider = provider;
+  }
+
+  /**
+   * Retrieves the object upon which the configureBlocking and register
+   * methods synchronize.
+   *
+   * @return the blocking lock
+   */
+  public final Object blockingLock()
+  {
+    return LOCK;
+  }
+
+  /**
+   * Adjusts this channel's blocking mode.
+   *
+   * @param blocking true if blocking should be enabled, false otherwise
+   *
+   * @return this channel
+   *
+   * @exception IOException If an error occurs
+   */
+  public final SelectableChannel configureBlocking(boolean blocking)
+    throws IOException
+  {
+    synchronized (blockingLock())
+      {
+	if (this.blocking != blocking)
+	  {
+	    implConfigureBlocking(blocking);
+	    this.blocking = blocking;
+	  }
+      }
+
+    return this;
+  }
+
+  /**
+   * Closes this channel.
+   *
+   * @exception IOException If an error occurs
+   */
+  protected final void implCloseChannel() throws IOException
+  {
+    implCloseSelectableChannel();
+  }
+
+  /**
+   * Closes this selectable channel.
+   *
+   * @exception IOException If an error occurs
+   */
+  protected abstract void implCloseSelectableChannel()
+    throws IOException;
+
+  /**
+   * Adjusts this channel's blocking mode.
+   *
+   * @param blocking true if blocking should be enabled, false otherwise
+   *
+   * @exception IOException If an error occurs
+   */
+  protected abstract void implConfigureBlocking(boolean blocking)
+    throws IOException;
+
+  /**
+   * Tells whether or not every I/O operation on this channel will block
+   * until it completes.
+   *
+   * @return true of this channel is blocking, false otherwise
+   */
+  public final boolean isBlocking()
+  {
+    return blocking;
+  }
+
+  /**
+   * Tells whether or not this channel is currently registered with
+   * any selectors.
+   *
+   * @return true if this channel is registered, false otherwise
+   */
+  public final boolean isRegistered()
+  {
+    return ! keys.isEmpty();
+  }
+
+  /**
+   * Retrieves the key representing the channel's registration with the
+   * given selector.
+   *
+   * @param selector the selector to get a selection key for
+   *
+   * @return the selection key this channel is registered with
+   */
+  public final SelectionKey keyFor(Selector selector)
+  {
+    if (! isOpen())
+      return null;
+
+    try
+      {
+	synchronized (blockingLock())
+	  {
+	    return locate(selector);
+	  }
+      }
+    catch (Exception e)
+      {
+	return null;
+      }
+  }
+
+  /**
+   * Returns the provider that created this channel.
+   *
+   * @return the selector provider that created this channel
+   */
+  public final SelectorProvider provider()
+  {
+    return provider;
+  }
+
+  private SelectionKey locate(Selector selector)
+  {
+    ListIterator it = keys.listIterator();
+
+    while (it.hasNext())
+      {
+	SelectionKey key = (SelectionKey) it.next();
+
+	if (key.selector() == selector)
+	  return key;
+      }
+
+    return null;
+  }
+
+  /**
+   * Registers this channel with the given selector, returning a selection key.
+   *
+   * @param selin the seletor to use
+   * @param ops the interested operations
+   * @param att an attachment for the returned selection key
+   *
+   * @return the registered selection key
+   * 
+   * @exception ClosedChannelException If the channel is already closed.
+   */
+  public final SelectionKey register(Selector selin, int ops, Object att)
+    throws ClosedChannelException
+  {
+    if (! isOpen())
+      throw new ClosedChannelException();
+
+    if ((ops & ~validOps()) != 0)
+      throw new IllegalArgumentException();
+    
+    SelectionKey key = null;
+    AbstractSelector selector = (AbstractSelector) selin;
+
+    synchronized (blockingLock())
+      {
+	key = locate(selector);
+
+	if (key != null && key.isValid())
+	  {
+	    if (att != null)
+	      key.attach(att);
+	  }
+	else
+	  {
+	    key = selector.register(this, ops, att);
+
+	    if (key != null)
+	      addSelectionKey(key);
+	  }
+      }
+
+    return key;
+  }
+
+  void addSelectionKey(SelectionKey key)
+  {
+    keys.add(key);
+  }
+
+  // This method gets called by AbstractSelector.deregister().
+  void removeSelectionKey(SelectionKey key)
+  {
+    keys.remove(key);
+  }
+}