001/* AbstractSelector.java --
002   Copyright (C) 2002, 2003, 2004, 2005  Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038package java.nio.channels.spi;
039
040import java.io.IOException;
041import java.nio.channels.ClosedSelectorException;
042import java.nio.channels.SelectionKey;
043import java.nio.channels.Selector;
044import java.util.HashSet;
045import java.util.Set;
046
047
048public abstract class AbstractSelector extends Selector
049{
050  private boolean closed;
051  private SelectorProvider provider;
052  private HashSet<SelectionKey> cancelledKeys;
053
054  /**
055   * Initializes the slector.
056   *
057   * @param provider the provider that created this selector
058   */
059  protected AbstractSelector(SelectorProvider provider)
060  {
061    this.provider = provider;
062    this.cancelledKeys = new HashSet<SelectionKey>();
063  }
064
065  /**
066   * Closes the channel.
067   *
068   * @exception IOException If an error occurs
069   */
070  public final synchronized void close() throws IOException
071  {
072    if (closed)
073      return;
074
075    implCloseSelector();
076    closed = true;
077  }
078
079  /**
080   * Tells whether this channel is open or not.
081   *
082   * @return true if channel is open, false otherwise.
083   */
084  public final boolean isOpen()
085  {
086    return ! closed;
087  }
088
089  /**
090   * Marks the beginning of an I/O operation that might block indefinitely.
091   */
092  protected final void begin()
093  {
094  }
095
096  /**
097   * Marks the end of an I/O operation that might block indefinitely.
098   */
099  protected final void end()
100  {
101  }
102
103  /**
104   * Returns the provider for this selector object.
105   *
106   * @return the SelectorProvider object that created this seletor
107   */
108  public final SelectorProvider provider()
109  {
110    return provider;
111  }
112
113  /**
114   * Returns the cancelled keys set.
115   *
116   * @return the cancelled keys set
117   */
118  protected final Set<SelectionKey> cancelledKeys()
119  {
120    if (! isOpen())
121      throw new ClosedSelectorException();
122
123    return cancelledKeys;
124  }
125
126  /**
127   * Cancels a selection key.
128   */
129
130  // This method is only called by AbstractSelectionKey.cancel().
131  final void cancelKey(AbstractSelectionKey key)
132  {
133    synchronized (cancelledKeys)
134      {
135        cancelledKeys.add(key);
136      }
137  }
138
139  /**
140   * Closes the channel.
141   *
142   * @exception IOException if an error occurs
143   */
144  protected abstract void implCloseSelector() throws IOException;
145
146  /**
147   * Registers a channel for the selection process.
148   *
149   * @param ch the channel register
150   * @param ops the interested operations
151   * @param att an attachement to the selection key
152   *
153   * @return the registered selection key
154   */
155  protected abstract SelectionKey register(AbstractSelectableChannel ch,
156                                           int ops, Object att);
157
158  /**
159   * Deregisters the given selection key.
160   *
161   * @param key the key to deregister
162   */
163  protected final void deregister(AbstractSelectionKey key)
164  {
165    ((AbstractSelectableChannel) key.channel()).removeSelectionKey(key);
166  }
167}