001    /* AbstractSelector.java --
002       Copyright (C) 2002, 2003, 2004, 2005  Free Software Foundation, Inc.
003    
004    This file is part of GNU Classpath.
005    
006    GNU Classpath is free software; you can redistribute it and/or modify
007    it under the terms of the GNU General Public License as published by
008    the Free Software Foundation; either version 2, or (at your option)
009    any later version.
010    
011    GNU Classpath is distributed in the hope that it will be useful, but
012    WITHOUT ANY WARRANTY; without even the implied warranty of
013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014    General Public License for more details.
015    
016    You should have received a copy of the GNU General Public License
017    along with GNU Classpath; see the file COPYING.  If not, write to the
018    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019    02110-1301 USA.
020    
021    Linking this library statically or dynamically with other modules is
022    making a combined work based on this library.  Thus, the terms and
023    conditions of the GNU General Public License cover the whole
024    combination.
025    
026    As a special exception, the copyright holders of this library give you
027    permission to link this library with independent modules to produce an
028    executable, regardless of the license terms of these independent
029    modules, and to copy and distribute the resulting executable under
030    terms of your choice, provided that you also meet, for each linked
031    independent module, the terms and conditions of the license of that
032    module.  An independent module is a module which is not derived from
033    or based on this library.  If you modify this library, you may extend
034    this exception to your version of the library, but you are not
035    obligated to do so.  If you do not wish to do so, delete this
036    exception statement from your version. */
037    
038    package java.nio.channels.spi;
039    
040    import java.io.IOException;
041    import java.nio.channels.ClosedSelectorException;
042    import java.nio.channels.SelectionKey;
043    import java.nio.channels.Selector;
044    import java.util.HashSet;
045    import java.util.Set;
046    
047    
048    public 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    }