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

   1 /* AbstractSelectableChannel.java
   2    Copyright (C) 2002, 2003 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38 package java.nio.channels.spi;
  39
  40 import java.io.IOException;
  41 import java.nio.channels.ClosedChannelException;
  42 import java.nio.channels.SelectableChannel;
  43 import java.nio.channels.SelectionKey;
  44 import java.nio.channels.Selector;
  45 import java.util.LinkedList;
  46 import java.util.List;
  47 import java.util.ListIterator;
  48
  49 public abstract class AbstractSelectableChannel extends SelectableChannel
  50 {
  51   private int registered;
  52   private boolean blocking = true;
  53   private Object LOCK = new Object();
  54   private SelectorProvider provider;
  55   private LinkedList keys;
  56
  57   /**
  58    * Initializes the channel
  59    */
  60   protected AbstractSelectableChannel (SelectorProvider provider)
  61   {
  62     this.provider = provider;
  63     this.keys = new LinkedList();
  64   }
  65
  66   /**
  67    * Retrieves the object upon which the configureBlocking and register
  68    * methods synchronize.
  69    */
  70   public final Object blockingLock ()
  71   {
  72     return LOCK;
  73   }
  74
  75   /**
  76    * Adjusts this channel's blocking mode.
  77    */
  78   public final SelectableChannel configureBlocking (boolean blocking)
  79     throws IOException
  80   {
  81     synchronized (blockingLock())
  82       {
  83         implConfigureBlocking(blocking);
  84         this.blocking = blocking;
  85       }
  86
  87     return this;
  88   }
  89
  90   /**
  91    * Closes this channel.
  92    *
  93    * @exception IOException If an error occurs
  94    */
  95   protected final void implCloseChannel () throws IOException
  96   {
  97     implCloseSelectableChannel ();
  98   }
  99
 100   /**
 101    * Closes this selectable channel.
 102    */
 103   protected abstract void implCloseSelectableChannel () throws IOException;
 104
 105   /**
 106    * Adjusts this channel's blocking mode.
 107    */
 108   protected abstract void implConfigureBlocking (boolean block)
 109     throws IOException;
 110
 111   /**
 112    * Tells whether or not every I/O operation on this channel will block
 113    * until it completes.
 114    */
 115   public final boolean isBlocking()
 116   {
 117     return blocking;
 118   }
 119
 120   /**
 121    * Tells whether or not this channel is currently registered with
 122    * any selectors.
 123    */
 124   public final boolean isRegistered()
 125   {
 126     return !keys.isEmpty();
 127   }
 128
 129   /**
 130    * Retrieves the key representing the channel's registration with the
 131    * given selector.
 132    */
 133   public final SelectionKey keyFor(Selector selector)
 134   {
 135     try
 136       {
 137         return register (selector, 0, null);
 138       }
 139     catch (Exception e)
 140       {
 141         return null;
 142       }
 143   }
 144
 145   /**
 146    * Returns the provider that created this channel.
 147    */
 148   public final SelectorProvider provider ()
 149   {
 150     return provider;
 151   }
 152
 153   private SelectionKey locate (Selector selector)
 154   {
 155     if (keys == null)
 156       return null;
 157
 158     ListIterator it = keys.listIterator ();
 159
 160     while (it.hasNext ())
 161       {
 162         SelectionKey key = (SelectionKey) it.next();
 163
 164         if (key.selector() == selector)
 165           return key;
 166       }
 167
 168     return null;
 169   }
 170
 171   private void add (SelectionKey key)
 172   {
 173     keys.add (key);
 174   }
 175
 176   /**
 177    * Registers this channel with the given selector, returning a selection key.
 178    *
 179    * @exception ClosedChannelException If the channel is already closed.
 180    */
 181   public final SelectionKey register (Selector selin, int ops, Object att)
 182     throws ClosedChannelException
 183   {
 184     if (!isOpen ())
 185       throw new ClosedChannelException();
 186
 187     SelectionKey key = null;
 188     AbstractSelector selector = (AbstractSelector) selin;
 189
 190     synchronized (blockingLock())
 191       {
 192         key = locate (selector);
 193
 194         if (key != null)
 195           {
 196             key.attach (att);
 197           }
 198         else
 199           {
 200             key = selector.register (this, ops, att);
 201
 202             if (key != null)
 203               add (key);
 204           }
 205       }
 206
 207     return key;
 208   }
 209 }