toolchain/gcc/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         if (this.blocking != blocking)
  84           {
  85             implConfigureBlocking(blocking);
  86             this.blocking = blocking;
  87           }
  88       }
  89
  90     return this;
  91   }
  92
  93   /**
  94    * Closes this channel.
  95    *
  96    * @exception IOException If an error occurs
  97    */
  98   protected final void implCloseChannel () throws IOException
  99   {
 100     implCloseSelectableChannel ();
 101   }
 102
 103   /**
 104    * Closes this selectable channel.
 105    */
 106   protected abstract void implCloseSelectableChannel () throws IOException;
 107
 108   /**
 109    * Adjusts this channel's blocking mode.
 110    */
 111   protected abstract void implConfigureBlocking (boolean block)
 112     throws IOException;
 113
 114   /**
 115    * Tells whether or not every I/O operation on this channel will block
 116    * until it completes.
 117    */
 118   public final boolean isBlocking()
 119   {
 120     return blocking;
 121   }
 122
 123   /**
 124    * Tells whether or not this channel is currently registered with
 125    * any selectors.
 126    */
 127   public final boolean isRegistered()
 128   {
 129     return !keys.isEmpty();
 130   }
 131
 132   /**
 133    * Retrieves the key representing the channel's registration with the
 134    * given selector.
 135    */
 136   public final SelectionKey keyFor(Selector selector)
 137   {
 138     try
 139       {
 140         return register (selector, 0, null);
 141       }
 142     catch (Exception e)
 143       {
 144         return null;
 145       }
 146   }
 147
 148   /**
 149    * Returns the provider that created this channel.
 150    */
 151   public final SelectorProvider provider ()
 152   {
 153     return provider;
 154   }
 155
 156   private SelectionKey locate (Selector selector)
 157   {
 158     if (keys == null)
 159       return null;
 160
 161     ListIterator it = keys.listIterator ();
 162
 163     while (it.hasNext ())
 164       {
 165         SelectionKey key = (SelectionKey) it.next();
 166
 167         if (key.selector() == selector)
 168           return key;
 169       }
 170
 171     return null;
 172   }
 173
 174   private void add (SelectionKey key)
 175   {
 176     keys.add (key);
 177   }
 178
 179   /**
 180    * Registers this channel with the given selector, returning a selection key.
 181    *
 182    * @exception ClosedChannelException If the channel is already closed.
 183    */
 184   public final SelectionKey register (Selector selin, int ops, Object att)
 185     throws ClosedChannelException
 186   {
 187     if (!isOpen ())
 188       throw new ClosedChannelException();
 189
 190     SelectionKey key = null;
 191     AbstractSelector selector = (AbstractSelector) selin;
 192
 193     synchronized (blockingLock())
 194       {
 195         key = locate (selector);
 196
 197         if (key != null)
 198           {
 199             key.attach (att);
 200           }
 201         else
 202           {
 203             key = selector.register (this, ops, att);
 204
 205             if (key != null)
 206               add (key);
 207           }
 208       }
 209
 210     return key;
 211   }
 212 }