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

   1 /* AbstractSelectableChannel.java
   2    Copyright (C) 2002 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   int registered;
  52   boolean blocking = true;
  53   Object LOCK = new Object ();
  54   SelectorProvider provider;
  55   List keys;
  56
  57   /**
  58    * Initializes the channel
  59    */
  60   protected AbstractSelectableChannel (SelectorProvider provider)
  61   {
  62     this.provider = provider;
  63   }
  64
  65   /**
  66    * Retrieves the object upon which the configureBlocking and register
  67    * methods synchronize.
  68    */
  69   public final Object blockingLock ()
  70   {
  71     return LOCK;
  72   }
  73
  74   /**
  75    * Adjusts this channel's blocking mode.
  76    */
  77   public final SelectableChannel configureBlocking (boolean block)
  78   {
  79     synchronized (LOCK)
  80       {
  81         blocking = true;
  82         implConfigureBlocking (block);
  83       }
  84
  85     return this;
  86   }
  87
  88   /**
  89    * Closes this channel.
  90    *
  91    * @exception IOException If an error occurs
  92    */
  93   protected final void implCloseChannel ()
  94   {
  95     implCloseSelectableChannel ();
  96   }
  97
  98   /**
  99    * Closes this selectable channel.
 100    */
 101   protected abstract void implCloseSelectableChannel ();
 102
 103   /**
 104    * Adjusts this channel's blocking mode.
 105    */
 106   protected abstract void implConfigureBlocking (boolean block);
 107
 108   /**
 109    * Tells whether or not every I/O operation on this channel will block
 110    * until it completes.
 111    */
 112   public final boolean isBlocking()
 113   {
 114     return blocking;
 115   }
 116
 117   /**
 118    * Tells whether or not this channel is currently registered with
 119    * any selectors.
 120    */
 121   public final boolean isRegistered()
 122   {
 123     return registered > 0;
 124   }
 125
 126   /**
 127    * Retrieves the key representing the channel's registration with the
 128    * given selector.
 129    */
 130   public final SelectionKey keyFor(Selector selector)
 131   {
 132     try
 133       {
 134         return register (selector, 0, null);
 135       }
 136     catch (Exception e)
 137       {
 138         return null;
 139       }
 140   }
 141
 142   /**
 143    * Returns the provider that created this channel.
 144    */
 145   public final SelectorProvider provider ()
 146   {
 147     return provider;
 148   }
 149
 150   private SelectionKey locate (Selector selector)
 151   {
 152     if (keys == null)
 153       return null;
 154
 155     SelectionKey k = null;
 156     ListIterator it = keys.listIterator ();
 157
 158     while (it.hasNext ())
 159       {
 160         k = (SelectionKey) it.next ();
 161         if (k.selector () == selector)
 162           {
 163             return k;
 164           }
 165       }
 166
 167     return k;
 168   }
 169
 170   private void add (SelectionKey key)
 171   {
 172     if (keys == null)
 173       {
 174         keys = new LinkedList ();
 175       }
 176
 177     keys.add (key);
 178   }
 179
 180   /**
 181    * Registers this channel with the given selector, returning a selection key.
 182    *
 183    * @exception ClosedChannelException If the channel is already closed.
 184    */
 185   public final SelectionKey register (Selector selin, int ops, Object att)
 186     throws ClosedChannelException
 187   {
 188     if (!isOpen ())
 189       throw new ClosedChannelException();
 190
 191     SelectionKey k = null;
 192     AbstractSelector selector = (AbstractSelector) selin;
 193
 194     synchronized (LOCK)
 195       {
 196         k = locate (selector);
 197
 198         if (k != null)
 199           {
 200             k.attach (att);
 201           }
 202         else
 203           {
 204             k = selector.register (this, ops, att);
 205
 206             if (k != null)
 207               add (k);
 208           }
 209       }
 210
 211     return k;
 212   }
 213 }