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

   1 /* AbstractSelectableChannel.java
   2    Copyright (C) 2002, 2003, 2004 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
  39 package java.nio.channels.spi;
  40
  41 import java.io.IOException;
  42 import java.nio.channels.ClosedChannelException;
  43 import java.nio.channels.SelectableChannel;
  44 import java.nio.channels.SelectionKey;
  45 import java.nio.channels.Selector;
  46 import java.util.LinkedList;
  47 import java.util.ListIterator;
  48
  49 public abstract class AbstractSelectableChannel extends SelectableChannel
  50 {
  51   private boolean blocking = true;
  52   private Object LOCK = new Object();
  53   private SelectorProvider provider;
  54   private LinkedList keys = new LinkedList();
  55
  56   /**
  57    * Initializes the channel
  58    *
  59    * @param provider the provider that created this channel
  60    */
  61   protected AbstractSelectableChannel(SelectorProvider provider)
  62   {
  63     this.provider = provider;
  64   }
  65
  66   /**
  67    * Retrieves the object upon which the configureBlocking and register
  68    * methods synchronize.
  69    *
  70    * @return the blocking lock
  71    */
  72   public final Object blockingLock()
  73   {
  74     return LOCK;
  75   }
  76
  77   /**
  78    * Adjusts this channel's blocking mode.
  79    *
  80    * @param blocking true if blocking should be enabled, false otherwise
  81    *
  82    * @return this channel
  83    *
  84    * @exception IOException If an error occurs
  85    */
  86   public final SelectableChannel configureBlocking(boolean blocking)
  87     throws IOException
  88   {
  89     synchronized (blockingLock())
  90       {
  91         if (this.blocking != blocking)
  92           {
  93             implConfigureBlocking(blocking);
  94             this.blocking = blocking;
  95           }
  96       }
  97
  98     return this;
  99   }
 100
 101   /**
 102    * Closes this channel.
 103    *
 104    * @exception IOException If an error occurs
 105    */
 106   protected final void implCloseChannel() throws IOException
 107   {
 108     implCloseSelectableChannel();
 109   }
 110
 111   /**
 112    * Closes this selectable channel.
 113    *
 114    * @exception IOException If an error occurs
 115    */
 116   protected abstract void implCloseSelectableChannel()
 117     throws IOException;
 118
 119   /**
 120    * Adjusts this channel's blocking mode.
 121    *
 122    * @param blocking true if blocking should be enabled, false otherwise
 123    *
 124    * @exception IOException If an error occurs
 125    */
 126   protected abstract void implConfigureBlocking(boolean blocking)
 127     throws IOException;
 128
 129   /**
 130    * Tells whether or not every I/O operation on this channel will block
 131    * until it completes.
 132    *
 133    * @return true of this channel is blocking, false otherwise
 134    */
 135   public final boolean isBlocking()
 136   {
 137     return blocking;
 138   }
 139
 140   /**
 141    * Tells whether or not this channel is currently registered with
 142    * any selectors.
 143    *
 144    * @return true if this channel is registered, false otherwise
 145    */
 146   public final boolean isRegistered()
 147   {
 148     return ! keys.isEmpty();
 149   }
 150
 151   /**
 152    * Retrieves the key representing the channel's registration with the
 153    * given selector.
 154    *
 155    * @param selector the selector to get a selection key for
 156    *
 157    * @return the selection key this channel is registered with
 158    */
 159   public final SelectionKey keyFor(Selector selector)
 160   {
 161     if (! isOpen())
 162       return null;
 163
 164     try
 165       {
 166         synchronized (blockingLock())
 167           {
 168             return locate(selector);
 169           }
 170       }
 171     catch (Exception e)
 172       {
 173         return null;
 174       }
 175   }
 176
 177   /**
 178    * Returns the provider that created this channel.
 179    *
 180    * @return the selector provider that created this channel
 181    */
 182   public final SelectorProvider provider()
 183   {
 184     return provider;
 185   }
 186
 187   private SelectionKey locate(Selector selector)
 188   {
 189     ListIterator it = keys.listIterator();
 190
 191     while (it.hasNext())
 192       {
 193         SelectionKey key = (SelectionKey) it.next();
 194
 195         if (key.selector() == selector)
 196           return key;
 197       }
 198
 199     return null;
 200   }
 201
 202   /**
 203    * Registers this channel with the given selector, returning a selection key.
 204    *
 205    * @param selin the seletor to use
 206    * @param ops the interested operations
 207    * @param att an attachment for the returned selection key
 208    *
 209    * @return the registered selection key
 210    *
 211    * @exception ClosedChannelException If the channel is already closed.
 212    */
 213   public final SelectionKey register(Selector selin, int ops, Object att)
 214     throws ClosedChannelException
 215   {
 216     if (! isOpen())
 217       throw new ClosedChannelException();
 218
 219     if ((ops & ~validOps()) != 0)
 220       throw new IllegalArgumentException();
 221
 222     SelectionKey key = null;
 223     AbstractSelector selector = (AbstractSelector) selin;
 224
 225     synchronized (blockingLock())
 226       {
 227         key = locate(selector);
 228
 229         if (key != null && key.isValid())
 230           {
 231             if (att != null)
 232               key.attach(att);
 233           }
 234         else
 235           {
 236             key = selector.register(this, ops, att);
 237
 238             if (key != null)
 239               addSelectionKey(key);
 240           }
 241       }
 242
 243     return key;
 244   }
 245
 246   void addSelectionKey(SelectionKey key)
 247   {
 248     keys.add(key);
 249   }
 250
 251   // This method gets called by AbstractSelector.deregister().
 252   void removeSelectionKey(SelectionKey key)
 253   {
 254     keys.remove(key);
 255   }
 256 }