Source for java.nio.channels.spi.AbstractSelectableChannel

   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., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 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.nio.channels.IllegalBlockingModeException;
  47: import java.util.Iterator;
  48: import java.util.LinkedList;
  49: import java.util.ListIterator;
  50: 
  51: public abstract class AbstractSelectableChannel extends SelectableChannel
  52: {
  53:   private boolean blocking = true;
  54:   private Object LOCK = new Object();
  55:   private SelectorProvider provider;
  56:   private LinkedList keys = new LinkedList();
  57: 
  58:   /**
  59:    * Initializes the channel
  60:    *
  61:    * @param provider the provider that created this channel
  62:    */
  63:   protected AbstractSelectableChannel(SelectorProvider provider)
  64:   {
  65:     this.provider = provider;
  66:   }
  67: 
  68:   /**
  69:    * Retrieves the object upon which the configureBlocking and register
  70:    * methods synchronize.
  71:    *
  72:    * @return the blocking lock
  73:    */
  74:   public final Object blockingLock()
  75:   {
  76:     return LOCK;
  77:   }
  78: 
  79:   /**
  80:    * Adjusts this channel's blocking mode.
  81:    *
  82:    * @param blocking true if blocking should be enabled, false otherwise
  83:    *
  84:    * @return this channel
  85:    *
  86:    * @exception IOException If an error occurs
  87:    */
  88:   public final SelectableChannel configureBlocking(boolean blocking)
  89:     throws IOException
  90:   {
  91:     synchronized (blockingLock())
  92:       {
  93:     if (this.blocking != blocking)
  94:       {
  95:         implConfigureBlocking(blocking);
  96:         this.blocking = blocking;
  97:       }
  98:       }
  99: 
 100:     return this;
 101:   }
 102: 
 103:   /**
 104:    * Closes this channel.
 105:    *
 106:    * @exception IOException If an error occurs
 107:    */
 108:   protected final void implCloseChannel() throws IOException
 109:   {
 110:     try
 111:       {
 112:         implCloseSelectableChannel();
 113:       }
 114:     finally
 115:       {
 116:         for (Iterator it = keys.iterator(); it.hasNext(); )
 117:           ((SelectionKey) it.next()).cancel();
 118:       }
 119:   }
 120: 
 121:   /**
 122:    * Closes this selectable channel.
 123:    *
 124:    * @exception IOException If an error occurs
 125:    */
 126:   protected abstract void implCloseSelectableChannel()
 127:     throws IOException;
 128: 
 129:   /**
 130:    * Adjusts this channel's blocking mode.
 131:    *
 132:    * @param blocking true if blocking should be enabled, false otherwise
 133:    *
 134:    * @exception IOException If an error occurs
 135:    */
 136:   protected abstract void implConfigureBlocking(boolean blocking)
 137:     throws IOException;
 138: 
 139:   /**
 140:    * Tells whether or not every I/O operation on this channel will block
 141:    * until it completes.
 142:    *
 143:    * @return true of this channel is blocking, false otherwise
 144:    */
 145:   public final boolean isBlocking()
 146:   {
 147:     return blocking;
 148:   }
 149: 
 150:   /**
 151:    * Tells whether or not this channel is currently registered with
 152:    * any selectors.
 153:    *
 154:    * @return true if this channel is registered, false otherwise
 155:    */
 156:   public final boolean isRegistered()
 157:   {
 158:     return ! keys.isEmpty();
 159:   }
 160: 
 161:   /**
 162:    * Retrieves the key representing the channel's registration with the
 163:    * given selector.
 164:    *
 165:    * @param selector the selector to get a selection key for
 166:    *
 167:    * @return the selection key this channel is registered with
 168:    */
 169:   public final SelectionKey keyFor(Selector selector)
 170:   {
 171:     if (! isOpen())
 172:       return null;
 173: 
 174:     try
 175:       {
 176:     synchronized (blockingLock())
 177:       {
 178:         return locate(selector);
 179:       }
 180:       }
 181:     catch (Exception e)
 182:       {
 183:     return null;
 184:       }
 185:   }
 186: 
 187:   /**
 188:    * Returns the provider that created this channel.
 189:    *
 190:    * @return the selector provider that created this channel
 191:    */
 192:   public final SelectorProvider provider()
 193:   {
 194:     return provider;
 195:   }
 196: 
 197:   private SelectionKey locate(Selector selector)
 198:   {
 199:     ListIterator it = keys.listIterator();
 200: 
 201:     while (it.hasNext())
 202:       {
 203:     SelectionKey key = (SelectionKey) it.next();
 204: 
 205:     if (key.selector() == selector)
 206:       return key;
 207:       }
 208: 
 209:     return null;
 210:   }
 211: 
 212:   /**
 213:    * Registers this channel with the given selector, returning a selection key.
 214:    *
 215:    * @param selin the seletor to use
 216:    * @param ops the interested operations
 217:    * @param att an attachment for the returned selection key
 218:    *
 219:    * @return the registered selection key
 220:    * 
 221:    * @exception ClosedChannelException If the channel is already closed.
 222:    * @exception IllegalBlockingModeException If the channel is configured in
 223:    * blocking mode.
 224:    */
 225:   public final SelectionKey register(Selector selin, int ops, Object att)
 226:     throws ClosedChannelException
 227:   {
 228:     if (! isOpen())
 229:       throw new ClosedChannelException();
 230: 
 231:     if ((ops & ~validOps()) != 0)
 232:       throw new IllegalArgumentException();
 233:     
 234:     SelectionKey key = null;
 235:     AbstractSelector selector = (AbstractSelector) selin;
 236: 
 237:     synchronized (blockingLock())
 238:       {
 239:     if (blocking)
 240:       throw new IllegalBlockingModeException();
 241: 
 242:     key = locate(selector);
 243: 
 244:     if (key != null && key.isValid())
 245:       {
 246:             key.interestOps(ops);
 247:             key.attach(att);
 248:       }
 249:     else
 250:       {
 251:         key = selector.register(this, ops, att);
 252: 
 253:         if (key != null)
 254:           addSelectionKey(key);
 255:       }
 256:       }
 257: 
 258:     return key;
 259:   }
 260: 
 261:   void addSelectionKey(SelectionKey key)
 262:   {
 263:     keys.add(key);
 264:   }
 265: 
 266:   // This method gets called by AbstractSelector.deregister().
 267:   void removeSelectionKey(SelectionKey key)
 268:   {
 269:     keys.remove(key);
 270:   }
 271: }