001 /* AbstractSelectableChannel.java
002 Copyright (C) 2002, 2003, 2004 Free Software Foundation, Inc.
003
004 This file is part of GNU Classpath.
005
006 GNU Classpath is free software; you can redistribute it and/or modify
007 it under the terms of the GNU General Public License as published by
008 the Free Software Foundation; either version 2, or (at your option)
009 any later version.
010
011 GNU Classpath is distributed in the hope that it will be useful, but
012 WITHOUT ANY WARRANTY; without even the implied warranty of
013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014 General Public License for more details.
015
016 You should have received a copy of the GNU General Public License
017 along with GNU Classpath; see the file COPYING. If not, write to the
018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019 02110-1301 USA.
020
021 Linking this library statically or dynamically with other modules is
022 making a combined work based on this library. Thus, the terms and
023 conditions of the GNU General Public License cover the whole
024 combination.
025
026 As a special exception, the copyright holders of this library give you
027 permission to link this library with independent modules to produce an
028 executable, regardless of the license terms of these independent
029 modules, and to copy and distribute the resulting executable under
030 terms of your choice, provided that you also meet, for each linked
031 independent module, the terms and conditions of the license of that
032 module. An independent module is a module which is not derived from
033 or based on this library. If you modify this library, you may extend
034 this exception to your version of the library, but you are not
035 obligated to do so. If you do not wish to do so, delete this
036 exception statement from your version. */
037
038
039 package java.nio.channels.spi;
040
041 import java.io.IOException;
042 import java.nio.channels.ClosedChannelException;
043 import java.nio.channels.SelectableChannel;
044 import java.nio.channels.SelectionKey;
045 import java.nio.channels.Selector;
046 import java.nio.channels.IllegalBlockingModeException;
047 import java.util.Iterator;
048 import java.util.LinkedList;
049 import java.util.ListIterator;
050
051 public abstract class AbstractSelectableChannel extends SelectableChannel
052 {
053 private boolean blocking = true;
054 private Object LOCK = new Object();
055 private SelectorProvider provider;
056 private LinkedList keys = new LinkedList();
057
058 /**
059 * Initializes the channel
060 *
061 * @param provider the provider that created this channel
062 */
063 protected AbstractSelectableChannel(SelectorProvider provider)
064 {
065 this.provider = provider;
066 }
067
068 /**
069 * Retrieves the object upon which the configureBlocking and register
070 * methods synchronize.
071 *
072 * @return the blocking lock
073 */
074 public final Object blockingLock()
075 {
076 return LOCK;
077 }
078
079 /**
080 * Adjusts this channel's blocking mode.
081 *
082 * @param blocking true if blocking should be enabled, false otherwise
083 *
084 * @return this channel
085 *
086 * @exception IOException If an error occurs
087 */
088 public final SelectableChannel configureBlocking(boolean blocking)
089 throws IOException
090 {
091 synchronized (blockingLock())
092 {
093 if (this.blocking != blocking)
094 {
095 implConfigureBlocking(blocking);
096 this.blocking = blocking;
097 }
098 }
099
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 }