summaryrefslogtreecommitdiff
path: root/libjava/classpath/gnu/java/nio/SelectorImpl.java
blob: 21238f20f8d5296444c002bad24dbce2139bff79 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
/* SelectorImpl.java --
   Copyright (C) 2002, 2003, 2004, 2006  Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.

As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module.  An independent module is a module which is not derived from
or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so.  If you do not wish to do so, delete this
exception statement from your version. */


package gnu.java.nio;

import java.io.IOException;
import java.nio.channels.ClosedSelectorException;
import java.nio.channels.SelectableChannel;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.nio.channels.spi.AbstractSelectableChannel;
import java.nio.channels.spi.AbstractSelector;
import java.nio.channels.spi.SelectorProvider;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

public class SelectorImpl extends AbstractSelector
{
  private Set<SelectionKey> keys;
  private Set<SelectionKey> selected;

  /**
   * A dummy object whose monitor regulates access to both our
   * selectThread and unhandledWakeup fields.
   */
  private Object selectThreadMutex = new Object ();

  /**
   * Any thread that's currently blocked in a select operation.
   */
  private Thread selectThread;

  /**
   * Indicates whether we have an unhandled wakeup call. This can
   * be due to either wakeup() triggering a thread interruption while
   * a thread was blocked in a select operation (in which case we need
   * to reset this thread's interrupt status after interrupting the
   * select), or else that no thread was on a select operation at the
   * time that wakeup() was called, in which case the following select()
   * operation should return immediately with nothing selected.
   */
  private boolean unhandledWakeup;

  public SelectorImpl (SelectorProvider provider)
  {
    super (provider);

    keys = new HashSet<SelectionKey> ();
    selected = new HashSet<SelectionKey> ();
  }

  protected void finalize() throws Throwable
  {
    close();
  }

  protected final void implCloseSelector()
    throws IOException
  {
    // Cancel any pending select operation.
    wakeup();

    synchronized (keys)
      {
        synchronized (selected)
          {
            synchronized (cancelledKeys ())
              {
                // FIXME: Release resources here.
              }
          }
      }
  }

  public final Set<SelectionKey> keys()
  {
    if (!isOpen())
      throw new ClosedSelectorException();

    return Collections.unmodifiableSet (keys);
  }

  public final int selectNow()
    throws IOException
  {
    // FIXME: We're simulating an immediate select
    // via a select with a timeout of one millisecond.
    return select (1);
  }

  public final int select()
    throws IOException
  {
    return select (0);
  }

  private final int[] getFDsAsArray (int ops)
  {
    int[] result;
    int counter = 0;
    Iterator<SelectionKey> it = keys.iterator ();

    // Count the number of file descriptors needed
    while (it.hasNext ())
      {
        SelectionKeyImpl key = (SelectionKeyImpl) it.next ();

        if ((key.interestOps () & ops) != 0)
          {
            counter++;
          }
      }

    result = new int[counter];

    counter = 0;
    it = keys.iterator ();

    // Fill the array with the file descriptors
    while (it.hasNext ())
      {
        SelectionKeyImpl key = (SelectionKeyImpl) it.next ();

        if ((key.interestOps () & ops) != 0)
          {
            result[counter] = key.getNativeFD();
            counter++;
          }
      }

    return result;
  }

  public synchronized int select (long timeout)
    throws IOException
  {
    if (!isOpen())
      throw new ClosedSelectorException();

    synchronized (keys)
      {
        synchronized (selected)
          {
            deregisterCancelledKeys();

            // Set only keys with the needed interest ops into the arrays.
            int[] read = getFDsAsArray (SelectionKey.OP_READ
                                        | SelectionKey.OP_ACCEPT);
            int[] write = getFDsAsArray (SelectionKey.OP_WRITE
                                         | SelectionKey.OP_CONNECT);

            // FIXME: We dont need to check this yet
            int[] except = new int [0];

            // Test to see if we've got an unhandled wakeup call,
            // in which case we return immediately. Otherwise,
            // remember our current thread and jump into the select.
            // The monitor for dummy object selectThreadMutex regulates
            // access to these fields.

            // FIXME: Not sure from the spec at what point we should
            // return "immediately". Is it here or immediately upon
            // entry to this function?

            // NOTE: There's a possibility of another thread calling
            // wakeup() immediately after our thread releases
            // selectThreadMutex's monitor here, in which case we'll
            // do the select anyway. Since calls to wakeup() and select()
            // among different threads happen in non-deterministic order,
            // I don't think this is an issue.
            synchronized (selectThreadMutex)
              {
                if (unhandledWakeup)
                  {
                    unhandledWakeup = false;
                    return 0;
                  }
                else
                  {
                    selectThread = Thread.currentThread ();
                  }
              }

            // Call the native select() on all file descriptors.
            int result = 0;
            try
              {
                begin();
                result = VMSelector.select (read, write, except, timeout);
              }
            finally
              {
                end();
              }

            // If our unhandled wakeup flag is set at this point,
            // reset our thread's interrupt flag because we were
            // awakened by wakeup() instead of an external thread
            // interruption.
            //
            // NOTE: If we were blocked in a select() and one thread
            // called Thread.interrupt() on the blocked thread followed
            // by another thread calling Selector.wakeup(), then race
            // conditions could make it so that the thread's interrupt
            // flag is reset even though the Thread.interrupt() call
            // "was there first". I don't think we need to care about
            // this scenario.
            synchronized (selectThreadMutex)
              {
                if (unhandledWakeup)
                  {
                    unhandledWakeup = false;
                    Thread.interrupted ();
                  }
                selectThread = null;
              }

            Iterator<SelectionKey> it = keys.iterator ();

            while (it.hasNext ())
              {
                int ops = 0;
                SelectionKeyImpl key = (SelectionKeyImpl) it.next ();

                // If key is already selected retrieve old ready ops.
                if (selected.contains (key))
                  {
                    ops = key.readyOps ();
                  }

                // Set new ready read/accept ops
                for (int i = 0; i < read.length; i++)
                  {
                    if (key.getNativeFD() == read[i])
                      {
                        if (key.channel () instanceof ServerSocketChannelImpl)
                          {
                            ops = ops | SelectionKey.OP_ACCEPT;
                          }
                        else
                          {
                            ops = ops | SelectionKey.OP_READ;
                          }
                      }
                  }

                // Set new ready write ops
                for (int i = 0; i < write.length; i++)
                  {
                    if (key.getNativeFD() == write[i])
                      {
                        if (key.channel() instanceof SocketChannel)
                          {
                            if (((SocketChannel) key.channel ()).isConnected ())
                              ops = ops | SelectionKey.OP_WRITE;
                            else
                              ops = ops | SelectionKey.OP_CONNECT;
                          }
                        else
                          ops = ops | SelectionKey.OP_WRITE;
                      }
                  }

                // FIXME: We dont handle exceptional file descriptors yet.

                // If key is not yet selected add it.
                if (!selected.contains (key))
                  {
                    selected.add (key);
                  }

                // Set new ready ops
                key.readyOps (key.interestOps () & ops);
              }
            deregisterCancelledKeys();

            return result;
          }
        }
  }

  public final Set<SelectionKey> selectedKeys()
  {
    if (!isOpen())
      throw new ClosedSelectorException();

    return selected;
  }

  public final Selector wakeup()
  {
    // IMPLEMENTATION NOTE: Whereas the specification says that
    // thread interruption should trigger a call to wakeup, we
    // do the reverse under the covers: wakeup triggers a thread
    // interrupt followed by a subsequent reset of the thread's
    // interrupt status within select().

    // First, acquire the monitor of the object regulating
    // access to our selectThread and unhandledWakeup fields.
    synchronized (selectThreadMutex)
      {
        unhandledWakeup = true;

        // Interrupt any thread which is currently blocked in
        // a select operation.
        if (selectThread != null)
          selectThread.interrupt ();
      }

    return this;
  }

  private final void deregisterCancelledKeys()
  {
    Set<SelectionKey> ckeys = cancelledKeys ();
    synchronized (ckeys)
    {
      Iterator<SelectionKey> it = ckeys.iterator();

      while (it.hasNext ())
        {
          keys.remove ((SelectionKeyImpl) it.next ());
          it.remove ();
        }
    }
  }

  protected SelectionKey register (SelectableChannel ch, int ops, Object att)
  {
    return register ((AbstractSelectableChannel) ch, ops, att);
  }

  protected final SelectionKey register (AbstractSelectableChannel ch, int ops,
                                         Object att)
  {
    SelectionKeyImpl result;

    if (ch instanceof SocketChannelImpl)
      result = new SocketChannelSelectionKey (ch, this);
    else if (ch instanceof DatagramChannelImpl)
      result = new DatagramChannelSelectionKey (ch, this);
    else if (ch instanceof ServerSocketChannelImpl)
      result = new ServerSocketChannelSelectionKey (ch, this);
    else if (ch instanceof gnu.java.nio.SocketChannelImpl)
      result = new gnu.java.nio.SocketChannelSelectionKeyImpl((gnu.java.nio.SocketChannelImpl)ch, this);
    else
      throw new InternalError ("No known channel type");

    synchronized (keys)
      {
        keys.add (result);

        result.interestOps (ops);
        result.attach (att);
      }

    return result;
  }
}