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1 14 jlechner
/* Thread -- an independent thread of executable code
2
   Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
3
   Free Software Foundation
4
 
5
This file is part of GNU Classpath.
6
 
7
GNU Classpath is free software; you can redistribute it and/or modify
8
it under the terms of the GNU General Public License as published by
9
the Free Software Foundation; either version 2, or (at your option)
10
any later version.
11
 
12
GNU Classpath is distributed in the hope that it will be useful, but
13
WITHOUT ANY WARRANTY; without even the implied warranty of
14
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15
General Public License for more details.
16
 
17
You should have received a copy of the GNU General Public License
18
along with GNU Classpath; see the file COPYING.  If not, write to the
19
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
20
02110-1301 USA.
21
 
22
Linking this library statically or dynamically with other modules is
23
making a combined work based on this library.  Thus, the terms and
24
conditions of the GNU General Public License cover the whole
25
combination.
26
 
27
As a special exception, the copyright holders of this library give you
28
permission to link this library with independent modules to produce an
29
executable, regardless of the license terms of these independent
30
modules, and to copy and distribute the resulting executable under
31
terms of your choice, provided that you also meet, for each linked
32
independent module, the terms and conditions of the license of that
33
module.  An independent module is a module which is not derived from
34
or based on this library.  If you modify this library, you may extend
35
this exception to your version of the library, but you are not
36
obligated to do so.  If you do not wish to do so, delete this
37
exception statement from your version. */
38
 
39
 
40
package java.lang;
41
 
42
import gnu.gcj.RawData;
43
import gnu.gcj.RawDataManaged;
44
 
45
/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
46
 * "The Java Language Specification", ISBN 0-201-63451-1
47
 * plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
48
 * Status:  Believed complete to version 1.4, with caveats. We do not
49
 *          implement the deprecated (and dangerous) stop, suspend, and resume
50
 *          methods. Security implementation is not complete.
51
 */
52
 
53
/**
54
 * Thread represents a single thread of execution in the VM. When an
55
 * application VM starts up, it creates a non-daemon Thread which calls the
56
 * main() method of a particular class.  There may be other Threads running,
57
 * such as the garbage collection thread.
58
 *
59
 * <p>Threads have names to identify them.  These names are not necessarily
60
 * unique. Every Thread has a priority, as well, which tells the VM which
61
 * Threads should get more running time. New threads inherit the priority
62
 * and daemon status of the parent thread, by default.
63
 *
64
 * <p>There are two methods of creating a Thread: you may subclass Thread and
65
 * implement the <code>run()</code> method, at which point you may start the
66
 * Thread by calling its <code>start()</code> method, or you may implement
67
 * <code>Runnable</code> in the class you want to use and then call new
68
 * <code>Thread(your_obj).start()</code>.
69
 *
70
 * <p>The virtual machine runs until all non-daemon threads have died (either
71
 * by returning from the run() method as invoked by start(), or by throwing
72
 * an uncaught exception); or until <code>System.exit</code> is called with
73
 * adequate permissions.
74
 *
75
 * <p>It is unclear at what point a Thread should be added to a ThreadGroup,
76
 * and at what point it should be removed. Should it be inserted when it
77
 * starts, or when it is created?  Should it be removed when it is suspended
78
 * or interrupted?  The only thing that is clear is that the Thread should be
79
 * removed when it is stopped.
80
 *
81
 * @author Tom Tromey
82
 * @author John Keiser
83
 * @author Eric Blake (ebb9@email.byu.edu)
84
 * @see Runnable
85
 * @see Runtime#exit(int)
86
 * @see #run()
87
 * @see #start()
88
 * @see ThreadLocal
89
 * @since 1.0
90
 * @status updated to 1.4
91
 */
92
public class Thread implements Runnable
93
{
94
  /** The minimum priority for a Thread. */
95
  public static final int MIN_PRIORITY = 1;
96
 
97
  /** The priority a Thread gets by default. */
98
  public static final int NORM_PRIORITY = 5;
99
 
100
  /** The maximum priority for a Thread. */
101
  public static final int MAX_PRIORITY = 10;
102
 
103
  /**
104
   * The group this thread belongs to. This is set to null by
105
   * ThreadGroup.removeThread when the thread dies.
106
   */
107
  ThreadGroup group;
108
 
109
  /** The object to run(), null if this is the target. */
110
  private Runnable runnable;
111
 
112
  /** The thread name, non-null. */
113
  String name;
114
 
115
  /** Whether the thread is a daemon. */
116
  private boolean daemon;
117
 
118
  /** The thread priority, 1 to 10. */
119
  private int priority;
120
 
121
  boolean interrupt_flag;
122
  private boolean alive_flag;
123
  private boolean startable_flag;
124
 
125
  /** The context classloader for this Thread. */
126
  private ClassLoader contextClassLoader;
127
 
128
  // This describes the top-most interpreter frame for this thread.
129
  RawData interp_frame;
130
 
131
  // Our native data - points to an instance of struct natThread.
132
  private RawDataManaged data;
133
 
134
  /**
135
   * Allocates a new <code>Thread</code> object. This constructor has
136
   * the same effect as <code>Thread(null, null,</code>
137
   * <i>gname</i><code>)</code>, where <b><i>gname</i></b> is
138
   * a newly generated name. Automatically generated names are of the
139
   * form <code>"Thread-"+</code><i>n</i>, where <i>n</i> is an integer.
140
   * <p>
141
   * Threads created this way must have overridden their
142
   * <code>run()</code> method to actually do anything.  An example
143
   * illustrating this method being used follows:
144
   * <p><blockquote><pre>
145
   *     import java.lang.*;
146
   *
147
   *     class plain01 implements Runnable {
148
   *         String name;
149
   *         plain01() {
150
   *             name = null;
151
   *         }
152
   *         plain01(String s) {
153
   *             name = s;
154
   *         }
155
   *         public void run() {
156
   *             if (name == null)
157
   *                 System.out.println("A new thread created");
158
   *             else
159
   *                 System.out.println("A new thread with name " + name +
160
   *                                    " created");
161
   *         }
162
   *     }
163
   *     class threadtest01 {
164
   *         public static void main(String args[] ) {
165
   *             int failed = 0 ;
166
   *
167
   *             <b>Thread t1 = new Thread();</b>
168
   *             if (t1 != null)
169
   *                 System.out.println("new Thread() succeed");
170
   *             else {
171
   *                 System.out.println("new Thread() failed");
172
   *                 failed++;
173
   *             }
174
   *         }
175
   *     }
176
   * </pre></blockquote>
177
   *
178
   * @see     java.lang.Thread#Thread(java.lang.ThreadGroup,
179
   *          java.lang.Runnable, java.lang.String)
180
   */
181
  public Thread()
182
  {
183
    this(null, null, gen_name());
184
  }
185
 
186
  /**
187
   * Allocates a new <code>Thread</code> object. This constructor has
188
   * the same effect as <code>Thread(null, target,</code>
189
   * <i>gname</i><code>)</code>, where <i>gname</i> is
190
   * a newly generated name. Automatically generated names are of the
191
   * form <code>"Thread-"+</code><i>n</i>, where <i>n</i> is an integer.
192
   *
193
   * @param target the object whose <code>run</code> method is called.
194
   * @see java.lang.Thread#Thread(java.lang.ThreadGroup,
195
   *                              java.lang.Runnable, java.lang.String)
196
   */
197
  public Thread(Runnable target)
198
  {
199
    this(null, target, gen_name());
200
  }
201
 
202
  /**
203
   * Allocates a new <code>Thread</code> object. This constructor has
204
   * the same effect as <code>Thread(null, null, name)</code>.
205
   *
206
   * @param   name   the name of the new thread.
207
   * @see     java.lang.Thread#Thread(java.lang.ThreadGroup,
208
   *          java.lang.Runnable, java.lang.String)
209
   */
210
  public Thread(String name)
211
  {
212
    this(null, null, name);
213
  }
214
 
215
  /**
216
   * Allocates a new <code>Thread</code> object. This constructor has
217
   * the same effect as <code>Thread(group, target,</code>
218
   * <i>gname</i><code>)</code>, where <i>gname</i> is
219
   * a newly generated name. Automatically generated names are of the
220
   * form <code>"Thread-"+</code><i>n</i>, where <i>n</i> is an integer.
221
   *
222
   * @param group the group to put the Thread into
223
   * @param target the Runnable object to execute
224
   * @throws SecurityException if this thread cannot access <code>group</code>
225
   * @throws IllegalThreadStateException if group is destroyed
226
   * @see #Thread(ThreadGroup, Runnable, String)
227
   */
228
  public Thread(ThreadGroup group, Runnable target)
229
  {
230
    this(group, target, gen_name());
231
  }
232
 
233
  /**
234
   * Allocates a new <code>Thread</code> object. This constructor has
235
   * the same effect as <code>Thread(group, null, name)</code>
236
   *
237
   * @param group the group to put the Thread into
238
   * @param name the name for the Thread
239
   * @throws NullPointerException if name is null
240
   * @throws SecurityException if this thread cannot access <code>group</code>
241
   * @throws IllegalThreadStateException if group is destroyed
242
   * @see #Thread(ThreadGroup, Runnable, String)
243
   */
244
  public Thread(ThreadGroup group, String name)
245
  {
246
    this(group, null, name);
247
  }
248
 
249
  /**
250
   * Allocates a new <code>Thread</code> object. This constructor has
251
   * the same effect as <code>Thread(null, target, name)</code>.
252
   *
253
   * @param target the Runnable object to execute
254
   * @param name the name for the Thread
255
   * @throws NullPointerException if name is null
256
   * @see #Thread(ThreadGroup, Runnable, String)
257
   */
258
  public Thread(Runnable target, String name)
259
  {
260
    this(null, target, name);
261
  }
262
 
263
  /**
264
   * Allocate a new Thread object, with the specified ThreadGroup and name, and
265
   * using the specified Runnable object's <code>run()</code> method to
266
   * execute.  If the Runnable object is null, <code>this</code> (which is
267
   * a Runnable) is used instead.
268
   *
269
   * <p>If the ThreadGroup is null, the security manager is checked. If a
270
   * manager exists and returns a non-null object for
271
   * <code>getThreadGroup</code>, that group is used; otherwise the group
272
   * of the creating thread is used. Note that the security manager calls
273
   * <code>checkAccess</code> if the ThreadGroup is not null.
274
   *
275
   * <p>The new Thread will inherit its creator's priority and daemon status.
276
   * These can be changed with <code>setPriority</code> and
277
   * <code>setDaemon</code>.
278
   *
279
   * @param group the group to put the Thread into
280
   * @param target the Runnable object to execute
281
   * @param name the name for the Thread
282
   * @throws NullPointerException if name is null
283
   * @throws SecurityException if this thread cannot access <code>group</code>
284
   * @throws IllegalThreadStateException if group is destroyed
285
   * @see Runnable#run()
286
   * @see #run()
287
   * @see #setDaemon(boolean)
288
   * @see #setPriority(int)
289
   * @see SecurityManager#checkAccess(ThreadGroup)
290
   * @see ThreadGroup#checkAccess()
291
   */
292
  public Thread(ThreadGroup group, Runnable target, String name)
293
  {
294
    this(currentThread(), group, target, name);
295
  }
296
 
297
  /**
298
   * Allocate a new Thread object, as if by
299
   * <code>Thread(group, null, name)</code>, and give it the specified stack
300
   * size, in bytes. The stack size is <b>highly platform independent</b>,
301
   * and the virtual machine is free to round up or down, or ignore it
302
   * completely.  A higher value might let you go longer before a
303
   * <code>StackOverflowError</code>, while a lower value might let you go
304
   * longer before an <code>OutOfMemoryError</code>.  Or, it may do absolutely
305
   * nothing! So be careful, and expect to need to tune this value if your
306
   * virtual machine even supports it.
307
   *
308
   * @param group the group to put the Thread into
309
   * @param target the Runnable object to execute
310
   * @param name the name for the Thread
311
   * @param size the stack size, in bytes; 0 to be ignored
312
   * @throws NullPointerException if name is null
313
   * @throws SecurityException if this thread cannot access <code>group</code>
314
   * @throws IllegalThreadStateException if group is destroyed
315
   * @since 1.4
316
   */
317
  public Thread(ThreadGroup group, Runnable target, String name, long size)
318
  {
319
    // Just ignore stackSize for now.
320
    this(currentThread(), group, target, name);
321
  }
322
 
323
  private Thread (Thread current, ThreadGroup g, Runnable r, String n)
324
  {
325
    // Make sure the current thread may create a new thread.
326
    checkAccess();
327
 
328
    // The Class Libraries book says ``threadName cannot be null''.  I
329
    // take this to mean NullPointerException.
330
    if (n == null)
331
      throw new NullPointerException ();
332
 
333
    if (g == null)
334
      {
335
        // If CURRENT is null, then we are bootstrapping the first thread. 
336
        // Use ThreadGroup.root, the main threadgroup.
337
        if (current == null)
338
          group = ThreadGroup.root;
339
        else
340
          group = current.getThreadGroup();
341
      }
342
    else
343
      group = g;
344
 
345
    data = null;
346
    interrupt_flag = false;
347
    alive_flag = false;
348
    startable_flag = true;
349
 
350
    if (current != null)
351
      {
352
        group.checkAccess();
353
 
354
        daemon = current.isDaemon();
355
        int gmax = group.getMaxPriority();
356
        int pri = current.getPriority();
357
        priority = (gmax < pri ? gmax : pri);
358
        contextClassLoader = current.contextClassLoader;
359
        InheritableThreadLocal.newChildThread(this);
360
      }
361
    else
362
      {
363
        daemon = false;
364
        priority = NORM_PRIORITY;
365
      }
366
 
367
    name = n;
368
    group.addThread(this);
369
    runnable = r;
370
 
371
    initialize_native ();
372
  }
373
 
374
  /**
375
   * Get the number of active threads in the current Thread's ThreadGroup.
376
   * This implementation calls
377
   * <code>currentThread().getThreadGroup().activeCount()</code>.
378
   *
379
   * @return the number of active threads in the current ThreadGroup
380
   * @see ThreadGroup#activeCount()
381
   */
382
  public static int activeCount()
383
  {
384
    return currentThread().group.activeCount();
385
  }
386
 
387
  /**
388
   * Check whether the current Thread is allowed to modify this Thread. This
389
   * passes the check on to <code>SecurityManager.checkAccess(this)</code>.
390
   *
391
   * @throws SecurityException if the current Thread cannot modify this Thread
392
   * @see SecurityManager#checkAccess(Thread)
393
   */
394
  public final void checkAccess()
395
  {
396
    SecurityManager sm = System.getSecurityManager();
397
    if (sm != null)
398
      sm.checkAccess(this);
399
  }
400
 
401
  /**
402
   * Count the number of stack frames in this Thread.  The Thread in question
403
   * must be suspended when this occurs.
404
   *
405
   * @return the number of stack frames in this Thread
406
   * @throws IllegalThreadStateException if this Thread is not suspended
407
   * @deprecated pointless, since suspend is deprecated
408
   */
409
  public native int countStackFrames();
410
 
411
  /**
412
   * Get the currently executing Thread.
413
   *
414
   * @return the currently executing Thread
415
   */
416
  public static native Thread currentThread();
417
 
418
  /**
419
   * Originally intended to destroy this thread, this method was never
420
   * implemented by Sun, and is hence a no-op.
421
   */
422
  public void destroy()
423
  {
424
    throw new NoSuchMethodError();
425
  }
426
 
427
  /**
428
   * Print a stack trace of the current thread to stderr using the same
429
   * format as Throwable's printStackTrace() method.
430
   *
431
   * @see Throwable#printStackTrace()
432
   */
433
  public static void dumpStack()
434
  {
435
    (new Exception("Stack trace")).printStackTrace();
436
  }
437
 
438
  /**
439
   * Copy every active thread in the current Thread's ThreadGroup into the
440
   * array. Extra threads are silently ignored. This implementation calls
441
   * <code>getThreadGroup().enumerate(array)</code>, which may have a
442
   * security check, <code>checkAccess(group)</code>.
443
   *
444
   * @param array the array to place the Threads into
445
   * @return the number of Threads placed into the array
446
   * @throws NullPointerException if array is null
447
   * @throws SecurityException if you cannot access the ThreadGroup
448
   * @see ThreadGroup#enumerate(Thread[])
449
   * @see #activeCount()
450
   * @see SecurityManager#checkAccess(ThreadGroup)
451
   */
452
  public static int enumerate(Thread[] array)
453
  {
454
    return currentThread().group.enumerate(array);
455
  }
456
 
457
  /**
458
   * Get this Thread's name.
459
   *
460
   * @return this Thread's name
461
   */
462
  public final String getName()
463
  {
464
    return name;
465
  }
466
 
467
  /**
468
   * Get this Thread's priority.
469
   *
470
   * @return the Thread's priority
471
   */
472
  public final int getPriority()
473
  {
474
    return priority;
475
  }
476
 
477
  /**
478
   * Get the ThreadGroup this Thread belongs to. If the thread has died, this
479
   * returns null.
480
   *
481
   * @return this Thread's ThreadGroup
482
   */
483
  public final ThreadGroup getThreadGroup()
484
  {
485
    return group;
486
  }
487
 
488
  /**
489
   * Checks whether the current thread holds the monitor on a given object.
490
   * This allows you to do <code>assert Thread.holdsLock(obj)</code>.
491
   *
492
   * @param obj the object to test lock ownership on.
493
   * @return true if the current thread is currently synchronized on obj
494
   * @throws NullPointerException if obj is null
495
   * @since 1.4
496
   */
497
  public static native boolean holdsLock(Object obj);
498
 
499
  /**
500
   * Interrupt this Thread. First, there is a security check,
501
   * <code>checkAccess</code>. Then, depending on the current state of the
502
   * thread, various actions take place:
503
   *
504
   * <p>If the thread is waiting because of {@link #wait()},
505
   * {@link #sleep(long)}, or {@link #join()}, its <i>interrupt status</i>
506
   * will be cleared, and an InterruptedException will be thrown. Notice that
507
   * this case is only possible if an external thread called interrupt().
508
   *
509
   * <p>If the thread is blocked in an interruptible I/O operation, in
510
   * {@link java.nio.channels.InterruptibleChannel}, the <i>interrupt
511
   * status</i> will be set, and ClosedByInterruptException will be thrown.
512
   *
513
   * <p>If the thread is blocked on a {@link java.nio.channels.Selector}, the
514
   * <i>interrupt status</i> will be set, and the selection will return, with
515
   * a possible non-zero value, as though by the wakeup() method.
516
   *
517
   * <p>Otherwise, the interrupt status will be set.
518
   *
519
   * @throws SecurityException if you cannot modify this Thread
520
   */
521
  public native void interrupt();
522
 
523
  /**
524
   * Determine whether the current Thread has been interrupted, and clear
525
   * the <i>interrupted status</i> in the process.
526
   *
527
   * @return whether the current Thread has been interrupted
528
   * @see #isInterrupted()
529
   */
530
  public static boolean interrupted()
531
  {
532
    return currentThread().isInterrupted(true);
533
  }
534
 
535
  /**
536
   * Determine whether the given Thread has been interrupted, but leave
537
   * the <i>interrupted status</i> alone in the process.
538
   *
539
   * @return whether the Thread has been interrupted
540
   * @see #interrupted()
541
   */
542
  public boolean isInterrupted()
543
  {
544
    return interrupt_flag;
545
  }
546
 
547
  /**
548
   * Determine whether this Thread is alive. A thread which is alive has
549
   * started and not yet died.
550
   *
551
   * @return whether this Thread is alive
552
   */
553
  public final synchronized boolean isAlive()
554
  {
555
    return alive_flag;
556
  }
557
 
558
  /**
559
   * Tell whether this is a daemon Thread or not.
560
   *
561
   * @return whether this is a daemon Thread or not
562
   * @see #setDaemon(boolean)
563
   */
564
  public final boolean isDaemon()
565
  {
566
    return daemon;
567
  }
568
 
569
  /**
570
   * Wait forever for the Thread in question to die.
571
   *
572
   * @throws InterruptedException if the Thread is interrupted; it's
573
   *         <i>interrupted status</i> will be cleared
574
   */
575
  public final void join() throws InterruptedException
576
  {
577
    join(0, 0);
578
  }
579
 
580
  /**
581
   * Wait the specified amount of time for the Thread in question to die.
582
   *
583
   * @param ms the number of milliseconds to wait, or 0 for forever
584
   * @throws InterruptedException if the Thread is interrupted; it's
585
   *         <i>interrupted status</i> will be cleared
586
   */
587
  public final void join(long ms) throws InterruptedException
588
  {
589
    join(ms, 0);
590
  }
591
 
592
  /**
593
   * Wait the specified amount of time for the Thread in question to die.
594
   *
595
   * <p>Note that 1,000,000 nanoseconds == 1 millisecond, but most VMs do
596
   * not offer that fine a grain of timing resolution. Besides, there is
597
   * no guarantee that this thread can start up immediately when time expires,
598
   * because some other thread may be active.  So don't expect real-time
599
   * performance.
600
   *
601
   * @param ms the number of milliseconds to wait, or 0 for forever
602
   * @param ns the number of extra nanoseconds to sleep (0-999999)
603
   * @throws InterruptedException if the Thread is interrupted; it's
604
   *         <i>interrupted status</i> will be cleared
605
   * @throws IllegalArgumentException if ns is invalid
606
   * @XXX A ThreadListener would be nice, to make this efficient.
607
   */
608
  public final native void join(long ms, int ns)
609
    throws InterruptedException;
610
 
611
  /**
612
   * Resume a suspended thread.
613
   *
614
   * @throws SecurityException if you cannot resume the Thread
615
   * @see #checkAccess()
616
   * @see #suspend()
617
   * @deprecated pointless, since suspend is deprecated
618
   */
619
  public final native void resume();
620
 
621
  private final native void finish_();
622
 
623
  /**
624
   * Determine whether the given Thread has been interrupted, but leave
625
   * the <i>interrupted status</i> alone in the process.
626
   *
627
   * @return whether the current Thread has been interrupted
628
   * @see #interrupted()
629
   */
630
  private boolean isInterrupted(boolean clear_flag)
631
  {
632
    boolean r = interrupt_flag;
633
    if (clear_flag && r)
634
      {
635
        // Only clear the flag if we saw it as set. Otherwise this could 
636
        // potentially cause us to miss an interrupt in a race condition, 
637
        // because this method is not synchronized.
638
        interrupt_flag = false;
639
      }
640
    return r;
641
  }
642
 
643
  /**
644
   * The method of Thread that will be run if there is no Runnable object
645
   * associated with the Thread. Thread's implementation does nothing at all.
646
   *
647
   * @see #start()
648
   * @see #Thread(ThreadGroup, Runnable, String)
649
   */
650
  public void run()
651
  {
652
    if (runnable != null)
653
      runnable.run();
654
  }
655
 
656
  /**
657
   * Set the daemon status of this Thread.  If this is a daemon Thread, then
658
   * the VM may exit even if it is still running.  This may only be called
659
   * before the Thread starts running. There may be a security check,
660
   * <code>checkAccess</code>.
661
   *
662
   * @param daemon whether this should be a daemon thread or not
663
   * @throws SecurityException if you cannot modify this Thread
664
   * @throws IllegalThreadStateException if the Thread is active
665
   * @see #isDaemon()
666
   * @see #checkAccess()
667
   */
668
  public final void setDaemon(boolean daemon)
669
  {
670
    if (!startable_flag)
671
      throw new IllegalThreadStateException();
672
    checkAccess();
673
    this.daemon = daemon;
674
  }
675
 
676
  /**
677
   * Returns the context classloader of this Thread. The context
678
   * classloader can be used by code that want to load classes depending
679
   * on the current thread. Normally classes are loaded depending on
680
   * the classloader of the current class. There may be a security check
681
   * for <code>RuntimePermission("getClassLoader")</code> if the caller's
682
   * class loader is not null or an ancestor of this thread's context class
683
   * loader.
684
   *
685
   * @return the context class loader
686
   * @throws SecurityException when permission is denied
687
   * @see setContextClassLoader(ClassLoader)
688
   * @since 1.2
689
   */
690
  public synchronized ClassLoader getContextClassLoader()
691
  {
692
    if (contextClassLoader == null)
693
      contextClassLoader = ClassLoader.getSystemClassLoader();
694
 
695
    SecurityManager sm = System.getSecurityManager();
696
    // FIXME: we can't currently find the caller's class loader.
697
    ClassLoader callers = null;
698
    if (sm != null && callers != null)
699
      {
700
        // See if the caller's class loader is the same as or an
701
        // ancestor of this thread's class loader.
702
        while (callers != null && callers != contextClassLoader)
703
          {
704
            // FIXME: should use some internal version of getParent
705
            // that avoids security checks.
706
            callers = callers.getParent();
707
          }
708
 
709
        if (callers != contextClassLoader)
710
          sm.checkPermission(new RuntimePermission("getClassLoader"));
711
      }
712
 
713
    return contextClassLoader;
714
  }
715
 
716
  /**
717
   * Sets the context classloader for this Thread. When not explicitly set,
718
   * the context classloader for a thread is the same as the context
719
   * classloader of the thread that created this thread. The first thread has
720
   * as context classloader the system classloader. There may be a security
721
   * check for <code>RuntimePermission("setContextClassLoader")</code>.
722
   *
723
   * @param classloader the new context class loader
724
   * @throws SecurityException when permission is denied
725
   * @see getContextClassLoader()
726
   * @since 1.2
727
   */
728
  public synchronized void setContextClassLoader(ClassLoader classloader)
729
  {
730
    SecurityManager sm = System.getSecurityManager();
731
    if (sm != null)
732
      sm.checkPermission(new RuntimePermission("setContextClassLoader"));
733
    this.contextClassLoader = classloader;
734
  }
735
 
736
  /**
737
   * Set this Thread's name.  There may be a security check,
738
   * <code>checkAccess</code>.
739
   *
740
   * @param name the new name for this Thread
741
   * @throws NullPointerException if name is null
742
   * @throws SecurityException if you cannot modify this Thread
743
   */
744
  public final void setName(String name)
745
  {
746
    checkAccess();
747
    // The Class Libraries book says ``threadName cannot be null''.  I
748
    // take this to mean NullPointerException.
749
    if (name == null)
750
      throw new NullPointerException();
751
    this.name = name;
752
  }
753
 
754
  /**
755
   * Causes the currently executing thread object to temporarily pause
756
   * and allow other threads to execute.
757
   */
758
  public static native void yield();
759
 
760
  /**
761
   * Suspend the current Thread's execution for the specified amount of
762
   * time. The Thread will not lose any locks it has during this time. There
763
   * are no guarantees which thread will be next to run, but most VMs will
764
   * choose the highest priority thread that has been waiting longest.
765
   *
766
   * @param ms the number of milliseconds to sleep, or 0 for forever
767
   * @throws InterruptedException if the Thread is interrupted; it's
768
   *         <i>interrupted status</i> will be cleared
769
   * @see #notify()
770
   * @see #wait(long)
771
   */
772
  public static void sleep(long ms) throws InterruptedException
773
  {
774
    sleep(ms, 0);
775
  }
776
 
777
  /**
778
   * Suspend the current Thread's execution for the specified amount of
779
   * time. The Thread will not lose any locks it has during this time. There
780
   * are no guarantees which thread will be next to run, but most VMs will
781
   * choose the highest priority thread that has been waiting longest.
782
   *
783
   * <p>Note that 1,000,000 nanoseconds == 1 millisecond, but most VMs do
784
   * not offer that fine a grain of timing resolution. Besides, there is
785
   * no guarantee that this thread can start up immediately when time expires,
786
   * because some other thread may be active.  So don't expect real-time
787
   * performance.
788
   *
789
   * @param ms the number of milliseconds to sleep, or 0 for forever
790
   * @param ns the number of extra nanoseconds to sleep (0-999999)
791
   * @throws InterruptedException if the Thread is interrupted; it's
792
   *         <i>interrupted status</i> will be cleared
793
   * @throws IllegalArgumentException if ns is invalid
794
   * @see #notify()
795
   * @see #wait(long, int)
796
   */
797
  public static native void sleep(long timeout, int nanos)
798
    throws InterruptedException;
799
 
800
  /**
801
   * Start this Thread, calling the run() method of the Runnable this Thread
802
   * was created with, or else the run() method of the Thread itself. This
803
   * is the only way to start a new thread; calling run by yourself will just
804
   * stay in the same thread. The virtual machine will remove the thread from
805
   * its thread group when the run() method completes.
806
   *
807
   * @throws IllegalThreadStateException if the thread has already started
808
   * @see #run()
809
   */
810
  public native void start();
811
 
812
  /**
813
   * Cause this Thread to stop abnormally because of the throw of a ThreadDeath
814
   * error. If you stop a Thread that has not yet started, it will stop
815
   * immediately when it is actually started.
816
   *
817
   * <p>This is inherently unsafe, as it can interrupt synchronized blocks and
818
   * leave data in bad states.  Hence, there is a security check:
819
   * <code>checkAccess(this)</code>, plus another one if the current thread
820
   * is not this: <code>RuntimePermission("stopThread")</code>. If you must
821
   * catch a ThreadDeath, be sure to rethrow it after you have cleaned up.
822
   * ThreadDeath is the only exception which does not print a stack trace when
823
   * the thread dies.
824
   *
825
   * @throws SecurityException if you cannot stop the Thread
826
   * @see #interrupt()
827
   * @see #checkAccess()
828
   * @see #start()
829
   * @see ThreadDeath
830
   * @see ThreadGroup#uncaughtException(Thread, Throwable)
831
   * @see SecurityManager#checkAccess(Thread)
832
   * @see SecurityManager#checkPermission(Permission)
833
   * @deprecated unsafe operation, try not to use
834
   */
835
  public final void stop()
836
  {
837
    // Argument doesn't matter, because this is no longer
838
    // supported.
839
    stop(null);
840
  }
841
 
842
  /**
843
   * Cause this Thread to stop abnormally and throw the specified exception.
844
   * If you stop a Thread that has not yet started, it will stop immediately
845
   * when it is actually started. <b>WARNING</b>This bypasses Java security,
846
   * and can throw a checked exception which the call stack is unprepared to
847
   * handle. Do not abuse this power.
848
   *
849
   * <p>This is inherently unsafe, as it can interrupt synchronized blocks and
850
   * leave data in bad states.  Hence, there is a security check:
851
   * <code>checkAccess(this)</code>, plus another one if the current thread
852
   * is not this: <code>RuntimePermission("stopThread")</code>. If you must
853
   * catch a ThreadDeath, be sure to rethrow it after you have cleaned up.
854
   * ThreadDeath is the only exception which does not print a stack trace when
855
   * the thread dies.
856
   *
857
   * @param t the Throwable to throw when the Thread dies
858
   * @throws SecurityException if you cannot stop the Thread
859
   * @throws NullPointerException in the calling thread, if t is null
860
   * @see #interrupt()
861
   * @see #checkAccess()
862
   * @see #start()
863
   * @see ThreadDeath
864
   * @see ThreadGroup#uncaughtException(Thread, Throwable)
865
   * @see SecurityManager#checkAccess(Thread)
866
   * @see SecurityManager#checkPermission(Permission)
867
   * @deprecated unsafe operation, try not to use
868
   */
869
  public final native void stop(Throwable t);
870
 
871
  /**
872
   * Suspend this Thread.  It will not come back, ever, unless it is resumed.
873
   *
874
   * <p>This is inherently unsafe, as the suspended thread still holds locks,
875
   * and can potentially deadlock your program.  Hence, there is a security
876
   * check: <code>checkAccess</code>.
877
   *
878
   * @throws SecurityException if you cannot suspend the Thread
879
   * @see #checkAccess()
880
   * @see #resume()
881
   * @deprecated unsafe operation, try not to use
882
   */
883
  public final native void suspend();
884
 
885
  /**
886
   * Set this Thread's priority. There may be a security check,
887
   * <code>checkAccess</code>, then the priority is set to the smaller of
888
   * priority and the ThreadGroup maximum priority.
889
   *
890
   * @param priority the new priority for this Thread
891
   * @throws IllegalArgumentException if priority exceeds MIN_PRIORITY or
892
   *         MAX_PRIORITY
893
   * @throws SecurityException if you cannot modify this Thread
894
   * @see #getPriority()
895
   * @see #checkAccess()
896
   * @see ThreadGroup#getMaxPriority()
897
   * @see #MIN_PRIORITY
898
   * @see #MAX_PRIORITY
899
   */
900
  public final native void setPriority(int newPriority);
901
 
902
  /**
903
   * Returns a string representation of this thread, including the
904
   * thread's name, priority, and thread group.
905
   *
906
   * @return a human-readable String representing this Thread
907
   */
908
  public String toString()
909
  {
910
    return ("Thread[" + name + "," + priority + ","
911
            + (group == null ? "" : group.getName()) + "]");
912
  }
913
 
914
  private final native void initialize_native();
915
 
916
  private final native static String gen_name();
917
}

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