Source for java.lang.Runtime

   1: /* Runtime.java -- access to the VM process
   2:    Copyright (C) 1998, 2002, 2003, 2004, 2005 Free Software Foundation
   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.lang;
  40: 
  41: import gnu.classpath.SystemProperties;
  42: import gnu.classpath.VMStackWalker;
  43: 
  44: import java.io.File;
  45: import java.io.IOException;
  46: import java.io.InputStream;
  47: import java.io.OutputStream;
  48: import java.util.HashSet;
  49: import java.util.Iterator;
  50: import java.util.Set;
  51: import java.util.StringTokenizer;
  52: 
  53: /**
  54:  * Runtime represents the Virtual Machine.
  55:  *
  56:  * @author John Keiser
  57:  * @author Eric Blake (ebb9@email.byu.edu)
  58:  * @author Jeroen Frijters
  59:  */
  60: // No idea why this class isn't final, since you can't build a subclass!
  61: public class Runtime
  62: {
  63:   /**
  64:    * The library path, to search when loading libraries. We can also safely use
  65:    * this as a lock for synchronization.
  66:    */
  67:   private final String[] libpath;
  68: 
  69:   /**
  70:    * The thread that started the exit sequence. Access to this field must
  71:    * be thread-safe; lock on libpath to avoid deadlock with user code.
  72:    * <code>runFinalization()</code> may want to look at this to see if ALL
  73:    * finalizers should be run, because the virtual machine is about to halt.
  74:    */
  75:   private Thread exitSequence;
  76: 
  77:   /**
  78:    * All shutdown hooks. This is initialized lazily, and set to null once all
  79:    * shutdown hooks have run. Access to this field must be thread-safe; lock
  80:    * on libpath to avoid deadlock with user code.
  81:    */
  82:   private Set shutdownHooks;
  83: 
  84:   /**
  85:    * The one and only runtime instance.
  86:    */
  87:   private static final Runtime current = new Runtime();
  88: 
  89:   /**
  90:    * Not instantiable by a user, this should only create one instance.
  91:    */
  92:   private Runtime()
  93:   {
  94:     if (current != null)
  95:       throw new InternalError("Attempt to recreate Runtime");
  96:     
  97:     // If used by underlying VM this contains the directories where Classpath's own
  98:     // native libraries are located.
  99:     String bootPath = SystemProperties.getProperty("gnu.classpath.boot.library.path", "");
 100:     
 101:     // If properly set by the user this contains the directories where the application's
 102:     // native libraries are located. On operating systems where a LD_LIBRARY_PATH environment
 103:     // variable is available a VM should preset java.library.path with value of this
 104:     // variable.
 105:     String path = SystemProperties.getProperty("java.library.path", ".");
 106:     String pathSep = SystemProperties.getProperty("path.separator", ":");
 107:     String fileSep = SystemProperties.getProperty("file.separator", "/");
 108: 
 109:     StringTokenizer t1 = new StringTokenizer(bootPath, pathSep);
 110:     StringTokenizer t2 = new StringTokenizer(path, pathSep);
 111:     libpath = new String[t1.countTokens() + t2.countTokens()];
 112:     
 113:     int i = 0;
 114:     while(t1.hasMoreTokens()) {
 115:       String prefix = t1.nextToken();
 116:       if (! prefix.endsWith(fileSep))
 117:         prefix += fileSep;
 118:       
 119:       libpath[i] = prefix;
 120:       i++;
 121:     }
 122:     
 123:     while(t2.hasMoreTokens()) {
 124:       String prefix = t2.nextToken();
 125:       if (! prefix.endsWith(fileSep))
 126:         prefix += fileSep;
 127:   
 128:       libpath[i] = prefix;
 129:       i++;
 130:     }
 131:   }
 132: 
 133:   /**
 134:    * Get the current Runtime object for this JVM. This is necessary to access
 135:    * the many instance methods of this class.
 136:    *
 137:    * @return the current Runtime object
 138:    */
 139:   public static Runtime getRuntime()
 140:   {
 141:     return current;
 142:   }
 143: 
 144:   /**
 145:    * Exit the Java runtime. This method will either throw a SecurityException
 146:    * or it will never return. The status code is returned to the system; often
 147:    * a non-zero status code indicates an abnormal exit. Of course, there is a
 148:    * security check, <code>checkExit(status)</code>.
 149:    *
 150:    * <p>First, all shutdown hooks are run, in unspecified order, and
 151:    * concurrently. Next, if finalization on exit has been enabled, all pending
 152:    * finalizers are run. Finally, the system calls <code>halt</code>.</p>
 153:    *
 154:    * <p>If this is run a second time after shutdown has already started, there
 155:    * are two actions. If shutdown hooks are still executing, it blocks
 156:    * indefinitely. Otherwise, if the status is nonzero it halts immediately;
 157:    * if it is zero, it blocks indefinitely. This is typically called by
 158:    * <code>System.exit</code>.</p>
 159:    *
 160:    * @param status the status to exit with
 161:    * @throws SecurityException if permission is denied
 162:    * @see #addShutdownHook(Thread)
 163:    * @see #runFinalizersOnExit(boolean)
 164:    * @see #runFinalization()
 165:    * @see #halt(int)
 166:    */
 167:   public void exit(int status)
 168:   {
 169:     SecurityManager sm = SecurityManager.current; // Be thread-safe!
 170:     if (sm != null)
 171:       sm.checkExit(status);
 172: 
 173:     if (runShutdownHooks())
 174:       halt(status);
 175: 
 176:     // Someone else already called runShutdownHooks().
 177:     // Make sure we are not/no longer in the shutdownHooks set.
 178:     // And wait till the thread that is calling runShutdownHooks() finishes.
 179:     synchronized (libpath)
 180:       {
 181:         if (shutdownHooks != null)
 182:           {
 183:             shutdownHooks.remove(Thread.currentThread());
 184:             // Interrupt the exit sequence thread, in case it was waiting
 185:             // inside a join on our thread.
 186:             exitSequence.interrupt();
 187:             // Shutdown hooks are still running, so we clear status to
 188:         // make sure we don't halt.
 189:         status = 0;
 190:           }
 191:       }
 192: 
 193:     // If exit() is called again after the shutdown hooks have run, but
 194:     // while finalization for exit is going on and the status is non-zero
 195:     // we halt immediately.
 196:     if (status != 0)
 197:       halt(status);
 198: 
 199:     while (true)
 200:       try
 201:         {
 202:           exitSequence.join();
 203:         }
 204:       catch (InterruptedException e)
 205:         {
 206:           // Ignore, we've suspended indefinitely to let all shutdown
 207:           // hooks complete, and to let any non-zero exits through, because
 208:           // this is a duplicate call to exit(0).
 209:         }
 210:   }
 211: 
 212:   /**
 213:    * On first invocation, run all the shutdown hooks and return true.
 214:    * Any subsequent invocations will simply return false.
 215:    * Note that it is package accessible so that VMRuntime can call it
 216:    * when VM exit is not triggered by a call to Runtime.exit().
 217:    * 
 218:    * @return was the current thread the first one to call this method?
 219:    */
 220:   boolean runShutdownHooks()
 221:   {
 222:     boolean first = false;
 223:     synchronized (libpath) // Synch on libpath, not this, to avoid deadlock.
 224:       {
 225:         if (exitSequence == null)
 226:           {
 227:             first = true;
 228:             exitSequence = Thread.currentThread();
 229:             if (shutdownHooks != null)
 230:               {
 231:                 Iterator i = shutdownHooks.iterator();
 232:                 while (i.hasNext()) // Start all shutdown hooks.
 233:                   try
 234:                     {
 235:                       ((Thread) i.next()).start();
 236:                     }
 237:                   catch (IllegalThreadStateException e)
 238:                     {
 239:                       i.remove();
 240:                     }
 241:               }
 242:           }
 243:       }
 244:     if (first)
 245:       {
 246:         if (shutdownHooks != null)
 247:           {
 248:             // Check progress of all shutdown hooks. As a hook completes,
 249:             // remove it from the set. If a hook calls exit, it removes
 250:             // itself from the set, then waits indefinitely on the
 251:             // exitSequence thread. Once the set is empty, set it to null to
 252:             // signal all finalizer threads that halt may be called.
 253:             while (true)
 254:               {
 255:                 Thread[] hooks;
 256:                 synchronized (libpath)
 257:                   {
 258:                     hooks = new Thread[shutdownHooks.size()];
 259:                     shutdownHooks.toArray(hooks);
 260:                   }
 261:                 if (hooks.length == 0)
 262:                   break;
 263:                 for (int i = 0; i < hooks.length; i++)
 264:                   {
 265:                     try
 266:                       {
 267:                         synchronized (libpath)
 268:                           {
 269:                             if (!shutdownHooks.contains(hooks[i]))
 270:                               continue;
 271:                           }
 272:                         hooks[i].join();
 273:                         synchronized (libpath)
 274:                           {
 275:                             shutdownHooks.remove(hooks[i]);
 276:                           }
 277:                       }
 278:                     catch (InterruptedException x)
 279:                       {
 280:                         // continue waiting on the next thread
 281:                       }
 282:                   }
 283:               }
 284:             synchronized (libpath)
 285:               {
 286:                 shutdownHooks = null;
 287:               }
 288:           }
 289:     // Run finalization on all finalizable objects (even if they are
 290:     // still reachable).
 291:         VMRuntime.runFinalizationForExit();
 292:       }
 293:     return first;
 294:   }
 295: 
 296:   /**
 297:    * Register a new shutdown hook. This is invoked when the program exits
 298:    * normally (because all non-daemon threads ended, or because
 299:    * <code>System.exit</code> was invoked), or when the user terminates
 300:    * the virtual machine (such as by typing ^C, or logging off). There is
 301:    * a security check to add hooks,
 302:    * <code>RuntimePermission("shutdownHooks")</code>.
 303:    *
 304:    * <p>The hook must be an initialized, but unstarted Thread. The threads
 305:    * are run concurrently, and started in an arbitrary order; and user
 306:    * threads or daemons may still be running. Once shutdown hooks have
 307:    * started, they must all complete, or else you must use <code>halt</code>,
 308:    * to actually finish the shutdown sequence. Attempts to modify hooks
 309:    * after shutdown has started result in IllegalStateExceptions.</p>
 310:    *
 311:    * <p>It is imperative that you code shutdown hooks defensively, as you
 312:    * do not want to deadlock, and have no idea what other hooks will be
 313:    * running concurrently. It is also a good idea to finish quickly, as the
 314:    * virtual machine really wants to shut down!</p>
 315:    *
 316:    * <p>There are no guarantees that such hooks will run, as there are ways
 317:    * to forcibly kill a process. But in such a drastic case, shutdown hooks
 318:    * would do little for you in the first place.</p>
 319:    *
 320:    * @param hook an initialized, unstarted Thread
 321:    * @throws IllegalArgumentException if the hook is already registered or run
 322:    * @throws IllegalStateException if the virtual machine is already in
 323:    *         the shutdown sequence
 324:    * @throws SecurityException if permission is denied
 325:    * @since 1.3
 326:    * @see #removeShutdownHook(Thread)
 327:    * @see #exit(int)
 328:    * @see #halt(int)
 329:    */
 330:   public void addShutdownHook(Thread hook)
 331:   {
 332:     SecurityManager sm = SecurityManager.current; // Be thread-safe!
 333:     if (sm != null)
 334:       sm.checkPermission(new RuntimePermission("shutdownHooks"));
 335:     if (hook.isAlive() || hook.getThreadGroup() == null)
 336:       throw new IllegalArgumentException("The hook thread " + hook + " must not have been already run or started");
 337:     synchronized (libpath)
 338:       {
 339:         if (exitSequence != null)
 340:           throw new IllegalStateException("The Virtual Machine is exiting. It is not possible anymore to add any hooks");
 341:         if (shutdownHooks == null)
 342:           {
 343:             VMRuntime.enableShutdownHooks();
 344:             shutdownHooks = new HashSet(); // Lazy initialization.
 345:           }
 346:         if (! shutdownHooks.add(hook))
 347:           throw new IllegalArgumentException(hook.toString() + " had already been inserted");
 348:       }
 349:   }
 350: 
 351:   /**
 352:    * De-register a shutdown hook. As when you registered it, there is a
 353:    * security check to remove hooks,
 354:    * <code>RuntimePermission("shutdownHooks")</code>.
 355:    *
 356:    * @param hook the hook to remove
 357:    * @return true if the hook was successfully removed, false if it was not
 358:    *         registered in the first place
 359:    * @throws IllegalStateException if the virtual machine is already in
 360:    *         the shutdown sequence
 361:    * @throws SecurityException if permission is denied
 362:    * @since 1.3
 363:    * @see #addShutdownHook(Thread)
 364:    * @see #exit(int)
 365:    * @see #halt(int)
 366:    */
 367:   public boolean removeShutdownHook(Thread hook)
 368:   {
 369:     SecurityManager sm = SecurityManager.current; // Be thread-safe!
 370:     if (sm != null)
 371:       sm.checkPermission(new RuntimePermission("shutdownHooks"));
 372:     synchronized (libpath)
 373:       {
 374:         if (exitSequence != null)
 375:           throw new IllegalStateException();
 376:         if (shutdownHooks != null)
 377:           return shutdownHooks.remove(hook);
 378:       }
 379:     return false;
 380:   }
 381: 
 382:   /**
 383:    * Forcibly terminate the virtual machine. This call never returns. It is
 384:    * much more severe than <code>exit</code>, as it bypasses all shutdown
 385:    * hooks and initializers. Use caution in calling this! Of course, there is
 386:    * a security check, <code>checkExit(status)</code>.
 387:    *
 388:    * @param status the status to exit with
 389:    * @throws SecurityException if permission is denied
 390:    * @since 1.3
 391:    * @see #exit(int)
 392:    * @see #addShutdownHook(Thread)
 393:    */
 394:   public void halt(int status)
 395:   {
 396:     SecurityManager sm = SecurityManager.current; // Be thread-safe!
 397:     if (sm != null)
 398:       sm.checkExit(status);
 399:     VMRuntime.exit(status);
 400:   }
 401: 
 402:   /**
 403:    * Tell the VM to run the finalize() method on every single Object before
 404:    * it exits.  Note that the JVM may still exit abnormally and not perform
 405:    * this, so you still don't have a guarantee. And besides that, this is
 406:    * inherently unsafe in multi-threaded code, as it may result in deadlock
 407:    * as multiple threads compete to manipulate objects. This value defaults to
 408:    * <code>false</code>. There is a security check, <code>checkExit(0)</code>.
 409:    *
 410:    * @param finalizeOnExit whether to finalize all Objects on exit
 411:    * @throws SecurityException if permission is denied
 412:    * @see #exit(int)
 413:    * @see #gc()
 414:    * @since 1.1
 415:    * @deprecated never rely on finalizers to do a clean, thread-safe,
 416:    *             mop-up from your code
 417:    */
 418:   public static void runFinalizersOnExit(boolean finalizeOnExit)
 419:   {
 420:     SecurityManager sm = SecurityManager.current; // Be thread-safe!
 421:     if (sm != null)
 422:       sm.checkExit(0);
 423:     VMRuntime.runFinalizersOnExit(finalizeOnExit);
 424:   }
 425: 
 426:   /**
 427:    * Create a new subprocess with the specified command line. Calls
 428:    * <code>exec(cmdline, null, null)</code>. A security check is performed,
 429:    * <code>checkExec</code>.
 430:    *
 431:    * @param cmdline the command to call
 432:    * @return the Process object
 433:    * @throws SecurityException if permission is denied
 434:    * @throws IOException if an I/O error occurs
 435:    * @throws NullPointerException if cmdline is null
 436:    * @throws IndexOutOfBoundsException if cmdline is ""
 437:    */
 438:   public Process exec(String cmdline) throws IOException
 439:   {
 440:     return exec(cmdline, null, null);
 441:   }
 442: 
 443:   /**
 444:    * Create a new subprocess with the specified command line and environment.
 445:    * If the environment is null, the process inherits the environment of
 446:    * this process. Calls <code>exec(cmdline, env, null)</code>. A security
 447:    * check is performed, <code>checkExec</code>.
 448:    *
 449:    * @param cmdline the command to call
 450:    * @param env the environment to use, in the format name=value
 451:    * @return the Process object
 452:    * @throws SecurityException if permission is denied
 453:    * @throws IOException if an I/O error occurs
 454:    * @throws NullPointerException if cmdline is null, or env has null entries
 455:    * @throws IndexOutOfBoundsException if cmdline is ""
 456:    */
 457:   public Process exec(String cmdline, String[] env) throws IOException
 458:   {
 459:     return exec(cmdline, env, null);
 460:   }
 461: 
 462:   /**
 463:    * Create a new subprocess with the specified command line, environment, and
 464:    * working directory. If the environment is null, the process inherits the
 465:    * environment of this process. If the directory is null, the process uses
 466:    * the current working directory. This splits cmdline into an array, using
 467:    * the default StringTokenizer, then calls
 468:    * <code>exec(cmdArray, env, dir)</code>. A security check is performed,
 469:    * <code>checkExec</code>.
 470:    *
 471:    * @param cmdline the command to call
 472:    * @param env the environment to use, in the format name=value
 473:    * @param dir the working directory to use
 474:    * @return the Process object
 475:    * @throws SecurityException if permission is denied
 476:    * @throws IOException if an I/O error occurs
 477:    * @throws NullPointerException if cmdline is null, or env has null entries
 478:    * @throws IndexOutOfBoundsException if cmdline is ""
 479:    * @since 1.3
 480:    */
 481:   public Process exec(String cmdline, String[] env, File dir)
 482:     throws IOException
 483:   {
 484:     StringTokenizer t = new StringTokenizer(cmdline);
 485:     String[] cmd = new String[t.countTokens()];
 486:     for (int i = 0; i < cmd.length; i++)
 487:       cmd[i] = t.nextToken();
 488:     return exec(cmd, env, dir);
 489:   }
 490: 
 491:   /**
 492:    * Create a new subprocess with the specified command line, already
 493:    * tokenized. Calls <code>exec(cmd, null, null)</code>. A security check
 494:    * is performed, <code>checkExec</code>.
 495:    *
 496:    * @param cmd the command to call
 497:    * @return the Process object
 498:    * @throws SecurityException if permission is denied
 499:    * @throws IOException if an I/O error occurs
 500:    * @throws NullPointerException if cmd is null, or has null entries
 501:    * @throws IndexOutOfBoundsException if cmd is length 0
 502:    */
 503:   public Process exec(String[] cmd) throws IOException
 504:   {
 505:     return exec(cmd, null, null);
 506:   }
 507: 
 508:   /**
 509:    * Create a new subprocess with the specified command line, already
 510:    * tokenized, and specified environment. If the environment is null, the
 511:    * process inherits the environment of this process. Calls
 512:    * <code>exec(cmd, env, null)</code>. A security check is performed,
 513:    * <code>checkExec</code>.
 514:    *
 515:    * @param cmd the command to call
 516:    * @param env the environment to use, in the format name=value
 517:    * @return the Process object
 518:    * @throws SecurityException if permission is denied
 519:    * @throws IOException if an I/O error occurs
 520:    * @throws NullPointerException if cmd is null, or cmd or env has null
 521:    *         entries
 522:    * @throws IndexOutOfBoundsException if cmd is length 0
 523:    */
 524:   public Process exec(String[] cmd, String[] env) throws IOException
 525:   {
 526:     return exec(cmd, env, null);
 527:   }
 528: 
 529:   /**
 530:    * Create a new subprocess with the specified command line, already
 531:    * tokenized, and the specified environment and working directory. If the
 532:    * environment is null, the process inherits the environment of this
 533:    * process. If the directory is null, the process uses the current working
 534:    * directory. A security check is performed, <code>checkExec</code>.
 535:    *
 536:    * @param cmd the command to call
 537:    * @param env the environment to use, in the format name=value
 538:    * @param dir the working directory to use
 539:    * @return the Process object
 540:    * @throws SecurityException if permission is denied
 541:    * @throws IOException if an I/O error occurs
 542:    * @throws NullPointerException if cmd is null, or cmd or env has null
 543:    *         entries
 544:    * @throws IndexOutOfBoundsException if cmd is length 0
 545:    * @since 1.3
 546:    */
 547:   public Process exec(String[] cmd, String[] env, File dir)
 548:     throws IOException
 549:   {
 550:     SecurityManager sm = SecurityManager.current; // Be thread-safe!
 551:     if (sm != null)
 552:       sm.checkExec(cmd[0]);
 553:     return VMRuntime.exec(cmd, env, dir);
 554:   }
 555: 
 556:   /**
 557:    * Returns the number of available processors currently available to the
 558:    * virtual machine. This number may change over time; so a multi-processor
 559:    * program want to poll this to determine maximal resource usage.
 560:    *
 561:    * @return the number of processors available, at least 1
 562:    */
 563:   public int availableProcessors()
 564:   {
 565:     return VMRuntime.availableProcessors();
 566:   }
 567: 
 568:   /**
 569:    * Find out how much memory is still free for allocating Objects on the heap.
 570:    *
 571:    * @return the number of bytes of free memory for more Objects
 572:    */
 573:   public long freeMemory()
 574:   {
 575:     return VMRuntime.freeMemory();
 576:   }
 577: 
 578:   /**
 579:    * Find out how much memory total is available on the heap for allocating
 580:    * Objects.
 581:    *
 582:    * @return the total number of bytes of memory for Objects
 583:    */
 584:   public long totalMemory()
 585:   {
 586:     return VMRuntime.totalMemory();
 587:   }
 588: 
 589:   /**
 590:    * Returns the maximum amount of memory the virtual machine can attempt to
 591:    * use. This may be <code>Long.MAX_VALUE</code> if there is no inherent
 592:    * limit (or if you really do have a 8 exabyte memory!).
 593:    *
 594:    * @return the maximum number of bytes the virtual machine will attempt
 595:    *         to allocate
 596:    */
 597:   public long maxMemory()
 598:   {
 599:     return VMRuntime.maxMemory();
 600:   }
 601: 
 602:   /**
 603:    * Run the garbage collector. This method is more of a suggestion than
 604:    * anything. All this method guarantees is that the garbage collector will
 605:    * have "done its best" by the time it returns. Notice that garbage
 606:    * collection takes place even without calling this method.
 607:    */
 608:   public void gc()
 609:   {
 610:     VMRuntime.gc();
 611:   }
 612: 
 613:   /**
 614:    * Run finalization on all Objects that are waiting to be finalized. Again,
 615:    * a suggestion, though a stronger one than {@link #gc()}. This calls the
 616:    * <code>finalize</code> method of all objects waiting to be collected.
 617:    *
 618:    * @see #finalize()
 619:    */
 620:   public void runFinalization()
 621:   {
 622:     VMRuntime.runFinalization();
 623:   }
 624: 
 625:   /**
 626:    * Tell the VM to trace every bytecode instruction that executes (print out
 627:    * a trace of it).  No guarantees are made as to where it will be printed,
 628:    * and the VM is allowed to ignore this request.
 629:    *
 630:    * @param on whether to turn instruction tracing on
 631:    */
 632:   public void traceInstructions(boolean on)
 633:   {
 634:     VMRuntime.traceInstructions(on);
 635:   }
 636: 
 637:   /**
 638:    * Tell the VM to trace every method call that executes (print out a trace
 639:    * of it).  No guarantees are made as to where it will be printed, and the
 640:    * VM is allowed to ignore this request.
 641:    *
 642:    * @param on whether to turn method tracing on
 643:    */
 644:   public void traceMethodCalls(boolean on)
 645:   {
 646:     VMRuntime.traceMethodCalls(on);
 647:   }
 648: 
 649:   /**
 650:    * Load a native library using the system-dependent filename. This is similar
 651:    * to loadLibrary, except the only name mangling done is inserting "_g"
 652:    * before the final ".so" if the VM was invoked by the name "java_g". There
 653:    * may be a security check, of <code>checkLink</code>.
 654:    *
 655:    * <p>
 656:    * The library is loaded using the class loader associated with the
 657:    * class associated with the invoking method.
 658:    *
 659:    * @param filename the file to load
 660:    * @throws SecurityException if permission is denied
 661:    * @throws UnsatisfiedLinkError if the library is not found
 662:    */
 663:   public void load(String filename)
 664:   {
 665:     load(filename, VMStackWalker.getCallingClassLoader());
 666:   }
 667: 
 668:   /**
 669:    * Same as <code>load(String)</code> but using the given loader.
 670:    *
 671:    * @param filename the file to load
 672:    * @param loader class loader, or <code>null</code> for the boot loader
 673:    * @throws SecurityException if permission is denied
 674:    * @throws UnsatisfiedLinkError if the library is not found
 675:    */
 676:   void load(String filename, ClassLoader loader)
 677:   {
 678:     SecurityManager sm = SecurityManager.current; // Be thread-safe!
 679:     if (sm != null)
 680:       sm.checkLink(filename);
 681:     if (loadLib(filename, loader) == 0)
 682:       throw new UnsatisfiedLinkError("Could not load library " + filename);
 683:   }
 684: 
 685:   /**
 686:    * Do a security check on the filename and then load the native library.
 687:    *
 688:    * @param filename the file to load
 689:    * @param loader class loader, or <code>null</code> for the boot loader
 690:    * @return 0 on failure, nonzero on success
 691:    * @throws SecurityException if file read permission is denied
 692:    */
 693:   private static int loadLib(String filename, ClassLoader loader)
 694:   {
 695:     SecurityManager sm = SecurityManager.current; // Be thread-safe!
 696:     if (sm != null)
 697:       sm.checkRead(filename);
 698:     return VMRuntime.nativeLoad(filename, loader);
 699:   }
 700: 
 701:   /**
 702:    * Load a native library using a system-independent "short name" for the
 703:    * library.  It will be transformed to a correct filename in a
 704:    * system-dependent manner (for example, in Windows, "mylib" will be turned
 705:    * into "mylib.dll").  This is done as follows: if the context that called
 706:    * load has a ClassLoader cl, then <code>cl.findLibrary(libpath)</code> is
 707:    * used to convert the name. If that result was null, or there was no class
 708:    * loader, this searches each directory of the system property
 709:    * <code>java.library.path</code> for a file named
 710:    * <code>System.mapLibraryName(libname)</code>. There may be a security
 711:    * check, of <code>checkLink</code>.
 712:    *
 713:    * <p>Note: Besides <code>java.library.path</code> a VM may chose to search
 714:    * for native libraries in a path that is specified by the
 715:    * <code>gnu.classpath.boot.library.path</code> system property. However
 716:    * this is for internal usage or development of GNU Classpath only.
 717:    * <b>A Java application must not load a non-system library by changing
 718:    * this property otherwise it will break compatibility.</b></p>
 719:    *
 720:    * <p>
 721:    * The library is loaded using the class loader associated with the
 722:    * class associated with the invoking method.
 723:    *
 724:    * @param libname the library to load
 725:    *
 726:    * @throws SecurityException if permission is denied
 727:    * @throws UnsatisfiedLinkError if the library is not found
 728:    *
 729:    * @see System#mapLibraryName(String)
 730:    * @see ClassLoader#findLibrary(String)
 731:    */
 732:   public void loadLibrary(String libname)
 733:   {
 734:     loadLibrary(libname, VMStackWalker.getCallingClassLoader());
 735:   }
 736: 
 737:   /**
 738:    * Same as <code>loadLibrary(String)</code> but using the given loader.
 739:    *
 740:    * @param libname the library to load
 741:    * @param loader class loader, or <code>null</code> for the boot loader
 742:    * @throws SecurityException if permission is denied
 743:    * @throws UnsatisfiedLinkError if the library is not found
 744:    */
 745:   void loadLibrary(String libname, ClassLoader loader)
 746:   {
 747:     SecurityManager sm = SecurityManager.current; // Be thread-safe!
 748:     if (sm != null)
 749:       sm.checkLink(libname);
 750:     String filename;
 751:     if (loader != null && (filename = loader.findLibrary(libname)) != null)
 752:       {
 753:     if (loadLib(filename, loader) != 0)
 754:       return;
 755:       }
 756:     else
 757:       {
 758:     filename = VMRuntime.mapLibraryName(libname);
 759:     for (int i = 0; i < libpath.length; i++)
 760:       if (loadLib(libpath[i] + filename, loader) != 0)
 761:         return;
 762:       }
 763:     throw new UnsatisfiedLinkError("Native library `" + libname
 764:       + "' not found (as file `" + filename + "') in gnu.classpath.boot.library.path and java.library.path");
 765:   }
 766: 
 767:   /**
 768:    * Return a localized version of this InputStream, meaning all characters
 769:    * are localized before they come out the other end.
 770:    *
 771:    * @param in the stream to localize
 772:    * @return the localized stream
 773:    * @deprecated <code>InputStreamReader</code> is the preferred way to read
 774:    *             local encodings
 775:    * @XXX This implementation does not localize, yet.
 776:    */
 777:   public InputStream getLocalizedInputStream(InputStream in)
 778:   {
 779:     return in;
 780:   }
 781: 
 782:   /**
 783:    * Return a localized version of this OutputStream, meaning all characters
 784:    * are localized before they are sent to the other end.
 785:    *
 786:    * @param out the stream to localize
 787:    * @return the localized stream
 788:    * @deprecated <code>OutputStreamWriter</code> is the preferred way to write
 789:    *             local encodings
 790:    * @XXX This implementation does not localize, yet.
 791:    */
 792:   public OutputStream getLocalizedOutputStream(OutputStream out)
 793:   {
 794:     return out;
 795:   }
 796: } // class Runtime