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root/jsr166/jsr166/src/jsr166y/ForkJoinTask.java

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.17 by jsr166, Sat Jul 25 00:34:00 2009 UTC vs.
Revision 1.25 by dl, Fri Jul 31 16:27:08 2009 UTC

#	Line 25 | Line 25 | import java.util.WeakHashMap;
25		* <p> A "main" ForkJoinTask begins execution when submitted to a
26		* {@link ForkJoinPool}. Once started, it will usually in turn start
27		* other subtasks.  As indicated by the name of this class, many
28	<	* programs using ForkJoinTasks employ only methods {@code fork}
29	<	* and {@code join}, or derivatives such as
30	<	* {@code invokeAll}.  However, this class also provides a number
31	<	* of other methods that can come into play in advanced usages, as
32	<	* well as extension mechanics that allow support of new forms of
33	<	* fork/join processing.
28	>	* programs using ForkJoinTasks employ only methods {@code fork} and
29	>	* {@code join}, or derivatives such as {@code invokeAll}.  However,
30	>	* this class also provides a number of other methods that can come
31	>	* into play in advanced usages, as well as extension mechanics that
32	>	* allow support of new forms of fork/join processing.
33		*
34		* <p>A ForkJoinTask is a lightweight form of {@link Future}.  The
35		* efficiency of ForkJoinTasks stems from a set of restrictions (that
#	Line 94 | Line 93 | import java.util.WeakHashMap;
93		* lightweight task scheduling framework, and so cannot be overridden.
94		* Developers creating new basic styles of fork/join processing should
95		* minimally implement {@code protected} methods
96	<	* {@code exec}, {@code setRawResult}, and
97	<	* {@code getRawResult}, while also introducing an abstract
96	>	* {@link #exec}, {@link #setRawResult}, and
97	>	* {@link #getRawResult}, while also introducing an abstract
98		* computational method that can be implemented in its subclasses,
99		* possibly relying on other {@code protected} methods provided
100		* by this class.
#	Line 248 | Line 247 | public abstract class ForkJoinTask<V> im
247		synchronized (this) {
248		try {
249		while (status >= 0) {
250	<	long nt = nanos - System.nanoTime() - startTime;
250	>	long nt = nanos - (System.nanoTime() - startTime);
251		if (nt <= 0)
252		break;
253		wait(nt / 1000000, (int) (nt % 1000000));
#	Line 492 | Line 491 | public abstract class ForkJoinTask<V> im
491		* computations (as may be determined using method {@link
492		* #inForkJoinPool}). Attempts to invoke in other contexts result
493		* in exceptions or errors, possibly including ClassCastException.
494	+	*
495	+	* @return {@code this}, to simplify usage.
496		*/
497	<	public final void fork() {
497	>	public final ForkJoinTask<V> fork() {
498		((ForkJoinWorkerThread) Thread.currentThread())
499		.pushTask(this);
500	+	return this;
501		}
502
503		/**
#	Line 603 | Line 605 | public abstract class ForkJoinTask<V> im
605		* in exceptions or errors, possibly including ClassCastException.
606		*
607		* @param tasks the collection of tasks
608	+	* @return the tasks argument, to simplify usage
609		* @throws NullPointerException if tasks or any element are null
610		* @throws RuntimeException or Error if any task did so
611		*/
612	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
612	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
613		if (!(tasks instanceof List<?>)) {
614		invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
615	<	return;
615	>	return tasks;
616		}
617		@SuppressWarnings("unchecked")
618		List<? extends ForkJoinTask<?>> ts =
#	Line 644 | Line 647 | public abstract class ForkJoinTask<V> im
647		}
648		if (ex != null)
649		rethrowException(ex);
650	+	return tasks;
651		}
652
653		/**
654	<	* Returns true if the computation performed by this task has
655	<	* completed (or has been cancelled).
654	>	* Returns {@code true} if the computation performed by this task
655	>	* has completed (or has been cancelled).
656		*
657	<	* @return true if this computation has completed
657	>	* @return {@code true} if this computation has completed
658		*/
659		public final boolean isDone() {
660		return status < 0;
661		}
662
663		/**
664	<	* Returns true if this task was cancelled.
664	>	* Returns {@code true} if this task was cancelled.
665		*
666	<	* @return true if this task was cancelled
666	>	* @return {@code true} if this task was cancelled
667		*/
668		public final boolean isCancelled() {
669		return (status & COMPLETION_MASK) == CANCELLED;
#	Line 668 | Line 672 | public abstract class ForkJoinTask<V> im
672		/**
673		* Asserts that the results of this task's computation will not be
674		* used. If a cancellation occurs before attempting to execute this
675	<	* task, then execution will be suppressed, {@code isCancelled}
676	<	* will report true, and {@code join} will result in a
675	>	* task, execution will be suppressed, {@link #isCancelled}
676	>	* will report true, and {@link #join} will result in a
677		* {@code CancellationException} being thrown. Otherwise, when
678		* cancellation races with completion, there are no guarantees
679	<	* about whether {@code isCancelled} will report true, whether
680	<	* {@code join} will return normally or via an exception, or
681	<	* whether these behaviors will remain consistent upon repeated
679	>	* about whether {@code isCancelled} will report {@code true},
680	>	* whether {@code join} will return normally or via an exception,
681	>	* or whether these behaviors will remain consistent upon repeated
682		* invocation.
683		*
684		* <p>This method may be overridden in subclasses, but if so, must
#	Line 684 | Line 688 | public abstract class ForkJoinTask<V> im
688		* <p> This method is designed to be invoked by <em>other</em>
689		* tasks. To terminate the current task, you can just return or
690		* throw an unchecked exception from its computation method, or
691	<	* invoke {@code completeExceptionally}.
691	>	* invoke {@link #completeExceptionally}.
692		*
693		* @param mayInterruptIfRunning this value is ignored in the
694		* default implementation because tasks are not in general
695		* cancelled via interruption
696		*
697	<	* @return true if this task is now cancelled
697	>	* @return {@code true} if this task is now cancelled
698		*/
699		public boolean cancel(boolean mayInterruptIfRunning) {
700		setCompletion(CANCELLED);
#	Line 698 | Line 702 | public abstract class ForkJoinTask<V> im
702		}
703
704		/**
705	<	* Returns true if this task threw an exception or was cancelled.
705	>	* Returns {@code true} if this task threw an exception or was cancelled.
706		*
707	<	* @return true if this task threw an exception or was cancelled
707	>	* @return {@code true} if this task threw an exception or was cancelled
708		*/
709		public final boolean isCompletedAbnormally() {
710		return (status & COMPLETION_MASK) < NORMAL;
#	Line 711 | Line 715 | public abstract class ForkJoinTask<V> im
715		* CancellationException if cancelled, or null if none or if the
716		* method has not yet completed.
717		*
718	<	* @return the exception, or null if none
718	>	* @return the exception, or {@code null} if none
719		*/
720		public final Throwable getException() {
721		int s = status & COMPLETION_MASK;
#	Line 773 | Line 777 | public abstract class ForkJoinTask<V> im
777
778		public final V get(long timeout, TimeUnit unit)
779		throws InterruptedException, ExecutionException, TimeoutException {
780	+	long nanos = unit.toNanos(timeout);
781		ForkJoinWorkerThread w = getWorker();
782		if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
783	<	awaitDone(w, unit.toNanos(timeout));
783	>	awaitDone(w, nanos);
784		return reportTimedFutureResult();
785		}
786
#	Line 874 | Line 879 | public abstract class ForkJoinTask<V> im
879		* Returns the pool hosting the current task execution, or null
880		* if this task is executing outside of any ForkJoinPool.
881		*
882	<	* @return the pool, or null if none
882	>	* @return the pool, or {@code null} if none
883		*/
884		public static ForkJoinPool getPool() {
885		Thread t = Thread.currentThread();
#	Line 905 | Line 910 | public abstract class ForkJoinTask<V> im
910		* result in exceptions or errors, possibly including
911		* ClassCastException.
912		*
913	<	* @return true if unforked
913	>	* @return {@code true} if unforked
914		*/
915		public boolean tryUnfork() {
916		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 945 | Line 950 | public abstract class ForkJoinTask<V> im
950		// Extension methods
951
952		/**
953	<	* Returns the result that would be returned by {@code join},
954	<	* even if this task completed abnormally, or null if this task is
955	<	* not known to have been completed.  This method is designed to
956	<	* aid debugging, as well as to support extensions. Its use in any
957	<	* other context is discouraged.
953	>	* Returns the result that would be returned by {@link #join}, even
954	>	* if this task completed abnormally, or {@code null} if this task
955	>	* is not known to have been completed.  This method is designed
956	>	* to aid debugging, as well as to support extensions. Its use in
957	>	* any other context is discouraged.
958		*
959	<	* @return the result, or null if not completed
959	>	* @return the result, or {@code null} if not completed
960		*/
961		public abstract V getRawResult();
962
#	Line 970 | Line 975 | public abstract class ForkJoinTask<V> im
975		* called otherwise. The return value controls whether this task
976		* is considered to be done normally. It may return false in
977		* asynchronous actions that require explicit invocations of
978	<	* {@code complete} to become joinable. It may throw exceptions
978	>	* {@link #complete} to become joinable. It may throw exceptions
979		* to indicate abnormal exit.
980		*
981	<	* @return true if completed normally
981	>	* @return {@code true} if completed normally
982		* @throws Error or RuntimeException if encountered during computation
983		*/
984		protected abstract boolean exec();
985
986		/**
987	<	* Returns, but does not unschedule or execute, the task queued by
988	<	* the current thread but not yet executed, if one is
987	>	* Returns, but does not unschedule or execute, a task queued by
988	>	* the current thread but not yet executed, if one is immediately
989		* available. There is no guarantee that this task will actually
990	<	* be polled or executed next.  This method is designed primarily
991	<	* to support extensions, and is unlikely to be useful otherwise.
992	<	* This method may be invoked only from within ForkJoinTask
993	<	* computations (as may be determined using method {@link
994	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
995	<	* in exceptions or errors, possibly including ClassCastException.
990	>	* be polled or executed next. Conversely, this method may return
991	>	* null even if a task exists but cannot be accessed without
992	>	* contention with other threads.  This method is designed
993	>	* primarily to support extensions, and is unlikely to be useful
994	>	* otherwise.  This method may be invoked only from within
995	>	* ForkJoinTask computations (as may be determined using method
996	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
997	>	* result in exceptions or errors, possibly including
998	>	* ClassCastException.
999		*
1000	<	* @return the next task, or null if none are available
1000	>	* @return the next task, or {@code null} if none are available
1001		*/
1002		protected static ForkJoinTask<?> peekNextLocalTask() {
1003		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 1006 | Line 1014 | public abstract class ForkJoinTask<V> im
1014		* contexts result in exceptions or errors, possibly including
1015		* ClassCastException.
1016		*
1017	<	* @return the next task, or null if none are available
1017	>	* @return the next task, or {@code null} if none are available
1018		*/
1019		protected static ForkJoinTask<?> pollNextLocalTask() {
1020		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 1027 | Line 1035 | public abstract class ForkJoinTask<V> im
1035		* result in exceptions or errors, possibly including
1036		* ClassCastException.
1037		*
1038	<	* @return a task, or null if none are available
1038	>	* @return a task, or {@code null} if none are available
1039		*/
1040		protected static ForkJoinTask<?> pollTask() {
1041		return ((ForkJoinWorkerThread) Thread.currentThread())
1042		.pollTask();
1043		}
1044
1045	+	/**
1046	+	* Adaptor for Runnables. This implements RunnableFuture
1047	+	* to be compliant with AbstractExecutorService constraints
1048	+	* when used in ForkJoinPool.
1049	+	*/
1050	+	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1051	+	implements RunnableFuture<T> {
1052	+	final Runnable runnable;
1053	+	final T resultOnCompletion;
1054	+	T result;
1055	+	AdaptedRunnable(Runnable runnable, T result) {
1056	+	if (runnable == null) throw new NullPointerException();
1057	+	this.runnable = runnable;
1058	+	this.resultOnCompletion = result;
1059	+	}
1060	+	public T getRawResult() { return result; }
1061	+	public void setRawResult(T v) { result = v; }
1062	+	public boolean exec() {
1063	+	runnable.run();
1064	+	result = resultOnCompletion;
1065	+	return true;
1066	+	}
1067	+	public void run() { invoke(); }
1068	+	private static final long serialVersionUID = 5232453952276885070L;
1069	+	}
1070	+
1071	+	/**
1072	+	* Adaptor for Callables
1073	+	*/
1074	+	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1075	+	implements RunnableFuture<T> {
1076	+	final Callable<T> callable;
1077	+	T result;
1078	+	AdaptedCallable(Callable<T> callable) {
1079	+	if (callable == null) throw new NullPointerException();
1080	+	this.callable = callable;
1081	+	}
1082	+	public T getRawResult() { return result; }
1083	+	public void setRawResult(T v) { result = v; }
1084	+	public boolean exec() {
1085	+	try {
1086	+	result = callable.call();
1087	+	return true;
1088	+	} catch (Error err) {
1089	+	throw err;
1090	+	} catch (RuntimeException rex) {
1091	+	throw rex;
1092	+	} catch (Exception ex) {
1093	+	throw new RuntimeException(ex);
1094	+	}
1095	+	}
1096	+	public void run() { invoke(); }
1097	+	private static final long serialVersionUID = 2838392045355241008L;
1098	+	}
1099	+
1100	+	/**
1101	+	* Returns a new ForkJoinTask that performs the {@code run}
1102	+	* method of the given Runnable as its action, and returns a null
1103	+	* result upon {@code join}.
1104	+	*
1105	+	* @param runnable the runnable action
1106	+	* @return the task
1107	+	*/
1108	+	public static ForkJoinTask<Void> adapt(Runnable runnable) {
1109	+	return new AdaptedRunnable<Void>(runnable, null);
1110	+	}
1111	+
1112	+	/**
1113	+	* Returns a new ForkJoinTask that performs the {@code run}
1114	+	* method of the given Runnable as its action, and returns the
1115	+	* given result upon {@code join}.
1116	+	*
1117	+	* @param runnable the runnable action
1118	+	* @param result the result upon completion
1119	+	* @return the task
1120	+	*/
1121	+	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1122	+	return new AdaptedRunnable<T>(runnable, result);
1123	+	}
1124	+
1125	+	/**
1126	+	* Returns a new ForkJoinTask that performs the {@code call}
1127	+	* method of the given Callable as its action, and returns its
1128	+	* result upon {@code join}, translating any checked
1129	+	* exceptions encountered into {@code RuntimeException}.
1130	+	*
1131	+	* @param callable the callable action
1132	+	* @return the task
1133	+	*/
1134	+	public static <T> ForkJoinTask<T> adapt(Callable<T> callable) {
1135	+	return new AdaptedCallable<T>(callable);
1136	+	}
1137	+
1138		// Serialization support
1139
1140		private static final long serialVersionUID = -7721805057305804111L;
#	Line 1042 | Line 1143 | public abstract class ForkJoinTask<V> im
1143		* Save the state to a stream.
1144		*
1145		* @serialData the current run status and the exception thrown
1146	<	* during execution, or null if none
1146	>	* during execution, or {@code null} if none
1147		* @param s the stream
1148		*/
1149		private void writeObject(java.io.ObjectOutputStream s)
#	Line 1066 | Line 1167 | public abstract class ForkJoinTask<V> im
1167		setDoneExceptionally((Throwable) ex);
1168		}
1169
1170	<	// Unsafe mechanics for jsr166y 3rd party package.
1170	>	// Unsafe mechanics
1171	>
1172	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1173	>	private static final long statusOffset =
1174	>	objectFieldOffset("status", ForkJoinTask.class);
1175	>
1176	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1177	>	try {
1178	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1179	>	} catch (NoSuchFieldException e) {
1180	>	// Convert Exception to corresponding Error
1181	>	NoSuchFieldError error = new NoSuchFieldError(field);
1182	>	error.initCause(e);
1183	>	throw error;
1184	>	}
1185	>	}
1186	>
1187	>	/**
1188	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1189	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1190	>	* into a jdk.
1191	>	*
1192	>	* @return a sun.misc.Unsafe
1193	>	*/
1194		private static sun.misc.Unsafe getUnsafe() {
1195		try {
1196		return sun.misc.Unsafe.getUnsafe();
1197		} catch (SecurityException se) {
1198		try {
1199		return java.security.AccessController.doPrivileged
1200	<	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1200	>	(new java.security
1201	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1202		public sun.misc.Unsafe run() throws Exception {
1203	<	return getUnsafeByReflection();
1203	>	java.lang.reflect.Field f = sun.misc
1204	>	.Unsafe.class.getDeclaredField("theUnsafe");
1205	>	f.setAccessible(true);
1206	>	return (sun.misc.Unsafe) f.get(null);
1207		}});
1208		} catch (java.security.PrivilegedActionException e) {
1209		throw new RuntimeException("Could not initialize intrinsics",
#	Line 1083 | Line 1211 | public abstract class ForkJoinTask<V> im
1211		}
1212		}
1213		}
1086	–
1087	–	private static sun.misc.Unsafe getUnsafeByReflection()
1088	–	throws NoSuchFieldException, IllegalAccessException {
1089	–	java.lang.reflect.Field f =
1090	–	sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
1091	–	f.setAccessible(true);
1092	–	return (sun.misc.Unsafe) f.get(null);
1093	–	}
1094	–
1095	–	private static long fieldOffset(String fieldName, Class<?> klazz) {
1096	–	try {
1097	–	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName));
1098	–	} catch (NoSuchFieldException e) {
1099	–	// Convert Exception to Error
1100	–	NoSuchFieldError error = new NoSuchFieldError(fieldName);
1101	–	error.initCause(e);
1102	–	throw error;
1103	–	}
1104	–	}
1105	–
1106	–	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1107	–	static final long statusOffset =
1108	–	fieldOffset("status", ForkJoinTask.class);
1109	–
1214		}

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