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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.18 by dl, Sat Jul 25 15:50:57 2009 UTC vs.
Revision 1.24 by jsr166, Mon Jul 27 21:41:53 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 493 | Line 492 | public abstract class ForkJoinTask<V> im
492		* #inForkJoinPool}). Attempts to invoke in other contexts result
493		* in exceptions or errors, possibly including ClassCastException.
494		*
495	<	* @return <code>this</code>, to simplify usage.
495	>	* @return {@code this}, to simplify usage.
496		*/
497		public final ForkJoinTask<V> fork() {
498		((ForkJoinWorkerThread) Thread.currentThread())
#	Line 606 | 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 647 | 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 671 | 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 687 | 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 701 | 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 714 | 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 877 | Line 878 | public abstract class ForkJoinTask<V> im
878		* Returns the pool hosting the current task execution, or null
879		* if this task is executing outside of any ForkJoinPool.
880		*
881	<	* @return the pool, or null if none
881	>	* @return the pool, or {@code null} if none
882		*/
883		public static ForkJoinPool getPool() {
884		Thread t = Thread.currentThread();
#	Line 908 | Line 909 | public abstract class ForkJoinTask<V> im
909		* result in exceptions or errors, possibly including
910		* ClassCastException.
911		*
912	<	* @return true if unforked
912	>	* @return {@code true} if unforked
913		*/
914		public boolean tryUnfork() {
915		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 948 | Line 949 | public abstract class ForkJoinTask<V> im
949		// Extension methods
950
951		/**
952	<	* Returns the result that would be returned by {@code join},
953	<	* even if this task completed abnormally, or null if this task is
954	<	* not known to have been completed.  This method is designed to
955	<	* aid debugging, as well as to support extensions. Its use in any
956	<	* other context is discouraged.
952	>	* Returns the result that would be returned by {@link #join}, even
953	>	* if this task completed abnormally, or {@code null} if this task
954	>	* is not known to have been completed.  This method is designed
955	>	* to aid debugging, as well as to support extensions. Its use in
956	>	* any other context is discouraged.
957		*
958	<	* @return the result, or null if not completed
958	>	* @return the result, or {@code null} if not completed
959		*/
960		public abstract V getRawResult();
961
#	Line 973 | Line 974 | public abstract class ForkJoinTask<V> im
974		* called otherwise. The return value controls whether this task
975		* is considered to be done normally. It may return false in
976		* asynchronous actions that require explicit invocations of
977	<	* {@code complete} to become joinable. It may throw exceptions
977	>	* {@link #complete} to become joinable. It may throw exceptions
978		* to indicate abnormal exit.
979		*
980	<	* @return true if completed normally
980	>	* @return {@code true} if completed normally
981		* @throws Error or RuntimeException if encountered during computation
982		*/
983		protected abstract boolean exec();
#	Line 992 | Line 993 | public abstract class ForkJoinTask<V> im
993		* #inForkJoinPool}). Attempts to invoke in other contexts result
994		* in exceptions or errors, possibly including ClassCastException.
995		*
996	<	* @return the next task, or null if none are available
996	>	* @return the next task, or {@code null} if none are available
997		*/
998		protected static ForkJoinTask<?> peekNextLocalTask() {
999		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 1009 | Line 1010 | public abstract class ForkJoinTask<V> im
1010		* contexts result in exceptions or errors, possibly including
1011		* ClassCastException.
1012		*
1013	<	* @return the next task, or null if none are available
1013	>	* @return the next task, or {@code null} if none are available
1014		*/
1015		protected static ForkJoinTask<?> pollNextLocalTask() {
1016		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 1030 | Line 1031 | public abstract class ForkJoinTask<V> im
1031		* result in exceptions or errors, possibly including
1032		* ClassCastException.
1033		*
1034	<	* @return a task, or null if none are available
1034	>	* @return a task, or {@code null} if none are available
1035		*/
1036		protected static ForkJoinTask<?> pollTask() {
1037		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 1040 | Line 1041 | public abstract class ForkJoinTask<V> im
1041		// adaptors
1042
1043		/**
1044	<	* Returns a new ForkJoinTask that performs the <code>run</code>
1044	>	* Returns a new ForkJoinTask that performs the {@code run}
1045		* method of the given Runnable as its action, and returns a null
1046	<	* result upon <code>join</code>.
1046	>	* result upon {@code join}.
1047		*
1048		* @param runnable the runnable action
1049		* @return the task
#	Line 1052 | Line 1053 | public abstract class ForkJoinTask<V> im
1053		}
1054
1055		/**
1056	<	* Returns a new ForkJoinTask that performs the <code>run</code>
1056	>	* Returns a new ForkJoinTask that performs the {@code run}
1057		* method of the given Runnable as its action, and returns the
1058	<	* given result upon <code>join</code>.
1058	>	* given result upon {@code join}.
1059		*
1060		* @param runnable the runnable action
1061		* @param result the result upon completion
#	Line 1065 | Line 1066 | public abstract class ForkJoinTask<V> im
1066		}
1067
1068		/**
1069	<	* Returns a new ForkJoinTask that performs the <code>call</code>
1069	>	* Returns a new ForkJoinTask that performs the {@code call}
1070		* method of the given Callable as its action, and returns its
1071	<	* result upon <code>join</code>, translating any checked
1072	<	* exceptions encountered into <code>RuntimeException<code>.
1071	>	* result upon {@code join}, translating any checked
1072	>	* exceptions encountered into {@code RuntimeException}.
1073		*
1074		* @param callable the callable action
1075		* @return the task
#	Line 1085 | Line 1086 | public abstract class ForkJoinTask<V> im
1086		* Save the state to a stream.
1087		*
1088		* @serialData the current run status and the exception thrown
1089	<	* during execution, or null if none
1089	>	* during execution, or {@code null} if none
1090		* @param s the stream
1091		*/
1092		private void writeObject(java.io.ObjectOutputStream s)
#	Line 1109 | Line 1110 | public abstract class ForkJoinTask<V> im
1110		setDoneExceptionally((Throwable) ex);
1111		}
1112
1113	<	// Unsafe mechanics for jsr166y 3rd party package.
1113	>	// Unsafe mechanics
1114	>
1115	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1116	>	private static final long statusOffset =
1117	>	objectFieldOffset("status", ForkJoinTask.class);
1118	>
1119	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1120	>	try {
1121	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1122	>	} catch (NoSuchFieldException e) {
1123	>	// Convert Exception to corresponding Error
1124	>	NoSuchFieldError error = new NoSuchFieldError(field);
1125	>	error.initCause(e);
1126	>	throw error;
1127	>	}
1128	>	}
1129	>
1130	>	/**
1131	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1132	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1133	>	* into a jdk.
1134	>	*
1135	>	* @return a sun.misc.Unsafe
1136	>	*/
1137		private static sun.misc.Unsafe getUnsafe() {
1138		try {
1139		return sun.misc.Unsafe.getUnsafe();
1140		} catch (SecurityException se) {
1141		try {
1142		return java.security.AccessController.doPrivileged
1143	<	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1143	>	(new java.security
1144	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1145		public sun.misc.Unsafe run() throws Exception {
1146	<	return getUnsafeByReflection();
1146	>	java.lang.reflect.Field f = sun.misc
1147	>	.Unsafe.class.getDeclaredField("theUnsafe");
1148	>	f.setAccessible(true);
1149	>	return (sun.misc.Unsafe) f.get(null);
1150		}});
1151		} catch (java.security.PrivilegedActionException e) {
1152		throw new RuntimeException("Could not initialize intrinsics",
#	Line 1126 | Line 1154 | public abstract class ForkJoinTask<V> im
1154		}
1155		}
1156		}
1129	–
1130	–	private static sun.misc.Unsafe getUnsafeByReflection()
1131	–	throws NoSuchFieldException, IllegalAccessException {
1132	–	java.lang.reflect.Field f =
1133	–	sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
1134	–	f.setAccessible(true);
1135	–	return (sun.misc.Unsafe) f.get(null);
1136	–	}
1137	–
1138	–	private static long fieldOffset(String fieldName, Class<?> klazz) {
1139	–	try {
1140	–	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName));
1141	–	} catch (NoSuchFieldException e) {
1142	–	// Convert Exception to Error
1143	–	NoSuchFieldError error = new NoSuchFieldError(fieldName);
1144	–	error.initCause(e);
1145	–	throw error;
1146	–	}
1147	–	}
1148	–
1149	–	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1150	–	static final long statusOffset =
1151	–	fieldOffset("status", ForkJoinTask.class);
1152	–
1157		}

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