--- jsr166/src/jsr166y/ForkJoinTask.java 2009/07/26 17:33:37 1.22
+++ jsr166/src/jsr166y/ForkJoinTask.java 2009/08/01 21:17:11 1.26
@@ -16,8 +16,8 @@ import java.util.Map;
import java.util.WeakHashMap;
/**
- * Abstract base class for tasks that run within a {@link
- * ForkJoinPool}. A ForkJoinTask is a thread-like entity that is much
+ * Abstract base class for tasks that run within a {@link ForkJoinPool}.
+ * A {@code ForkJoinTask} is a thread-like entity that is much
* lighter weight than a normal thread. Huge numbers of tasks and
* subtasks may be hosted by a small number of actual threads in a
* ForkJoinPool, at the price of some usage limitations.
@@ -25,12 +25,11 @@ import java.util.WeakHashMap;
*
A "main" ForkJoinTask begins execution when submitted to a
* {@link ForkJoinPool}. Once started, it will usually in turn start
* other subtasks. As indicated by the name of this class, many
- * programs using ForkJoinTasks employ only methods {@code fork}
- * and {@code join}, or derivatives such as
- * {@code invokeAll}. However, this class also provides a number
- * of other methods that can come into play in advanced usages, as
- * well as extension mechanics that allow support of new forms of
- * fork/join processing.
+ * programs using ForkJoinTasks employ only methods {@code fork} and
+ * {@code join}, or derivatives such as {@code invokeAll}. However,
+ * this class also provides a number of other methods that can come
+ * into play in advanced usages, as well as extension mechanics that
+ * allow support of new forms of fork/join processing.
*
*
A ForkJoinTask is a lightweight form of {@link Future}. The
* efficiency of ForkJoinTasks stems from a set of restrictions (that
@@ -94,8 +93,8 @@ import java.util.WeakHashMap;
* lightweight task scheduling framework, and so cannot be overridden.
* Developers creating new basic styles of fork/join processing should
* minimally implement {@code protected} methods
- * {@code exec}, {@code setRawResult}, and
- * {@code getRawResult}, while also introducing an abstract
+ * {@link #exec}, {@link #setRawResult}, and
+ * {@link #getRawResult}, while also introducing an abstract
* computational method that can be implemented in its subclasses,
* possibly relying on other {@code protected} methods provided
* by this class.
@@ -248,7 +247,7 @@ public abstract class ForkJoinTask im
synchronized (this) {
try {
while (status >= 0) {
- long nt = nanos - System.nanoTime() - startTime;
+ long nt = nanos - (System.nanoTime() - startTime);
if (nt <= 0)
break;
wait(nt / 1000000, (int) (nt % 1000000));
@@ -652,19 +651,19 @@ public abstract class ForkJoinTask im
}
/**
- * Returns true if the computation performed by this task has
- * completed (or has been cancelled).
+ * Returns {@code true} if the computation performed by this task
+ * has completed (or has been cancelled).
*
- * @return true if this computation has completed
+ * @return {@code true} if this computation has completed
*/
public final boolean isDone() {
return status < 0;
}
/**
- * Returns true if this task was cancelled.
+ * Returns {@code true} if this task was cancelled.
*
- * @return true if this task was cancelled
+ * @return {@code true} if this task was cancelled
*/
public final boolean isCancelled() {
return (status & COMPLETION_MASK) == CANCELLED;
@@ -673,13 +672,13 @@ public abstract class ForkJoinTask im
/**
* Asserts that the results of this task's computation will not be
* used. If a cancellation occurs before attempting to execute this
- * task, then execution will be suppressed, {@code isCancelled}
- * will report true, and {@code join} will result in a
+ * task, execution will be suppressed, {@link #isCancelled}
+ * will report true, and {@link #join} will result in a
* {@code CancellationException} being thrown. Otherwise, when
* cancellation races with completion, there are no guarantees
- * about whether {@code isCancelled} will report true, whether
- * {@code join} will return normally or via an exception, or
- * whether these behaviors will remain consistent upon repeated
+ * about whether {@code isCancelled} will report {@code true},
+ * whether {@code join} will return normally or via an exception,
+ * or whether these behaviors will remain consistent upon repeated
* invocation.
*
* This method may be overridden in subclasses, but if so, must
@@ -689,13 +688,13 @@ public abstract class ForkJoinTask im
* This method is designed to be invoked by other
* tasks. To terminate the current task, you can just return or
* throw an unchecked exception from its computation method, or
- * invoke {@code completeExceptionally}.
+ * invoke {@link #completeExceptionally}.
*
* @param mayInterruptIfRunning this value is ignored in the
* default implementation because tasks are not in general
* cancelled via interruption
*
- * @return true if this task is now cancelled
+ * @return {@code true} if this task is now cancelled
*/
public boolean cancel(boolean mayInterruptIfRunning) {
setCompletion(CANCELLED);
@@ -703,9 +702,9 @@ public abstract class ForkJoinTask im
}
/**
- * Returns true if this task threw an exception or was cancelled.
+ * Returns {@code true} if this task threw an exception or was cancelled.
*
- * @return true if this task threw an exception or was cancelled
+ * @return {@code true} if this task threw an exception or was cancelled
*/
public final boolean isCompletedAbnormally() {
return (status & COMPLETION_MASK) < NORMAL;
@@ -716,7 +715,7 @@ public abstract class ForkJoinTask im
* CancellationException if cancelled, or null if none or if the
* method has not yet completed.
*
- * @return the exception, or null if none
+ * @return the exception, or {@code null} if none
*/
public final Throwable getException() {
int s = status & COMPLETION_MASK;
@@ -778,9 +777,10 @@ public abstract class ForkJoinTask im
public final V get(long timeout, TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException {
+ long nanos = unit.toNanos(timeout);
ForkJoinWorkerThread w = getWorker();
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
- awaitDone(w, unit.toNanos(timeout));
+ awaitDone(w, nanos);
return reportTimedFutureResult();
}
@@ -879,7 +879,7 @@ public abstract class ForkJoinTask im
* Returns the pool hosting the current task execution, or null
* if this task is executing outside of any ForkJoinPool.
*
- * @return the pool, or null if none
+ * @return the pool, or {@code null} if none
*/
public static ForkJoinPool getPool() {
Thread t = Thread.currentThread();
@@ -910,7 +910,7 @@ public abstract class ForkJoinTask im
* result in exceptions or errors, possibly including
* ClassCastException.
*
- * @return true if unforked
+ * @return {@code true} if unforked
*/
public boolean tryUnfork() {
return ((ForkJoinWorkerThread) Thread.currentThread())
@@ -950,13 +950,13 @@ public abstract class ForkJoinTask im
// Extension methods
/**
- * Returns the result that would be returned by {@code join},
- * even if this task completed abnormally, or null if this task is
- * not known to have been completed. This method is designed to
- * aid debugging, as well as to support extensions. Its use in any
- * other context is discouraged.
+ * Returns the result that would be returned by {@link #join}, even
+ * if this task completed abnormally, or {@code null} if this task
+ * is not known to have been completed. This method is designed
+ * to aid debugging, as well as to support extensions. Its use in
+ * any other context is discouraged.
*
- * @return the result, or null if not completed
+ * @return the result, or {@code null} if not completed
*/
public abstract V getRawResult();
@@ -975,26 +975,29 @@ public abstract class ForkJoinTask im
* called otherwise. The return value controls whether this task
* is considered to be done normally. It may return false in
* asynchronous actions that require explicit invocations of
- * {@code complete} to become joinable. It may throw exceptions
+ * {@link #complete} to become joinable. It may throw exceptions
* to indicate abnormal exit.
*
- * @return true if completed normally
+ * @return {@code true} if completed normally
* @throws Error or RuntimeException if encountered during computation
*/
protected abstract boolean exec();
/**
- * Returns, but does not unschedule or execute, the task queued by
- * the current thread but not yet executed, if one is
+ * Returns, but does not unschedule or execute, a task queued by
+ * the current thread but not yet executed, if one is immediately
* available. There is no guarantee that this task will actually
- * be polled or executed next. This method is designed primarily
- * to support extensions, and is unlikely to be useful otherwise.
- * This method may be invoked only from within ForkJoinTask
- * computations (as may be determined using method {@link
- * #inForkJoinPool}). Attempts to invoke in other contexts result
- * in exceptions or errors, possibly including ClassCastException.
+ * be polled or executed next. Conversely, this method may return
+ * null even if a task exists but cannot be accessed without
+ * contention with other threads. This method is designed
+ * primarily to support extensions, and is unlikely to be useful
+ * otherwise. This method may be invoked only from within
+ * ForkJoinTask computations (as may be determined using method
+ * {@link #inForkJoinPool}). Attempts to invoke in other contexts
+ * result in exceptions or errors, possibly including
+ * ClassCastException.
*
- * @return the next task, or null if none are available
+ * @return the next task, or {@code null} if none are available
*/
protected static ForkJoinTask> peekNextLocalTask() {
return ((ForkJoinWorkerThread) Thread.currentThread())
@@ -1011,7 +1014,7 @@ public abstract class ForkJoinTask im
* contexts result in exceptions or errors, possibly including
* ClassCastException.
*
- * @return the next task, or null if none are available
+ * @return the next task, or {@code null} if none are available
*/
protected static ForkJoinTask> pollNextLocalTask() {
return ((ForkJoinWorkerThread) Thread.currentThread())
@@ -1032,14 +1035,67 @@ public abstract class ForkJoinTask im
* result in exceptions or errors, possibly including
* ClassCastException.
*
- * @return a task, or null if none are available
+ * @return a task, or {@code null} if none are available
*/
protected static ForkJoinTask> pollTask() {
return ((ForkJoinWorkerThread) Thread.currentThread())
.pollTask();
}
- // adaptors
+ /**
+ * Adaptor for Runnables. This implements RunnableFuture
+ * to be compliant with AbstractExecutorService constraints
+ * when used in ForkJoinPool.
+ */
+ static final class AdaptedRunnable extends ForkJoinTask
+ implements RunnableFuture {
+ final Runnable runnable;
+ final T resultOnCompletion;
+ T result;
+ AdaptedRunnable(Runnable runnable, T result) {
+ if (runnable == null) throw new NullPointerException();
+ this.runnable = runnable;
+ this.resultOnCompletion = result;
+ }
+ public T getRawResult() { return result; }
+ public void setRawResult(T v) { result = v; }
+ public boolean exec() {
+ runnable.run();
+ result = resultOnCompletion;
+ return true;
+ }
+ public void run() { invoke(); }
+ private static final long serialVersionUID = 5232453952276885070L;
+ }
+
+ /**
+ * Adaptor for Callables
+ */
+ static final class AdaptedCallable extends ForkJoinTask
+ implements RunnableFuture {
+ final Callable callable;
+ T result;
+ AdaptedCallable(Callable callable) {
+ if (callable == null) throw new NullPointerException();
+ this.callable = callable;
+ }
+ public T getRawResult() { return result; }
+ public void setRawResult(T v) { result = v; }
+ public boolean exec() {
+ try {
+ result = callable.call();
+ return true;
+ } catch (Error err) {
+ throw err;
+ } catch (RuntimeException rex) {
+ throw rex;
+ } catch (Exception ex) {
+ throw new RuntimeException(ex);
+ }
+ }
+ public void run() { invoke(); }
+ private static final long serialVersionUID = 2838392045355241008L;
+ }
/**
* Returns a new ForkJoinTask that performs the {@code run}
@@ -1050,7 +1106,7 @@ public abstract class ForkJoinTask im
* @return the task
*/
public static ForkJoinTask adapt(Runnable runnable) {
- return new ForkJoinPool.AdaptedRunnable(runnable, null);
+ return new AdaptedRunnable(runnable, null);
}
/**
@@ -1063,7 +1119,7 @@ public abstract class ForkJoinTask im
* @return the task
*/
public static ForkJoinTask adapt(Runnable runnable, T result) {
- return new ForkJoinPool.AdaptedRunnable(runnable, result);
+ return new AdaptedRunnable(runnable, result);
}
/**
@@ -1076,7 +1132,7 @@ public abstract class ForkJoinTask im
* @return the task
*/
public static ForkJoinTask adapt(Callable callable) {
- return new ForkJoinPool.AdaptedCallable(callable);
+ return new AdaptedCallable(callable);
}
// Serialization support
@@ -1087,7 +1143,7 @@ public abstract class ForkJoinTask im
* Save the state to a stream.
*
* @serialData the current run status and the exception thrown
- * during execution, or null if none
+ * during execution, or {@code null} if none
* @param s the stream
*/
private void writeObject(java.io.ObjectOutputStream s)