--- jsr166/src/jsr166y/ForkJoinTask.java 2009/07/26 06:26:37 1.21
+++ jsr166/src/jsr166y/ForkJoinTask.java 2009/07/27 21:41:53 1.24
@@ -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.
@@ -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;
@@ -879,7 +878,7 @@ 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 +909,7 @@ 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 +949,13 @@ 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();
@@ -975,10 +974,10 @@ 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();
@@ -994,7 +993,7 @@ public abstract class ForkJoinTask im
* #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 +1010,7 @@ 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())
@@ -1032,7 +1031,7 @@ 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())
@@ -1087,7 +1086,7 @@ 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)
@@ -1111,16 +1110,43 @@ public abstract class ForkJoinTask im
setDoneExceptionally((Throwable) ex);
}
- // Unsafe mechanics for jsr166y 3rd party package.
+ // Unsafe mechanics
+
+ private static final sun.misc.Unsafe UNSAFE = getUnsafe();
+ private static final long statusOffset =
+ objectFieldOffset("status", ForkJoinTask.class);
+
+ private static long objectFieldOffset(String field, Class klazz) {
+ try {
+ return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
+ } catch (NoSuchFieldException e) {
+ // Convert Exception to corresponding Error
+ NoSuchFieldError error = new NoSuchFieldError(field);
+ error.initCause(e);
+ throw error;
+ }
+ }
+
+ /**
+ * Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package.
+ * Replace with a simple call to Unsafe.getUnsafe when integrating
+ * into a jdk.
+ *
+ * @return a sun.misc.Unsafe
+ */
private static sun.misc.Unsafe getUnsafe() {
try {
return sun.misc.Unsafe.getUnsafe();
} catch (SecurityException se) {
try {
return java.security.AccessController.doPrivileged
- (new java.security.PrivilegedExceptionAction() {
+ (new java.security
+ .PrivilegedExceptionAction() {
public sun.misc.Unsafe run() throws Exception {
- return getUnsafeByReflection();
+ java.lang.reflect.Field f = sun.misc
+ .Unsafe.class.getDeclaredField("theUnsafe");
+ f.setAccessible(true);
+ return (sun.misc.Unsafe) f.get(null);
}});
} catch (java.security.PrivilegedActionException e) {
throw new RuntimeException("Could not initialize intrinsics",
@@ -1128,28 +1154,4 @@ public abstract class ForkJoinTask im
}
}
}
-
- private static sun.misc.Unsafe getUnsafeByReflection()
- throws NoSuchFieldException, IllegalAccessException {
- java.lang.reflect.Field f =
- sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
- f.setAccessible(true);
- return (sun.misc.Unsafe) f.get(null);
- }
-
- private static long fieldOffset(String fieldName, Class klazz) {
- try {
- return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName));
- } catch (NoSuchFieldException e) {
- // Convert Exception to Error
- NoSuchFieldError error = new NoSuchFieldError(fieldName);
- error.initCause(e);
- throw error;
- }
- }
-
- private static final sun.misc.Unsafe UNSAFE = getUnsafe();
- private static final long statusOffset =
- fieldOffset("status", ForkJoinTask.class);
-
}