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package jsr166y; |
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import java.util.concurrent.*; |
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import java.io.Serializable; |
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import java.util.Collection; |
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import java.util.Collections; |
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* start other subtasks. As indicated by the name of this class, |
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* many programs using {@code ForkJoinTask} employ only methods |
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* {@link #fork} and {@link #join}, or derivatives such as {@link |
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* #invokeAll}. However, this class also provides a number of other |
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* methods that can come into play in advanced usages, as well as |
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* extension mechanics that allow support of new forms of fork/join |
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* processing. |
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* #invokeAll(ForkJoinTask...) invokeAll}. However, this class also |
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* provides a number of other methods that can come into play in |
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* advanced usages, as well as extension mechanics that allow |
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* support of new forms of fork/join processing. |
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* |
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* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}. |
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* The efficiency of {@code ForkJoinTask}s stems from a set of |
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* ForkJoinTasks (as may be determined using method {@link |
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* #inForkJoinPool}). Attempts to invoke them in other contexts |
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* result in exceptions or errors, possibly including |
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* ClassCastException. |
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* {@code ClassCastException}. |
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* |
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* <p>Most base support methods are {@code final}, to prevent |
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* overriding of implementations that are intrinsically tied to the |
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* single int to minimize footprint and to ensure atomicity (via |
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* CAS). Status is initially zero, and takes on nonnegative |
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* values until completed, upon which status holds value |
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* COMPLETED. CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking |
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* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking |
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* waits by other threads have the SIGNAL bit set. Completion of |
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* a stolen task with SIGNAL set awakens any waiters via |
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* notifyAll. Even though suboptimal for some purposes, we use |
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} |
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/** |
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* Record exception and set exceptional completion |
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* Records exception and sets exceptional completion. |
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* |
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* @return status on exit |
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*/ |
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private void setExceptionalCompletion(Throwable rex) { |
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} |
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/** |
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* Blocks a worker thread until completion. Called only by pool. |
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* Blocks a worker thread until completion. Called only by |
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* pool. Currently unused -- pool-based waits use timeout |
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* version below. |
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*/ |
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final void internalAwaitDone() { |
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int s; // the odd construction reduces lock bias effects |
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while ((s = status) >= 0) { |
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try { |
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synchronized(this) { |
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synchronized (this) { |
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if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL)) |
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wait(); |
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} |
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} |
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/** |
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* Blocks a worker thread until completed or timed out. Called |
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* only by pool. |
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* |
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* @return status on exit |
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*/ |
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final int internalAwaitDone(long millis) { |
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int s; |
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if ((s = status) >= 0) { |
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try { |
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synchronized (this) { |
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if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL)) |
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wait(millis, 0); |
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} |
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} catch (InterruptedException ie) { |
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cancelIfTerminating(); |
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} |
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s = status; |
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} |
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return s; |
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} |
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|
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/** |
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* Blocks a non-worker-thread until completion. |
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*/ |
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private void externalAwaitDone() { |
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int s; |
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while ((s = status) >= 0) { |
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synchronized(this) { |
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synchronized (this) { |
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if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){ |
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boolean interrupted = false; |
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while (status >= 0) { |
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/** |
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* Commences performing this task, awaits its completion if |
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* necessary, and return its result, or throws an (unchecked) |
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* exception if the underlying computation did so. |
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* necessary, and returns its result, or throws an (unchecked) |
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* {@code RuntimeException} or {@code Error} if the underlying |
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* computation did so. |
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* |
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* @return the computed result |
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*/ |
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/** |
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* Forks the given tasks, returning when {@code isDone} holds for |
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* each task or an (unchecked) exception is encountered, in which |
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* case the exception is rethrown. If either task encounters an |
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* exception, the other one may be, but is not guaranteed to be, |
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* cancelled. If both tasks throw an exception, then this method |
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* throws one of them. The individual status of each task may be |
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* checked using {@link #getException()} and related methods. |
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* case the exception is rethrown. If more than one task |
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* encounters an exception, then this method throws any one of |
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* these exceptions. If any task encounters an exception, the |
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* other may be cancelled. However, the execution status of |
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* individual tasks is not guaranteed upon exceptional return. The |
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* status of each task may be obtained using {@link |
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* #getException()} and related methods to check if they have been |
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* cancelled, completed normally or exceptionally, or left |
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* unprocessed. |
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* |
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* <p>This method may be invoked only from within {@code |
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* ForkJoinTask} computations (as may be determined using method |
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/** |
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* Forks the given tasks, returning when {@code isDone} holds for |
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* each task or an (unchecked) exception is encountered, in which |
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* case the exception is rethrown. If any task encounters an |
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* exception, others may be, but are not guaranteed to be, |
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* cancelled. If more than one task encounters an exception, then |
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* this method throws any one of these exceptions. The individual |
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* status of each task may be checked using {@link #getException()} |
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* and related methods. |
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* case the exception is rethrown. If more than one task |
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* encounters an exception, then this method throws any one of |
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* these exceptions. If any task encounters an exception, others |
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* may be cancelled. However, the execution status of individual |
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* tasks is not guaranteed upon exceptional return. The status of |
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* each task may be obtained using {@link #getException()} and |
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* related methods to check if they have been cancelled, completed |
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* normally or exceptionally, or left unprocessed. |
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* |
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* <p>This method may be invoked only from within {@code |
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* ForkJoinTask} computations (as may be determined using method |
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/** |
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* Forks all tasks in the specified collection, returning when |
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* {@code isDone} holds for each task or an (unchecked) exception |
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* is encountered. If any task encounters an exception, others |
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* may be, but are not guaranteed to be, cancelled. If more than |
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* one task encounters an exception, then this method throws any |
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* one of these exceptions. The individual status of each task |
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* may be checked using {@link #getException()} and related |
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* methods. The behavior of this operation is undefined if the |
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* specified collection is modified while the operation is in |
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* progress. |
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* is encountered, in which case the exception is rethrown. If |
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* more than one task encounters an exception, then this method |
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* throws any one of these exceptions. If any task encounters an |
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* exception, others may be cancelled. However, the execution |
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* status of individual tasks is not guaranteed upon exceptional |
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* return. The status of each task may be obtained using {@link |
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* #getException()} and related methods to check if they have been |
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* cancelled, completed normally or exceptionally, or left |
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* unprocessed. |
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* |
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* <p>This method may be invoked only from within {@code |
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* ForkJoinTask} computations (as may be determined using method |
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} |
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/** |
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* Cancels ignoring exceptions if worker is terminating |
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* Cancels if current thread is a terminating worker thread, |
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* ignoring any exceptions thrown by cancel. |
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*/ |
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final void cancelIfTerminating() { |
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Thread t = Thread.currentThread(); |
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/** |
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* Completes this task, and if not already aborted or cancelled, |
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* returning a {@code null} result upon {@code join} and related |
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* operations. This method may be used to provide results for |
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* asynchronous tasks, or to provide alternative handling for |
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* tasks that would not otherwise complete normally. Its use in |
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* other situations is discouraged. This method is |
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* overridable, but overridden versions must invoke {@code super} |
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* implementation to maintain guarantees. |
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* returning the given value as the result of subsequent |
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* invocations of {@code join} and related operations. This method |
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* may be used to provide results for asynchronous tasks, or to |
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* provide alternative handling for tasks that would not otherwise |
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* complete normally. Its use in other situations is |
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* discouraged. This method is overridable, but overridden |
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* versions must invoke {@code super} implementation to maintain |
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* guarantees. |
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* |
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* @param value the result value for this task |
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*/ |
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setCompletion(NORMAL); |
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} |
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|
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/** |
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* Waits if necessary for the computation to complete, and then |
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* retrieves its result. |
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* |
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* @return the computed result |
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* @throws CancellationException if the computation was cancelled |
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* @throws ExecutionException if the computation threw an |
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* exception |
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* @throws InterruptedException if the current thread is not a |
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* member of a ForkJoinPool and was interrupted while waiting |
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*/ |
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public final V get() throws InterruptedException, ExecutionException { |
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quietlyJoin(); |
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if (Thread.interrupted()) |
658 |
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throw new InterruptedException(); |
659 |
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int s = status; |
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> |
int s; |
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> |
if (Thread.currentThread() instanceof ForkJoinWorkerThread) { |
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quietlyJoin(); |
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s = status; |
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} |
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else { |
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while ((s = status) >= 0) { |
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synchronized (this) { // interruptible form of awaitDone |
664 |
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if (UNSAFE.compareAndSwapInt(this, statusOffset, |
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s, SIGNAL)) { |
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while (status >= 0) |
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wait(); |
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} |
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} |
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} |
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} |
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if (s < NORMAL) { |
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Throwable ex; |
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if (s == CANCELLED) |
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return getRawResult(); |
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} |
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|
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/** |
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* Waits if necessary for at most the given time for the computation |
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* to complete, and then retrieves its result, if available. |
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* |
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* @param timeout the maximum time to wait |
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* @param unit the time unit of the timeout argument |
688 |
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* @return the computed result |
689 |
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* @throws CancellationException if the computation was cancelled |
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* @throws ExecutionException if the computation threw an |
691 |
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* exception |
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* @throws InterruptedException if the current thread is not a |
693 |
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* member of a ForkJoinPool and was interrupted while waiting |
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* @throws TimeoutException if the wait timed out |
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*/ |
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public final V get(long timeout, TimeUnit unit) |
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throws InterruptedException, ExecutionException, TimeoutException { |
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Thread t = Thread.currentThread(); |
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*/ |
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boolean interrupted = false; |
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boolean dec = false; // true if pool count decremented |
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long nanos = unit.toNanos(timeout); |
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for (;;) { |
719 |
< |
if (Thread.interrupted() && pool == null) { |
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> |
if (pool == null && Thread.interrupted()) { |
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interrupted = true; |
721 |
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break; |
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} |
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break; |
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if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) { |
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long startTime = System.nanoTime(); |
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long nanos = unit.toNanos(timeout); |
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long nt; // wait time |
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while (status >= 0 && |
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(nt = nanos - (System.nanoTime() - startTime)) > 0) { |
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long ms = nt / 1000000; |
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int ns = (int) (nt % 1000000); |
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try { |
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< |
synchronized(this) { |
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> |
synchronized (this) { |
738 |
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if (status >= 0) |
739 |
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wait(ms, ns); |
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} |
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/** |
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* Commences performing this task and awaits its completion if |
803 |
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* necessary, without returning its result or throwing its |
804 |
< |
* exception. This method may be useful when processing |
734 |
< |
* collections of tasks when some have been cancelled or otherwise |
735 |
< |
* known to have aborted. |
804 |
> |
* exception. |
805 |
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*/ |
806 |
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public final void quietlyInvoke() { |
807 |
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if (status >= 0) { |
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private static final long serialVersionUID = -7721805057305804111L; |
1139 |
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|
1140 |
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/** |
1141 |
< |
* Saves the state to a stream. |
1141 |
> |
* Saves the state to a stream (that is, serializes it). |
1142 |
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* |
1143 |
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* @serialData the current run status and the exception thrown |
1144 |
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* during execution, or {@code null} if none |
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} |
1152 |
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|
1153 |
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/** |
1154 |
< |
* Reconstitutes the instance from a stream. |
1154 |
> |
* Reconstitutes the instance from a stream (that is, deserializes it). |
1155 |
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* |
1156 |
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* @param s the stream |
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*/ |