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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* |
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*/ |
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|
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package jsr166y.forkjoin; |
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import java.util.*; |
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import java.util.concurrent.*; |
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import java.util.concurrent.atomic.*; |
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|
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/** |
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* A minimal skeleton for AsyncActions. Instances of BasicAsyncAction |
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* maintain a single atomic integer task state that may be used to |
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* control activities. Task state is initially zero, or negative if |
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* this task has been cancelled. Once negative, the value cannot be |
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* changed. |
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*/ |
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public abstract class BasicAsyncAction extends AsyncAction { |
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/** |
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* Gets the task state, which is initially zero, or negative if |
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* this task has been cancelled. Once negative, the value cannot |
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* be changed. |
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* @return task state |
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*/ |
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protected final int getTaskState() { |
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return status; |
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} |
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|
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/** |
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* Atomically sets the task state to the given nonnegative updated |
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* value if the current value is non-negative and equal to the |
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* expected value. |
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* @param expect the expected value |
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* @param update the new value |
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* @return true if successful |
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*/ |
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protected final boolean compareAndSetTaskState(int expect, int update) { |
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return update >= 0 && casStatus(expect, update); |
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} |
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|
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/** |
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* Sets the task state to the given nonnegative value, assuming |
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* that no other thread is concurrently accessing this task. The |
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* effects under any other usage are undefined. This method is |
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* typically only useful for initializing state values. |
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* @param value the new value |
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* @throws IllegalArgumentException if value negative |
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*/ |
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protected final void setTaskState(int value) { |
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if (value < 0) throw new IllegalArgumentException(); |
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setStatus(value); |
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} |
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|
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/** |
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* Sets task state to indicate completion |
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*/ |
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public void finish() { |
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setDone(); |
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} |
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|
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/** |
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* Sets task state to indicate completion with the given exception |
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*/ |
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public void finishExceptionally(Throwable ex) { |
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checkedSetDoneExceptionally(ex); |
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} |
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|
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final boolean exec() { |
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if (status >= 0) { |
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try { |
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compute(); |
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} catch(Throwable rex) { |
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setDoneExceptionally(rex); |
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} |
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} |
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return false; |
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} |
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|
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} |
