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/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/licenses/publicdomain
 */

package scala.actors.threadpool;

import scala.actors.threadpool.helpers.*;
import java.util.Collection;
import java.util.ArrayList;
import java.util.List;
import java.util.Iterator;

/**
 * Provides default implementations of {@link ExecutorService}
 * execution methods. This class implements the submit,
 * invokeAny and invokeAll methods using a
 * {@link RunnableFuture} returned by newTaskFor, which defaults
 * to the {@link FutureTask} class provided in this package.  For example,
 * the implementation of submit(Runnable) creates an
 * associated RunnableFuture that is executed and
 * returned. Subclasses may override the newTaskFor methods
 * to return RunnableFuture implementations other than
 * FutureTask.
 *
 * 

Extension example. Here is a sketch of a class * that customizes {@link ThreadPoolExecutor} to use * a CustomTask class instead of the default FutureTask: *

 * public class CustomThreadPoolExecutor extends ThreadPoolExecutor {
 *
 *   static class CustomTask<V> implements RunnableFuture<V> {...}
 *
 *   protected <V> RunnableFuture<V> newTaskFor(Callable<V> c) {
 *       return new CustomTask<V>(c);
 *   }
 *   protected <V> RunnableFuture<V> newTaskFor(Runnable r, V v) {
 *       return new CustomTask<V>(r, v);
 *   }
 *   // ... add constructors, etc.
 * }
 * 
* @since 1.5 * @author Doug Lea */ public abstract class AbstractExecutorService implements ExecutorService { /** * Returns a RunnableFuture for the given runnable and default * value. * * @param runnable the runnable task being wrapped * @param value the default value for the returned future * @return a RunnableFuture which when run will run the * underlying runnable and which, as a Future, will yield * the given value as its result and provide for cancellation of * the underlying task. * @since 1.6 */ protected RunnableFuture newTaskFor(Runnable runnable, Object value) { return new FutureTask(runnable, value); } /** * Returns a RunnableFuture for the given callable task. * * @param callable the callable task being wrapped * @return a RunnableFuture which when run will call the * underlying callable and which, as a Future, will yield * the callable's result as its result and provide for * cancellation of the underlying task. * @since 1.6 */ protected RunnableFuture newTaskFor(Callable callable) { return new FutureTask(callable); } /** * @throws RejectedExecutionException {@inheritDoc} * @throws NullPointerException {@inheritDoc} */ public Future submit(Runnable task) { if (task == null) throw new NullPointerException(); RunnableFuture ftask = newTaskFor(task, null); execute(ftask); return ftask; } /** * @throws RejectedExecutionException {@inheritDoc} * @throws NullPointerException {@inheritDoc} */ public Future submit(Runnable task, Object result) { if (task == null) throw new NullPointerException(); RunnableFuture ftask = newTaskFor(task, result); execute(ftask); return ftask; } /** * @throws RejectedExecutionException {@inheritDoc} * @throws NullPointerException {@inheritDoc} */ public Future submit(Callable task) { if (task == null) throw new NullPointerException(); RunnableFuture ftask = newTaskFor(task); execute(ftask); return ftask; } /** * the main mechanics of invokeAny. */ private Object doInvokeAny(Collection tasks, boolean timed, long nanos) throws InterruptedException, ExecutionException, TimeoutException { if (tasks == null) throw new NullPointerException(); int ntasks = tasks.size(); if (ntasks == 0) throw new IllegalArgumentException(); List futures = new ArrayList(ntasks); ExecutorCompletionService ecs = new ExecutorCompletionService(this); // For efficiency, especially in executors with limited // parallelism, check to see if previously submitted tasks are // done before submitting more of them. This interleaving // plus the exception mechanics account for messiness of main // loop. try { // Record exceptions so that if we fail to obtain any // result, we can throw the last exception we got. ExecutionException ee = null; long lastTime = (timed)? Utils.nanoTime() : 0; Iterator it = tasks.iterator(); // Start one task for sure; the rest incrementally futures.add(ecs.submit((Callable)it.next())); --ntasks; int active = 1; for (;;) { Future f = ecs.poll(); if (f == null) { if (ntasks > 0) { --ntasks; futures.add(ecs.submit((Callable)it.next())); ++active; } else if (active == 0) break; else if (timed) { f = ecs.poll(nanos, TimeUnit.NANOSECONDS); if (f == null) throw new TimeoutException(); long now = Utils.nanoTime(); nanos -= now - lastTime; lastTime = now; } else f = ecs.take(); } if (f != null) { --active; try { return f.get(); } catch (InterruptedException ie) { throw ie; } catch (ExecutionException eex) { ee = eex; } catch (RuntimeException rex) { ee = new ExecutionException(rex); } } } if (ee == null) ee = new ExecutionException(); throw ee; } finally { for (Iterator f = futures.iterator(); f.hasNext();) ((Future)f.next()).cancel(true); } } public Object invokeAny(Collection tasks) throws InterruptedException, ExecutionException { try { return doInvokeAny(tasks, false, 0); } catch (TimeoutException cannotHappen) { assert false; return null; } } public Object invokeAny(Collection tasks, long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException { return doInvokeAny(tasks, true, unit.toNanos(timeout)); } public List invokeAll(Collection tasks) throws InterruptedException { if (tasks == null) throw new NullPointerException(); List futures = new ArrayList(tasks.size()); boolean done = false; try { for (Iterator t = tasks.iterator(); t.hasNext();) { RunnableFuture f = newTaskFor((Callable)t.next()); futures.add(f); execute(f); } for (Iterator i = futures.iterator(); i.hasNext();) { Future f = (Future) i.next(); if (!f.isDone()) { try { f.get(); } catch (CancellationException ignore) { } catch (ExecutionException ignore) { } } } done = true; return futures; } finally { if (!done) for (Iterator i = futures.iterator(); i.hasNext();) { Future f = (Future) i.next(); f.cancel(true); } } } public List invokeAll(Collection tasks, long timeout, TimeUnit unit) throws InterruptedException { if (tasks == null || unit == null) throw new NullPointerException(); long nanos = unit.toNanos(timeout); List futures = new ArrayList(tasks.size()); boolean done = false; try { for (Iterator t = tasks.iterator(); t.hasNext();) futures.add(newTaskFor((Callable)t.next())); long lastTime = Utils.nanoTime(); // Interleave time checks and calls to execute in case // executor doesn't have any/much parallelism. Iterator it = futures.iterator(); while (it.hasNext()) { execute((Runnable)(it.next())); long now = Utils.nanoTime(); nanos -= (now - lastTime); lastTime = now; if (nanos <= 0) return futures; } for (Iterator i = futures.iterator(); i.hasNext();) { Future f = (Future)i.next(); if (!f.isDone()) { if (nanos <= 0) return futures; try { f.get(nanos, TimeUnit.NANOSECONDS); } catch (CancellationException ignore) { } catch (ExecutionException ignore) { } catch (TimeoutException toe) { return futures; } long now = Utils.nanoTime(); nanos -= now - lastTime; lastTime = now; } } done = true; return futures; } finally { if (!done) for (Iterator i = futures.iterator(); i.hasNext();) { Future f = (Future) i.next(); f.cancel(true); } } } }




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