1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/rt/emul/compact/src/main/java/java/util/concurrent/FutureTask.java Sat Mar 19 10:46:31 2016 +0100
1.3 @@ -0,0 +1,360 @@
1.4 +/*
1.5 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.6 + *
1.7 + * This code is free software; you can redistribute it and/or modify it
1.8 + * under the terms of the GNU General Public License version 2 only, as
1.9 + * published by the Free Software Foundation. Oracle designates this
1.10 + * particular file as subject to the "Classpath" exception as provided
1.11 + * by Oracle in the LICENSE file that accompanied this code.
1.12 + *
1.13 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.14 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.15 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.16 + * version 2 for more details (a copy is included in the LICENSE file that
1.17 + * accompanied this code).
1.18 + *
1.19 + * You should have received a copy of the GNU General Public License version
1.20 + * 2 along with this work; if not, write to the Free Software Foundation,
1.21 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.22 + *
1.23 + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
1.24 + * or visit www.oracle.com if you need additional information or have any
1.25 + * questions.
1.26 + */
1.27 +
1.28 +/*
1.29 + * This file is available under and governed by the GNU General Public
1.30 + * License version 2 only, as published by the Free Software Foundation.
1.31 + * However, the following notice accompanied the original version of this
1.32 + * file:
1.33 + *
1.34 + * Written by Doug Lea with assistance from members of JCP JSR-166
1.35 + * Expert Group and released to the public domain, as explained at
1.36 + * http://creativecommons.org/publicdomain/zero/1.0/
1.37 + */
1.38 +
1.39 +package java.util.concurrent;
1.40 +import java.util.concurrent.locks.*;
1.41 +
1.42 +/**
1.43 + * A cancellable asynchronous computation. This class provides a base
1.44 + * implementation of {@link Future}, with methods to start and cancel
1.45 + * a computation, query to see if the computation is complete, and
1.46 + * retrieve the result of the computation. The result can only be
1.47 + * retrieved when the computation has completed; the <tt>get</tt>
1.48 + * method will block if the computation has not yet completed. Once
1.49 + * the computation has completed, the computation cannot be restarted
1.50 + * or cancelled.
1.51 + *
1.52 + * <p>A <tt>FutureTask</tt> can be used to wrap a {@link Callable} or
1.53 + * {@link java.lang.Runnable} object. Because <tt>FutureTask</tt>
1.54 + * implements <tt>Runnable</tt>, a <tt>FutureTask</tt> can be
1.55 + * submitted to an {@link Executor} for execution.
1.56 + *
1.57 + * <p>In addition to serving as a standalone class, this class provides
1.58 + * <tt>protected</tt> functionality that may be useful when creating
1.59 + * customized task classes.
1.60 + *
1.61 + * @since 1.5
1.62 + * @author Doug Lea
1.63 + * @param <V> The result type returned by this FutureTask's <tt>get</tt> method
1.64 + */
1.65 +public class FutureTask<V> implements RunnableFuture<V> {
1.66 + /** Synchronization control for FutureTask */
1.67 + private final Sync sync;
1.68 +
1.69 + /**
1.70 + * Creates a <tt>FutureTask</tt> that will, upon running, execute the
1.71 + * given <tt>Callable</tt>.
1.72 + *
1.73 + * @param callable the callable task
1.74 + * @throws NullPointerException if callable is null
1.75 + */
1.76 + public FutureTask(Callable<V> callable) {
1.77 + if (callable == null)
1.78 + throw new NullPointerException();
1.79 + sync = new Sync(callable);
1.80 + }
1.81 +
1.82 + /**
1.83 + * Creates a <tt>FutureTask</tt> that will, upon running, execute the
1.84 + * given <tt>Runnable</tt>, and arrange that <tt>get</tt> will return the
1.85 + * given result on successful completion.
1.86 + *
1.87 + * @param runnable the runnable task
1.88 + * @param result the result to return on successful completion. If
1.89 + * you don't need a particular result, consider using
1.90 + * constructions of the form:
1.91 + * {@code Future<?> f = new FutureTask<Void>(runnable, null)}
1.92 + * @throws NullPointerException if runnable is null
1.93 + */
1.94 + public FutureTask(Runnable runnable, V result) {
1.95 + sync = new Sync(Executors.callable(runnable, result));
1.96 + }
1.97 +
1.98 + public boolean isCancelled() {
1.99 + return sync.innerIsCancelled();
1.100 + }
1.101 +
1.102 + public boolean isDone() {
1.103 + return sync.innerIsDone();
1.104 + }
1.105 +
1.106 + public boolean cancel(boolean mayInterruptIfRunning) {
1.107 + return sync.innerCancel(mayInterruptIfRunning);
1.108 + }
1.109 +
1.110 + /**
1.111 + * @throws CancellationException {@inheritDoc}
1.112 + */
1.113 + public V get() throws InterruptedException, ExecutionException {
1.114 + return sync.innerGet();
1.115 + }
1.116 +
1.117 + /**
1.118 + * @throws CancellationException {@inheritDoc}
1.119 + */
1.120 + public V get(long timeout, TimeUnit unit)
1.121 + throws InterruptedException, ExecutionException, TimeoutException {
1.122 + return sync.innerGet(unit.toNanos(timeout));
1.123 + }
1.124 +
1.125 + /**
1.126 + * Protected method invoked when this task transitions to state
1.127 + * <tt>isDone</tt> (whether normally or via cancellation). The
1.128 + * default implementation does nothing. Subclasses may override
1.129 + * this method to invoke completion callbacks or perform
1.130 + * bookkeeping. Note that you can query status inside the
1.131 + * implementation of this method to determine whether this task
1.132 + * has been cancelled.
1.133 + */
1.134 + protected void done() { }
1.135 +
1.136 + /**
1.137 + * Sets the result of this Future to the given value unless
1.138 + * this future has already been set or has been cancelled.
1.139 + * This method is invoked internally by the <tt>run</tt> method
1.140 + * upon successful completion of the computation.
1.141 + * @param v the value
1.142 + */
1.143 + protected void set(V v) {
1.144 + sync.innerSet(v);
1.145 + }
1.146 +
1.147 + /**
1.148 + * Causes this future to report an <tt>ExecutionException</tt>
1.149 + * with the given throwable as its cause, unless this Future has
1.150 + * already been set or has been cancelled.
1.151 + * This method is invoked internally by the <tt>run</tt> method
1.152 + * upon failure of the computation.
1.153 + * @param t the cause of failure
1.154 + */
1.155 + protected void setException(Throwable t) {
1.156 + sync.innerSetException(t);
1.157 + }
1.158 +
1.159 + // The following (duplicated) doc comment can be removed once
1.160 + //
1.161 + // 6270645: Javadoc comments should be inherited from most derived
1.162 + // superinterface or superclass
1.163 + // is fixed.
1.164 + /**
1.165 + * Sets this Future to the result of its computation
1.166 + * unless it has been cancelled.
1.167 + */
1.168 + public void run() {
1.169 + sync.innerRun();
1.170 + }
1.171 +
1.172 + /**
1.173 + * Executes the computation without setting its result, and then
1.174 + * resets this Future to initial state, failing to do so if the
1.175 + * computation encounters an exception or is cancelled. This is
1.176 + * designed for use with tasks that intrinsically execute more
1.177 + * than once.
1.178 + * @return true if successfully run and reset
1.179 + */
1.180 + protected boolean runAndReset() {
1.181 + return sync.innerRunAndReset();
1.182 + }
1.183 +
1.184 + /**
1.185 + * Synchronization control for FutureTask. Note that this must be
1.186 + * a non-static inner class in order to invoke the protected
1.187 + * <tt>done</tt> method. For clarity, all inner class support
1.188 + * methods are same as outer, prefixed with "inner".
1.189 + *
1.190 + * Uses AQS sync state to represent run status
1.191 + */
1.192 + private final class Sync extends AbstractQueuedSynchronizer {
1.193 + private static final long serialVersionUID = -7828117401763700385L;
1.194 +
1.195 + /** State value representing that task is ready to run */
1.196 + private static final int READY = 0;
1.197 + /** State value representing that task is running */
1.198 + private static final int RUNNING = 1;
1.199 + /** State value representing that task ran */
1.200 + private static final int RAN = 2;
1.201 + /** State value representing that task was cancelled */
1.202 + private static final int CANCELLED = 4;
1.203 +
1.204 + /** The underlying callable */
1.205 + private final Callable<V> callable;
1.206 + /** The result to return from get() */
1.207 + private V result;
1.208 + /** The exception to throw from get() */
1.209 + private Throwable exception;
1.210 +
1.211 + /**
1.212 + * The thread running task. When nulled after set/cancel, this
1.213 + * indicates that the results are accessible. Must be
1.214 + * volatile, to ensure visibility upon completion.
1.215 + */
1.216 + private volatile Thread runner;
1.217 +
1.218 + Sync(Callable<V> callable) {
1.219 + this.callable = callable;
1.220 + }
1.221 +
1.222 + private boolean ranOrCancelled(int state) {
1.223 + return (state & (RAN | CANCELLED)) != 0;
1.224 + }
1.225 +
1.226 + /**
1.227 + * Implements AQS base acquire to succeed if ran or cancelled
1.228 + */
1.229 + protected int tryAcquireShared(int ignore) {
1.230 + return innerIsDone() ? 1 : -1;
1.231 + }
1.232 +
1.233 + /**
1.234 + * Implements AQS base release to always signal after setting
1.235 + * final done status by nulling runner thread.
1.236 + */
1.237 + protected boolean tryReleaseShared(int ignore) {
1.238 + runner = null;
1.239 + return true;
1.240 + }
1.241 +
1.242 + boolean innerIsCancelled() {
1.243 + return getState() == CANCELLED;
1.244 + }
1.245 +
1.246 + boolean innerIsDone() {
1.247 + return ranOrCancelled(getState()) && runner == null;
1.248 + }
1.249 +
1.250 + V innerGet() throws InterruptedException, ExecutionException {
1.251 + acquireSharedInterruptibly(0);
1.252 + if (getState() == CANCELLED)
1.253 + throw new CancellationException();
1.254 + if (exception != null)
1.255 + throw new ExecutionException(exception);
1.256 + return result;
1.257 + }
1.258 +
1.259 + V innerGet(long nanosTimeout) throws InterruptedException, ExecutionException, TimeoutException {
1.260 + if (!tryAcquireSharedNanos(0, nanosTimeout))
1.261 + throw new TimeoutException();
1.262 + if (getState() == CANCELLED)
1.263 + throw new CancellationException();
1.264 + if (exception != null)
1.265 + throw new ExecutionException(exception);
1.266 + return result;
1.267 + }
1.268 +
1.269 + void innerSet(V v) {
1.270 + for (;;) {
1.271 + int s = getState();
1.272 + if (s == RAN)
1.273 + return;
1.274 + if (s == CANCELLED) {
1.275 + // aggressively release to set runner to null,
1.276 + // in case we are racing with a cancel request
1.277 + // that will try to interrupt runner
1.278 + releaseShared(0);
1.279 + return;
1.280 + }
1.281 + if (compareAndSetState(s, RAN)) {
1.282 + result = v;
1.283 + releaseShared(0);
1.284 + done();
1.285 + return;
1.286 + }
1.287 + }
1.288 + }
1.289 +
1.290 + void innerSetException(Throwable t) {
1.291 + for (;;) {
1.292 + int s = getState();
1.293 + if (s == RAN)
1.294 + return;
1.295 + if (s == CANCELLED) {
1.296 + // aggressively release to set runner to null,
1.297 + // in case we are racing with a cancel request
1.298 + // that will try to interrupt runner
1.299 + releaseShared(0);
1.300 + return;
1.301 + }
1.302 + if (compareAndSetState(s, RAN)) {
1.303 + exception = t;
1.304 + releaseShared(0);
1.305 + done();
1.306 + return;
1.307 + }
1.308 + }
1.309 + }
1.310 +
1.311 + boolean innerCancel(boolean mayInterruptIfRunning) {
1.312 + for (;;) {
1.313 + int s = getState();
1.314 + if (ranOrCancelled(s))
1.315 + return false;
1.316 + if (compareAndSetState(s, CANCELLED))
1.317 + break;
1.318 + }
1.319 + if (mayInterruptIfRunning) {
1.320 + Thread r = runner;
1.321 + if (r != null)
1.322 + r.interrupt();
1.323 + }
1.324 + releaseShared(0);
1.325 + done();
1.326 + return true;
1.327 + }
1.328 +
1.329 + void innerRun() {
1.330 + if (!compareAndSetState(READY, RUNNING))
1.331 + return;
1.332 +
1.333 + runner = Thread.currentThread();
1.334 + if (getState() == RUNNING) { // recheck after setting thread
1.335 + V result;
1.336 + try {
1.337 + result = callable.call();
1.338 + } catch (Throwable ex) {
1.339 + setException(ex);
1.340 + return;
1.341 + }
1.342 + set(result);
1.343 + } else {
1.344 + releaseShared(0); // cancel
1.345 + }
1.346 + }
1.347 +
1.348 + boolean innerRunAndReset() {
1.349 + if (!compareAndSetState(READY, RUNNING))
1.350 + return false;
1.351 + try {
1.352 + runner = Thread.currentThread();
1.353 + if (getState() == RUNNING)
1.354 + callable.call(); // don't set result
1.355 + runner = null;
1.356 + return compareAndSetState(RUNNING, READY);
1.357 + } catch (Throwable ex) {
1.358 + setException(ex);
1.359 + return false;
1.360 + }
1.361 + }
1.362 + }
1.363 +}