/* * Copyright (c) 2008, 2009, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */package sun.nio.fs;import sun.misc.Unsafe;import java.util.concurrent.ExecutionException;/** * Base implementation of a task (typically native) that polls a memory location * during execution so that it may be aborted/cancelled before completion. The * task is executed by invoking the {@link runInterruptibly} method defined * here and cancelled by invoking Thread.interrupt. */abstract class Cancellable implements Runnable { private static final Unsafe unsafe = Unsafe.getUnsafe(); private final long pollingAddress; private final Object lock = new Object(); // the following require lock when examining or changing private boolean completed; private Throwable exception; protected Cancellable() { pollingAddress = unsafe.allocateMemory(4); unsafe.putIntVolatile(null, pollingAddress, 0); } /** * Returns the memory address of a 4-byte int that should be polled to * detect cancellation. */ protected long addressToPollForCancel() { return pollingAddress; } /** * The value to write to the polled memory location to indicate that the * task has been cancelled. If this method is not overridden then it * defaults to MAX_VALUE. */ protected int cancelValue() { return Integer.MAX_VALUE; } /** * "cancels" the task by writing bits into memory location that it polled * by the task. */ final void cancel() { synchronized (lock) { if (!completed) { unsafe.putIntVolatile(null, pollingAddress, cancelValue()); } } } /** * Returns the exception thrown by the task or null if the task completed * successfully. */ private Throwable exception() { synchronized (lock) { return exception; } } @Override public final void run() { try { implRun(); } catch (Throwable t) { synchronized (lock) { exception = t; } } finally { synchronized (lock) { completed = true; unsafe.freeMemory(pollingAddress); } } } /** * The task body. This should periodically poll the memory location * to check for cancellation. */ abstract void implRun() throws Throwable; /** * Invokes the given task in its own thread. If this (meaning the current) * thread is interrupted then an attempt is make to cancel the background * thread by writing into the memory location that it polls cooperatively. */ static void runInterruptibly(Cancellable task) throws ExecutionException { Thread t = new Thread(task); t.start(); boolean cancelledByInterrupt = false; while (t.isAlive()) { try { t.join(); } catch (InterruptedException e) { cancelledByInterrupt = true; task.cancel(); } } if (cancelledByInterrupt) Thread.currentThread().interrupt(); Throwable exc = task.exception(); if (exc != null) throw new ExecutionException(exc); }}
/*
* Copyright (c) 2008, 2009, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package sun.nio.fs;
import sun.misc.Unsafe;
import java.util.concurrent.ExecutionException;
/**
* Base implementation of a task (typically native) that polls a memory location
* during execution so that it may be aborted/cancelled before completion. The
* task is executed by invoking the {@link runInterruptibly} method defined
* here and cancelled by invoking Thread.interrupt.
*/
abstract class Cancellable implements Runnable {
private static final Unsafe unsafe = Unsafe.getUnsafe();
private final long pollingAddress;
private final Object lock = new Object();
// the following require lock when examining or changing
private boolean completed;
private Throwable exception;
protected Cancellable() {
pollingAddress = unsafe.allocateMemory(4);
unsafe.putIntVolatile(null, pollingAddress, 0);
}
/**
* Returns the memory address of a 4-byte int that should be polled to
* detect cancellation.
*/
protected long addressToPollForCancel() {
return pollingAddress;
}
/**
* The value to write to the polled memory location to indicate that the
* task has been cancelled. If this method is not overridden then it
* defaults to MAX_VALUE.
*/
protected int cancelValue() {
return Integer.MAX_VALUE;
}
/**
* "cancels" the task by writing bits into memory location that it polled
* by the task.
*/
final void cancel() {
synchronized (lock) {
if (!completed) {
unsafe.putIntVolatile(null, pollingAddress, cancelValue());
}
}
}
/**
* Returns the exception thrown by the task or null if the task completed
* successfully.
*/
private Throwable exception() {
synchronized (lock) {
return exception;
}
}
@Override
public final void run() {
try {
implRun();
} catch (Throwable t) {
synchronized (lock) {
exception = t;
}
} finally {
synchronized (lock) {
completed = true;
unsafe.freeMemory(pollingAddress);
}
}
}
/**
* The task body. This should periodically poll the memory location
* to check for cancellation.
*/
abstract void implRun() throws Throwable;
/**
* Invokes the given task in its own thread. If this (meaning the current)
* thread is interrupted then an attempt is make to cancel the background
* thread by writing into the memory location that it polls cooperatively.
*/
static void runInterruptibly(Cancellable task) throws ExecutionException {
Thread t = new Thread(task);
t.start();
boolean cancelledByInterrupt = false;
while (t.isAlive()) {
try {
t.join();
} catch (InterruptedException e) {
cancelledByInterrupt = true;
task.cancel();
}
}
if (cancelledByInterrupt)
Thread.currentThread().interrupt();
Throwable exc = task.exception();
if (exc != null)
throw new ExecutionException(exc);
}
}