| /* |
| * Copyright (c) 2016, 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 jdk.incubator.http.internal.websocket; |
| |
| import java.util.concurrent.atomic.AtomicLong; |
| |
| import static java.util.Objects.requireNonNull; |
| |
| final class CooperativeHandler { |
| |
| private static final long CONTINUE = 0; |
| private static final long OFF = 1; |
| private static final long ON = 2; |
| private static final long STOP = 4; |
| |
| private final AtomicLong state = new AtomicLong(OFF); |
| |
| private final Runnable task; |
| |
| CooperativeHandler(Runnable task) { |
| this.task = requireNonNull(task); |
| } |
| |
| /* |
| * Causes the task supplied to the constructor to run. The task may be run |
| * by this thread as well as by any other that has invoked this method. |
| * |
| * The recursion which is possible here will have the maximum depth of 1: |
| * |
| * task.run() |
| * this.startOrContinue() |
| * task.run() |
| */ |
| void startOrContinue() { |
| long s; |
| while (true) { |
| s = state.get(); |
| if (s == OFF && state.compareAndSet(OFF, ON)) { |
| // No one is running the task, we are going to run it |
| break; |
| } |
| if (s == ON && state.compareAndSet(ON, CONTINUE)) { |
| // Some other thread is running the task. We have managed to |
| // update the state, it will be surely noticed by that thread. |
| return; |
| } |
| if (s == CONTINUE || s == STOP) { |
| return; |
| } |
| } |
| while (true) { |
| task.run(); |
| // State checks are ordered by the probability of expected values |
| // (it might be different in different usage patterns, say, when |
| // invocations to `startOrContinue()` are concurrent) |
| if (state.compareAndSet(ON, OFF)) { |
| break; // The state hasn't changed, all done |
| } |
| if (state.compareAndSet(CONTINUE, ON)) { |
| continue; |
| } |
| // Other threads can change the state from CONTINUE to STOP only |
| // So if it's not ON and not CONTINUE, it can only be STOP |
| break; |
| } |
| } |
| |
| void stop() { |
| state.set(STOP); |
| } |
| } |