ThreadState.java

/*
 * Copyright (c) 2014, 2018, 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.
 *
 * 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 nsk.share.jdi;

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.TimeUnit;

import nsk.share.Failure;

/**
 * Functions to set and wait for states in threads.
 * Used to sync main thread and debuggee thread.
 */
public class ThreadState {
    private final Lock lock = new ReentrantLock();
    private final Condition cond = lock.newCondition();
    private volatile String currentState;
    private long timeoutMs;

    public ThreadState(String startState, long timeoutMs) {
        currentState = startState;
        this.timeoutMs = timeoutMs;
    }

    /**
     * Set new state.
     */
    public void setState(String newState) {
        lock.lock();
        try {
            log(MSG_SET_STATE, newState);
            currentState = newState;
            cond.signalAll();
        } finally {
            lock.unlock();
        }
    }

    /**
     * Wait for the specified state.
     * Throws Failure if timeout.
     */
    public void waitForState(String waitState) {
        lock.lock();
        try {
            log(MSG_WAIT_STATE, waitState);
            while (!currentState.equals(waitState)) {
                if (!cond.await(timeoutMs, TimeUnit.MILLISECONDS)) {
                    throw new Failure(format(MSG_TIMEOUT, waitState));
                }
            }
            log(MSG_GOT_STATE, waitState);
        } catch (InterruptedException e) {
            e.printStackTrace();
            throw new Failure(e);
        } finally {
            lock.unlock();
        }
    }

    /**
     * Simple helper that sets a new state and then wait for another state.
     */
    public void setAndWait(String newState, String waitState) {
        setState(newState);
        waitForState(waitState);
    }

    private static final String MSG_TIMEOUT = "ThreadState(thread='%s', state='%s') timeout waiting for %s";
    private static final String MSG_SET_STATE = "ThreadState(thread='%s', state='%s') set state to %s";
    private static final String MSG_WAIT_STATE = "ThreadState(thread='%s', state='%s') waiting for state %s";
    private static final String MSG_GOT_STATE = "ThreadState(thread='%s', state='%s') got state %s";

    private String format(String pattern, String state) {
        final String threadName = Thread.currentThread().getName();
        return String.format(pattern, threadName, currentState, state);
    }

    private void log(String pattern, String state) {
        System.out.println(format(pattern, state));
    }
}