Latch.java

/**
 * Copyright 2007-2015, Kaazing Corporation. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.kaazing.k3po.driver.internal.test.utils;

import java.util.concurrent.CountDownLatch;

class Latch {

    enum State {
        INIT, PREPARED, STARTABLE, FINISHED
    }

    private volatile State state;
    private volatile Exception exception;

    private final CountDownLatch prepared;
    private final CountDownLatch startable;
    private final CountDownLatch finished;

    Latch() {
        state = State.INIT;

        prepared = new CountDownLatch(1);
        startable = new CountDownLatch(1);
        finished = new CountDownLatch(1);
    }

    void notifyPrepared() {
        switch (state) {
        case INIT:
            state = State.PREPARED;
            prepared.countDown();
            break;
        default:
            throw new IllegalStateException(state.name());
        }
    }

    void awaitPrepared() throws Exception {
        prepared.await();
        if (exception != null) {
            throw exception;
        }
    }

    boolean isPrepared() {
        return prepared.getCount() == 0L;
    }

    void notifyStartable() {
        switch (state) {
        case PREPARED:
            state = State.STARTABLE;
            startable.countDown();
            break;
        case STARTABLE:
        case FINISHED:
            // its all right to call this multiple times if its prepared
            break;
        default:
            throw new IllegalStateException(state.name());
        }
    }

    void awaitStartable() throws Exception {
        startable.await();
        if (exception != null) {
            throw exception;
        }
    }

    boolean isStartable() {
        return startable.getCount() == 0L;
    }

    void notifyFinished() {
        switch (state) {
        case INIT:
            notifyPrepared();
            break;
        // We could abort before started.
        case PREPARED:
        case STARTABLE:
            state = State.FINISHED;
            finished.countDown();
            break;
        default:
            throw new IllegalStateException(state.name());
        }
    }

    void notifyAbort() {
        switch (state) {
        case INIT:
            notifyPrepared();
        case PREPARED:
            notifyStartable();
            break;
        default:
        }
    }

    void awaitFinished() throws Exception {
        finished.await();
        if (exception != null) {
            throw exception;
        }
    }

    boolean isFinished() {
        return finished.getCount() == 0L;
    }

    boolean hasException() {
        return exception != null;
    }

    void notifyException(Exception exception) {
        this.exception = exception;
        prepared.countDown();
        startable.countDown();
        finished.countDown();
    }
}