BasicFuture.java

/*
 * 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 com.ok2c.lightnio.concurrent;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

public class BasicFuture<T> implements Future<T> {

    private final FutureCallback<T> callback;

    private volatile boolean completed;
    private volatile boolean cancelled;
    private volatile T result;
    private volatile Exception ex;

    public BasicFuture(final FutureCallback<T> callback) {
        super();
        this.callback = callback;
    }

    public boolean isCancelled() {
        return this.cancelled;
    }

    public boolean isDone() {
        return this.completed;
    }

    private T getResult() throws ExecutionException {
        if (this.ex != null) {
            throw new ExecutionException(this.ex);
        }
        return this.result;
    }

    public synchronized T get() throws InterruptedException, ExecutionException {
        while (!this.completed) {
            wait();
        }
        return getResult();
    }

    public synchronized T get(long timeout, final TimeUnit unit)
            throws InterruptedException, ExecutionException, TimeoutException {
        long msecs = unit.toMillis(timeout);
        long startTime = (msecs <= 0) ? 0 : System.currentTimeMillis();
        long waitTime = msecs;
        if (this.completed) {
            return getResult();
        } else if (waitTime <= 0) {
            throw new TimeoutException();
        } else {
            for (;;) {
                wait(waitTime);
                if (this.completed) {
                    return getResult();
                } else {
                    waitTime = msecs - (System.currentTimeMillis() - startTime);
                    if (waitTime <= 0) {
                        throw new TimeoutException();
                    }
                }
            }
        }
    }

    public synchronized boolean completed(final T result) {
        if (this.completed) {
            return false;
        }
        this.completed = true;
        this.result = result;
        if (this.callback != null) {
            this.callback.completed(result);
        }
        notifyAll();
        return true;
    }

    public synchronized boolean failed(final Exception exception) {
        if (this.completed) {
            return false;
        }
        this.completed = true;
        this.ex = exception;
        if (this.callback != null) {
            this.callback.failed(exception);
        }
        notifyAll();
        return true;
    }

    public synchronized boolean cancel(boolean mayInterruptIfRunning) {
        if (this.completed) {
            return false;
        }
        this.completed = true;
        this.cancelled = true;
        if (this.callback != null) {
            this.callback.cancelled();
        }
        notifyAll();
        return true;
    }

}