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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
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package com.sun.grizzly.impl;

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

/**
 * {@link Future} implementation with the specific unmodifiable result.
 *
 * @see Future
 * 
 * @author Alexey Stashok
 */
public class ReadyFutureImpl implements Future {

    protected final R result;
    private final Throwable failure;
    private final boolean isCancelled;

    /**
     * Construct cancelled {@link Future}.
     */
    public ReadyFutureImpl() {
        this(null, null, true);
    }

    /**
     * Construct {@link Future} with the result.
     */
    public ReadyFutureImpl(R result) {
        this(result, null, false);
    }

    /**
     * Construct failed {@link Future}.
     */
    public ReadyFutureImpl(Throwable failure) {
        this(null, failure, false);
    }

    protected ReadyFutureImpl(R result, Throwable failure,
            boolean isCancelled) {
        this.result = result;
        this.failure = failure;
        this.isCancelled = isCancelled;
    }

    /**
     * Get current result value without any blocking.
     *
     * @return current result value without any blocking.
     */
    public R getResult() {
        return result;
    }

    /**
     * Should not be called for ReadyFutureImpl
     */
    public void setResult(R result) {
        throw new IllegalStateException("Can not be reset on ReadyFutureImpl");
    }

    /**
     * Do nothing.
     * 
     * @return cancel state, which was set during construction.
     */
    public boolean cancel(boolean mayInterruptIfRunning) {
        return isCancelled;
    }

    /**
     * {@inheritDoc}
     */
    public boolean isCancelled() {
        return isCancelled;
    }

    /**
     * {@inheritDoc}
     */
    public boolean isDone() {
        return true;
    }

    /**
     * {@inheritDoc}
     */
    public R get() throws InterruptedException, ExecutionException {
        if (isCancelled) {
            throw new CancellationException();
        } else if (failure != null) {
            throw new ExecutionException(failure);
        }

        return result;
    }

    /**
     * {@inheritDoc}
     */
    public R get(long timeout, TimeUnit unit) throws
            InterruptedException, ExecutionException, TimeoutException {
        if (isCancelled) {
            throw new CancellationException();
        } else if (failure != null) {
            throw new ExecutionException(failure);
        } else if (result != null) {
            return result;
        } else {
            throw new TimeoutException();
        }
    }

    /**
     * Should not be called for ReadyFutureImpl
     */
    public void failure(Throwable failure) {
        throw new IllegalStateException("Can not be reset on ReadyFutureImpl");
    }
}