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/*

  * Written by Doug Lea with assistance from members of JCP JSR-166

  * Expert Group and released to the public domain, as explained at

  * http://creativecommons.org/licenses/publicdomain

  */

package java.util.concurrent;

/**

 * A <tt>TimeUnit</tt> represents time durations at a given unit of

 * granularity and provides utility methods to convert across units,

 * and to perform timing and delay operations in these units.  A

 * <tt>TimeUnit</tt> does not maintain time information, but only

 * helps organize and use time representations that may be maintained

 * separately across various contexts.  A nanosecond is defined as one

 * thousandth of a microsecond, a microsecond as one thousandth of a

 * millisecond, a millisecond as one thousandth of a second, a minute

 * as sixty seconds, an hour as sixty minutes, and a day as twenty four

 * hours.

 *

 * <p>A <tt>TimeUnit</tt> is mainly used to inform time-based methods

 * how a given timing parameter should be interpreted. For example,

 * the following code will timeout in 50 milliseconds if the {@link

 * java.util.concurrent.locks.Lock lock} is not available:

 *

 * <pre>  Lock lock = ...;

 *  if ( lock.tryLock(50L, TimeUnit.MILLISECONDS) ) ...

 * </pre>

 * while this code will timeout in 50 seconds:

 * <pre>

 *  Lock lock = ...;

 *  if ( lock.tryLock(50L, TimeUnit.SECONDS) ) ...

 * </pre>

 *

 * Note however, that there is no guarantee that a particular timeout

 * implementation will be able to notice the passage of time at the

 * same granularity as the given <tt>TimeUnit</tt>.

 *

 * @since 1.5

 * @author Doug Lea

 */

public enum TimeUnit {

    NANOSECONDS {

        public long toNanos(long d)   { return d; }

        public long toMicros(long d)  { return d/(C1/C0); }

        public long toMillis(long d)  { return d/(C2/C0); }

        public long toSeconds(long d) { return d/(C3/C0); }

        public long toMinutes(long d) { return d/(C4/C0); }

        public long toHours(long d)   { return d/(C5/C0); }

        public long toDays(long d)    { return d/(C6/C0); }

        public long convert(long d, TimeUnit u) { return u.toNanos(d); }

        int excessNanos(long d, long m) { return (int)(d - (m*C2)); }

    },

    MICROSECONDS {

        public long toNanos(long d)   { return x(d, C1/C0, MAX/(C1/C0)); }

        public long toMicros(long d)  { return d; }

        public long toMillis(long d)  { return d/(C2/C1); }

        public long toSeconds(long d) { return d/(C3/C1); }

        public long toMinutes(long d) { return d/(C4/C1); }

        public long toHours(long d)   { return d/(C5/C1); }

        public long toDays(long d)    { return d/(C6/C1); }

        public long convert(long d, TimeUnit u) { return u.toMicros(d); }

        int excessNanos(long d, long m) { return (int)((d*C1) - (m*C2)); }

    },

    MILLISECONDS {

        public long toNanos(long d)   { return x(d, C2/C0, MAX/(C2/C0)); }

        public long toMicros(long d)  { return x(d, C2/C1, MAX/(C2/C1)); }

        public long toMillis(long d)  { return d; }

        public long toSeconds(long d) { return d/(C3/C2); }

        public long toMinutes(long d) { return d/(C4/C2); }

        public long toHours(long d)   { return d/(C5/C2); }

        public long toDays(long d)    { return d/(C6/C2); }

        public long convert(long d, TimeUnit u) { return u.toMillis(d); }

        int excessNanos(long d, long m) { return 0; }

    },

    SECONDS {

        public long toNanos(long d)   { return x(d, C3/C0, MAX/(C3/C0)); }

        public long toMicros(long d)  { return x(d, C3/C1, MAX/(C3/C1)); }

        public long toMillis(long d)  { return x(d, C3/C2, MAX/(C3/C2)); }

        public long toSeconds(long d) { return d; }

        public long toMinutes(long d) { return d/(C4/C3); }

        public long toHours(long d)   { return d/(C5/C3); }

        public long toDays(long d)    { return d/(C6/C3); }

        public long convert(long d, TimeUnit u) { return u.toSeconds(d); }

        int excessNanos(long d, long m) { return 0; }

    },

    MINUTES {

        public long toNanos(long d)   { return x(d, C4/C0, MAX/(C4/C0)); }

        public long toMicros(long d)  { return x(d, C4/C1, MAX/(C4/C1)); }

        public long toMillis(long d)  { return x(d, C4/C2, MAX/(C4/C2)); }

        public long toSeconds(long d) { return x(d, C4/C3, MAX/(C4/C3)); }

        public long toMinutes(long d) { return d; }

        public long toHours(long d)   { return d/(C5/C4); }

        public long toDays(long d)    { return d/(C6/C4); }

        public long convert(long d, TimeUnit u) { return u.toMinutes(d); }

        int excessNanos(long d, long m) { return 0; }

    },

    HOURS {

        public long toNanos(long d)   { return x(d, C5/C0, MAX/(C5/C0)); }

        public long toMicros(long d)  { return x(d, C5/C1, MAX/(C5/C1)); }

        public long toMillis(long d)  { return x(d, C5/C2, MAX/(C5/C2)); }

        public long toSeconds(long d) { return x(d, C5/C3, MAX/(C5/C3)); }

        public long toMinutes(long d) { return x(d, C5/C4, MAX/(C5/C4)); }

        public long toHours(long d)   { return d; }

        public long toDays(long d)    { return d/(C6/C5); }

        public long convert(long d, TimeUnit u) { return u.toHours(d); }

        int excessNanos(long d, long m) { return 0; }

    },

    DAYS {

        public long toNanos(long d)   { return x(d, C6/C0, MAX/(C6/C0)); }

        public long toMicros(long d)  { return x(d, C6/C1, MAX/(C6/C1)); }

        public long toMillis(long d)  { return x(d, C6/C2, MAX/(C6/C2)); }

        public long toSeconds(long d) { return x(d, C6/C3, MAX/(C6/C3)); }

        public long toMinutes(long d) { return x(d, C6/C4, MAX/(C6/C4)); }

        public long toHours(long d)   { return x(d, C6/C5, MAX/(C6/C5)); }

        public long toDays(long d)    { return d; }

        public long convert(long d, TimeUnit u) { return u.toDays(d); }

        int excessNanos(long d, long m) { return 0; }

    };

    // Handy constants for conversion methods

    static final long C0 = 1L;

    static final long C1 = C0 * 1000L;

    static final long C2 = C1 * 1000L;

    static final long C3 = C2 * 1000L;

    static final long C4 = C3 * 60L;

    static final long C5 = C4 * 60L;

    static final long C6 = C5 * 24L;

    static final long MAX = Long.MAX_VALUE;

    /**

     * Scale d by m, checking for overflow.

     * This has a short name to make above code more readable.

     */

    static long x(long d, long m, long over) {

        if (d >  over) return Long.MAX_VALUE;

        if (d < -over) return Long.MIN_VALUE;

        return d * m;

    }

    // To maintain full signature compatibility with 1.5, and to improve the

    // clarity of the generated javadoc (see 6287639: Abstract methods in

    // enum classes should not be listed as abstract), method convert

    // etc. are not declared abstract but otherwise act as abstract methods.

    /**

     * Convert the given time duration in the given unit to this

     * unit.  Conversions from finer to coarser granularities

     * truncate, so lose precision. For example converting

     * <tt>999</tt> milliseconds to seconds results in

     * <tt>0</tt>. Conversions from coarser to finer granularities

     * with arguments that would numerically overflow saturate to

     * <tt>Long.MIN_VALUE</tt> if negative or <tt>Long.MAX_VALUE</tt>

     * if positive.

     *

     * <p>For example, to convert 10 minutes to milliseconds, use:

     * <tt>TimeUnit.MILLISECONDS.convert(10L, TimeUnit.MINUTES)</tt>

     *

     * @param sourceDuration the time duration in the given <tt>sourceUnit</tt>

     * @param sourceUnit the unit of the <tt>sourceDuration</tt> argument

     * @return the converted duration in this unit,

     * or <tt>Long.MIN_VALUE</tt> if conversion would negatively

     * overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.

     */

    public long convert(long sourceDuration, TimeUnit sourceUnit) {

        throw new AbstractMethodError();

    }

    /**

     * Equivalent to <tt>NANOSECONDS.convert(duration, this)</tt>.

     * @param duration the duration

     * @return the converted duration,

     * or <tt>Long.MIN_VALUE</tt> if conversion would negatively

     * overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.

     * @see #convert

     */

    public long toNanos(long duration) {

        throw new AbstractMethodError();

    }

    /**

     * Equivalent to <tt>MICROSECONDS.convert(duration, this)</tt>.

     * @param duration the duration

     * @return the converted duration,

     * or <tt>Long.MIN_VALUE</tt> if conversion would negatively

     * overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.

     * @see #convert

     */

    public long toMicros(long duration) {

        throw new AbstractMethodError();

    }

    /**

     * Equivalent to <tt>MILLISECONDS.convert(duration, this)</tt>.

     * @param duration the duration

     * @return the converted duration,

     * or <tt>Long.MIN_VALUE</tt> if conversion would negatively

     * overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.

     * @see #convert

     */

    public long toMillis(long duration) {

        throw new AbstractMethodError();

    }

    /**

     * Equivalent to <tt>SECONDS.convert(duration, this)</tt>.

     * @param duration the duration

     * @return the converted duration,

     * or <tt>Long.MIN_VALUE</tt> if conversion would negatively

     * overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.

     * @see #convert

     */

    public long toSeconds(long duration) {

        throw new AbstractMethodError();

    }

    /**

     * Equivalent to <tt>MINUTES.convert(duration, this)</tt>.

     * @param duration the duration

     * @return the converted duration,

     * or <tt>Long.MIN_VALUE</tt> if conversion would negatively

     * overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.

     * @see #convert

     * @since 1.6

     */

    public long toMinutes(long duration) {

        throw new AbstractMethodError();

    }

    /**

     * Equivalent to <tt>HOURS.convert(duration, this)</tt>.

     * @param duration the duration

     * @return the converted duration,

     * or <tt>Long.MIN_VALUE</tt> if conversion would negatively

     * overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.

     * @see #convert

     * @since 1.6

     */

    public long toHours(long duration) {

        throw new AbstractMethodError();

    }

    /**

     * Equivalent to <tt>DAYS.convert(duration, this)</tt>.

     * @param duration the duration

     * @return the converted duration

     * @see #convert

     * @since 1.6

     */

    public long toDays(long duration) {

        throw new AbstractMethodError();

    }

    /**

     * Utility to compute the excess-nanosecond argument to wait,

     * sleep, join.

     * @param d the duration

     * @param m the number of milliseconds

     * @return the number of nanoseconds

     */

    abstract int excessNanos(long d, long m);

    /**

     * Performs a timed <tt>Object.wait</tt> using this time unit.

     * This is a convenience method that converts timeout arguments

     * into the form required by the <tt>Object.wait</tt> method.

     *

     * <p>For example, you could implement a blocking <tt>poll</tt>

     * method (see {@link BlockingQueue#poll BlockingQueue.poll})

     * using:

     *

     * <pre>  public synchronized Object poll(long timeout, TimeUnit unit) throws InterruptedException {

     *    while (empty) {

     *      unit.timedWait(this, timeout);

     *      ...

     *    }

     *  }</pre>

     *

     * @param obj the object to wait on

     * @param timeout the maximum time to wait. If less than

     * or equal to zero, do not wait at all.

     * @throws InterruptedException if interrupted while waiting.

     * @see Object#wait(long, int)

     */

    public void timedWait(Object obj, long timeout)

    throws InterruptedException {

        if (timeout > 0) {

            long ms = toMillis(timeout);

            int ns = excessNanos(timeout, ms);

            obj.wait(ms, ns);

        }

    }

    /**

     * Performs a timed <tt>Thread.join</tt> using this time unit.

     * This is a convenience method that converts time arguments into the

     * form required by the <tt>Thread.join</tt> method.

     * @param thread the thread to wait for

     * @param timeout the maximum time to wait. If less than

     * or equal to zero, do not wait at all.

     * @throws InterruptedException if interrupted while waiting.

     * @see Thread#join(long, int)

     */

    public void timedJoin(Thread thread, long timeout)

    throws InterruptedException {

        if (timeout > 0) {

            long ms = toMillis(timeout);

            int ns = excessNanos(timeout, ms);

            thread.join(ms, ns);

        }

    }

    /**

     * Performs a <tt>Thread.sleep</tt> using this unit.

     * This is a convenience method that converts time arguments into the

     * form required by the <tt>Thread.sleep</tt> method.

     * @param timeout the minimum time to sleep. If less than

     * or equal to zero, do not sleep at all.

     * @throws InterruptedException if interrupted while sleeping.

     * @see Thread#sleep

     */

    public void sleep(long timeout) throws InterruptedException {

        if (timeout > 0) {

            long ms = toMillis(timeout);

            int ns = excessNanos(timeout, ms);

            Thread.sleep(ms, ns);

        }

    }

}