util/concurrent/TimeUnit.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain. Use, modify, and
 * redistribute this code in any way without acknowledgement.
 */

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.
 * <tt>TimeUnit</tt> is a &quot;featherweight&quot; class.
 * It does not maintain time information, but only helps organize and
 * use time representations that may be maintained separately across
 * various contexts.
 *
 * <p>This class cannot be directly instantiated.  Use the {@link
 * #SECONDS}, {@link #MILLISECONDS}, {@link #MICROSECONDS}, and {@link
 * #NANOSECONDS} static instances that provide predefined units of
 * precision. If you use these frequently, consider statically
 * importing this class.
 *
 * <p>A <tt>TimeUnit</tt> is mainly used to inform blocking methods which
 * can timeout, how the timeout 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 lock, in this
 * case, 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 final class TimeUnit implements java.io.Serializable {
    /* ordered indices for each time unit */
    private static final int NS = 0;
    private static final int US = 1;
    private static final int MS = 2;
    private static final int S  = 3;

    /** quick lookup table for conversion factors */
    private static final int[] multipliers = { 1, 
                                       1000, 
                                       1000*1000, 
                                       1000*1000*1000 };

    /** lookup table to check saturation */
    private static final long[] overflows = { 
        // Note that because we are dividing these down anyway, 
        // we don't have to deal with asymmetry of MIN/MAX values.
        0, // unused
        Long.MAX_VALUE / 1000,
        Long.MAX_VALUE / (1000 * 1000),
        Long.MAX_VALUE / (1000 * 1000 * 1000) };

    /** the index of this unit */
    private int index;
    /** Common name for unit */
    private final String unitName;

    /** private constructor */
    TimeUnit(int index, String name) { 
        this.index = index; 
        this.unitName = name;
    }

    /** Unit for one-second granularities. */
    public static final TimeUnit SECONDS = new TimeUnit(S, "seconds");
    /** Unit for one-millisecond granularities. */
    public static final TimeUnit MILLISECONDS = new TimeUnit(MS, "milliseconds");
    /** Unit for one-microsecond granularities. */
    public static final TimeUnit MICROSECONDS = new TimeUnit(US, "microseconds");
    /** Unit for one-nanosecond granularities. */
    public static final TimeUnit NANOSECONDS = new TimeUnit(NS, "nanoseconds");

    /**
     * Utility method to compute the excess-nanosecond argument to
     * wait, sleep, join. The results may overflow, so public methods
     * invoking this should document possible overflow unless
     * overflow is known not to be possible for the given arguments.
     */
    private int excessNanos(long time, long ms) {
        if (index == NS)
            return (int) (time  - (ms * multipliers[MS-NS]));
        else if (index == US)
            return (int) ((time * multipliers[US-NS]) - (ms * multipliers[MS-NS]));
        else
            return 0;
    }

    /**
     * Perform conversion based on given delta representing the
     * difference between units
     * @param delta the difference in index values of source and target units
     * @param duration the duration
     * @return converted duration or saturated value
     */
    private static long doConvert(int delta, long duration) {
        if (delta == 0)
            return duration;
        if (delta < 0) 
            return duration / multipliers[-delta];
        if (duration > overflows[delta])
            return Long.MAX_VALUE;
        if (duration < -overflows[delta])
            return Long.MIN_VALUE;
        return duration * multipliers[delta];
    }

    /**
     * Convert the given time duration in the given unit to the
     * current unit.  Conversions from finer to coarser granulaties
     * 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.
     *
     * @param duration the time duration in the given <tt>unit</tt>
     * @param unit the unit of the <tt>duration</tt> argument
     * @return the converted duration in the current 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 duration, TimeUnit unit) {
        return doConvert(unit.index - index, duration);
    }

    /**
     * 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) {
        return doConvert(index, duration);
    }

    /**
     * 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) {
        return doConvert(index - US, duration);
    }

    /**
     * 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) {
        return doConvert(index - MS, duration);
    }

    /**
     * Equivalent to <tt>SECONDS.convert(duration, this)</tt>.
     * @param duration the duration
     * @return the converted duration.
     * @see #convert
     */
    public long toSeconds(long duration) {
        return doConvert(index - S, duration);
    }

    /**
     * Perform a timed <tt>Object.wait</tt> using the current 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. 
     * @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 = MILLISECONDS.convert(timeout, this);
            int ns = excessNanos(timeout, ms);
            obj.wait(ms, ns);
        }
    }

    /**
     * Perform a timed <tt>Thread.join</tt> using the current 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
     * @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 = MILLISECONDS.convert(timeout, this);
            int ns = excessNanos(timeout, ms);
            thread.join(ms, ns);
        }
    }

    /**
     * Perform a <tt>Thread.sleep</tt> using the current time 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
     * @throws InterruptedException if interrupted while sleeping.
     * @see Thread#sleep
     */
    public void sleep(long timeout) throws InterruptedException {
        if (timeout > 0) {
            long ms = MILLISECONDS.convert(timeout, this);
            int ns = excessNanos(timeout, ms);
            Thread.sleep(ms, ns);
        }
    }

    /**
     * Return the common name for this unit.
     */
    public String toString() {
        return unitName;
    }

    /**
     * Resolves instances being deserialized to a single instance per
     * unit.
     */
    private Object readResolve() {
        switch(index) {
        case NS: return NANOSECONDS;
        case US: return MICROSECONDS;
        case MS: return MILLISECONDS;
        case  S: return SECONDS;
        default: assert(false); return null;
        }
    }
}
Revision:	1.14
Committed:	Fri Sep 12 20:17:50 2003 UTC (20 years, 8 months ago) by dl
Branch:	MAIN
Changes since 1.13:	+66 -78 lines
Log Message:	Use readResolve to deserialize
#	User	Rev	Content
1	dl	1.2	/*
2			* Written by Doug Lea with assistance from members of JCP JSR-166
3			* Expert Group and released to the public domain. Use, modify, and
4			* redistribute this code in any way without acknowledgement.
5			*/
6
7	tim	1.1	package java.util.concurrent;
8
9			/**
10	tim	1.6	* A <tt>TimeUnit</tt> represents time durations at a given unit of
11			* granularity and provides utility methods to convert across units,
12			* and to perform timing and delay operations in these units.
13			* <tt>TimeUnit</tt> is a "featherweight" class.
14			* It does not maintain time information, but only helps organize and
15			* use time representations that may be maintained separately across
16	tim	1.1	* various contexts.
17			*
18	dl	1.12	* <p>This class cannot be directly instantiated. Use the {@link
19			* #SECONDS}, {@link #MILLISECONDS}, {@link #MICROSECONDS}, and {@link
20			* #NANOSECONDS} static instances that provide predefined units of
21			* precision. If you use these frequently, consider statically
22			* importing this class.
23	tim	1.1	*
24			* <p>A <tt>TimeUnit</tt> is mainly used to inform blocking methods which
25			* can timeout, how the timeout parameter should be interpreted. For example,
26	tim	1.6	* the following code will timeout in 50 milliseconds if the {@link java.util.concurrent.locks.Lock lock}
27	tim	1.1	* is not available:
28			* <pre> Lock lock = ...;
29			* if ( lock.tryLock(50L, TimeUnit.MILLISECONDS) ) ...
30			* </pre>
31			* while this code will timeout in 50 seconds:
32	tim	1.6	* <pre>
33	tim	1.1	* Lock lock = ...;
34			* if ( lock.tryLock(50L, TimeUnit.SECONDS) ) ...
35			* </pre>
36			* Note however, that there is no guarantee that a particular lock, in this
37			* case, will be able to notice the passage of time at the same granularity
38			* as the given <tt>TimeUnit</tt>.
39			*
40			* @since 1.5
41	dl	1.4	* @author Doug Lea
42	tim	1.1	*/
43			public final class TimeUnit implements java.io.Serializable {
44	dl	1.14	/* ordered indices for each time unit */
45			private static final int NS = 0;
46			private static final int US = 1;
47			private static final int MS = 2;
48			private static final int S = 3;
49
50			/** quick lookup table for conversion factors */
51			private static final int[] multipliers = { 1,
52			1000,
53			1000*1000,
54			100010001000 };
55
56			/** lookup table to check saturation */
57			private static final long[] overflows = {
58			// Note that because we are dividing these down anyway,
59			// we don't have to deal with asymmetry of MIN/MAX values.
60			0, // unused
61			Long.MAX_VALUE / 1000,
62			Long.MAX_VALUE / (1000 * 1000),
63			Long.MAX_VALUE / (1000 * 1000 * 1000) };
64
65			/** the index of this unit */
66			private int index;
67			/** Common name for unit */
68			private final String unitName;
69
70			/** private constructor */
71			TimeUnit(int index, String name) {
72			this.index = index;
73			this.unitName = name;
74			}
75
76			/** Unit for one-second granularities. */
77			public static final TimeUnit SECONDS = new TimeUnit(S, "seconds");
78			/** Unit for one-millisecond granularities. */
79			public static final TimeUnit MILLISECONDS = new TimeUnit(MS, "milliseconds");
80			/** Unit for one-microsecond granularities. */
81			public static final TimeUnit MICROSECONDS = new TimeUnit(US, "microseconds");
82			/** Unit for one-nanosecond granularities. */
83			public static final TimeUnit NANOSECONDS = new TimeUnit(NS, "nanoseconds");
84
85			/**
86			* Utility method to compute the excess-nanosecond argument to
87			* wait, sleep, join. The results may overflow, so public methods
88			* invoking this should document possible overflow unless
89			* overflow is known not to be possible for the given arguments.
90			*/
91			private int excessNanos(long time, long ms) {
92			if (index == NS)
93			return (int) (time - (ms * multipliers[MS-NS]));
94			else if (index == US)
95			return (int) ((time * multipliers[US-NS]) - (ms * multipliers[MS-NS]));
96			else
97			return 0;
98			}
99	tim	1.1
100			/**
101	dl	1.14	* Perform conversion based on given delta representing the
102	dl	1.13	* difference between units
103			* @param delta the difference in index values of source and target units
104			* @param duration the duration
105			* @return converted duration or saturated value
106			*/
107			private static long doConvert(int delta, long duration) {
108			if (delta == 0)
109			return duration;
110			if (delta < 0)
111			return duration / multipliers[-delta];
112			if (duration > overflows[delta])
113			return Long.MAX_VALUE;
114			if (duration < -overflows[delta])
115			return Long.MIN_VALUE;
116			return duration * multipliers[delta];
117			}
118
119			/**
120	tim	1.1	* Convert the given time duration in the given unit to the
121			* current unit. Conversions from finer to coarser granulaties
122	dl	1.13	* truncate, so lose precision. For example converting
123			* <tt>999</tt> milliseconds to seconds results in
124			* <tt>0</tt>. Conversions from coarser to finer granularities
125			* with arguments that would numerically overflow saturate to
126			* <tt>Long.MIN_VALUE</tt> if negative or <tt>Long.MAX_VALUE</tt>
127			* if positive.
128	tim	1.1	*
129			* @param duration the time duration in the given <tt>unit</tt>
130			* @param unit the unit of the <tt>duration</tt> argument
131	dl	1.10	* @return the converted duration in the current unit,
132			* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
133	dl	1.11	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
134	tim	1.1	*/
135			public long convert(long duration, TimeUnit unit) {
136	dl	1.13	return doConvert(unit.index - index, duration);
137	dl	1.2	}
138
139			/**
140	dl	1.12	* Equivalent to <tt>NANOSECONDS.convert(duration, this)</tt>.
141	dl	1.2	* @param duration the duration
142	dl	1.13	* @return the converted duration,
143	dl	1.10	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
144	dl	1.11	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
145	dl	1.13	* @see #convert
146			*/
147	dl	1.2	public long toNanos(long duration) {
148	dl	1.13	return doConvert(index, duration);
149			}
150
151			/**
152			* Equivalent to <tt>MICROSECONDS.convert(duration, this)</tt>.
153			* @param duration the duration
154			* @return the converted duration,
155			* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
156			* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
157			* @see #convert
158			*/
159			public long toMicros(long duration) {
160			return doConvert(index - US, duration);
161			}
162
163			/**
164			* Equivalent to <tt>MILLISECONDS.convert(duration, this)</tt>.
165			* @param duration the duration
166			* @return the converted duration,
167			* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
168			* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
169			* @see #convert
170			*/
171			public long toMillis(long duration) {
172			return doConvert(index - MS, duration);
173			}
174
175			/**
176			* Equivalent to <tt>SECONDS.convert(duration, this)</tt>.
177			* @param duration the duration
178			* @return the converted duration.
179			* @see #convert
180			*/
181			public long toSeconds(long duration) {
182			return doConvert(index - S, duration);
183	tim	1.1	}
184	tim	1.6
185	tim	1.1	/**
186	tim	1.6	* Perform a timed <tt>Object.wait</tt> using the current time unit.
187	tim	1.1	* This is a convenience method that converts timeout arguments into the
188	dl	1.7	* form required by the <tt>Object.wait</tt> method.
189	tim	1.1	* <p>For example, you could implement a blocking <tt>poll</tt> method (see
190			* {@link BlockingQueue#poll BlockingQueue.poll} using:
191			* <pre> public synchronized Object poll(long timeout, TimeUnit unit) throws InterruptedException {
192			* while (empty) {
193			* unit.timedWait(this, timeout);
194			* ...
195			* }
196			* }</pre>
197			* @param obj the object to wait on
198	dl	1.10	* @param timeout the maximum time to wait.
199	tim	1.1	* @throws InterruptedException if interrupted while waiting.
200			* @see Object#wait(long, int)
201			*/
202			public void timedWait(Object obj, long timeout)
203			throws InterruptedException {
204	dl	1.10	if (timeout > 0) {
205			long ms = MILLISECONDS.convert(timeout, this);
206			int ns = excessNanos(timeout, ms);
207			obj.wait(ms, ns);
208			}
209	tim	1.1	}
210
211			/**
212			* Perform a timed <tt>Thread.join</tt> using the current time unit.
213			* This is a convenience method that converts time arguments into the
214			* form required by the <tt>Thread.join</tt> method.
215			* @param thread the thread to wait for
216			* @param timeout the maximum time to wait
217			* @throws InterruptedException if interrupted while waiting.
218			* @see Thread#join(long, int)
219			*/
220			public void timedJoin(Thread thread, long timeout)
221			throws InterruptedException {
222	dl	1.10	if (timeout > 0) {
223			long ms = MILLISECONDS.convert(timeout, this);
224			int ns = excessNanos(timeout, ms);
225			thread.join(ms, ns);
226			}
227	tim	1.1	}
228	tim	1.6
229	tim	1.1	/**
230			* Perform a <tt>Thread.sleep</tt> using the current time unit.
231			* This is a convenience method that converts time arguments into the
232			* form required by the <tt>Thread.sleep</tt> method.
233	tim	1.6	* @param timeout the minimum time to sleep
234	tim	1.1	* @throws InterruptedException if interrupted while sleeping.
235			* @see Thread#sleep
236			*/
237			public void sleep(long timeout) throws InterruptedException {
238	dl	1.10	if (timeout > 0) {
239			long ms = MILLISECONDS.convert(timeout, this);
240			int ns = excessNanos(timeout, ms);
241			Thread.sleep(ms, ns);
242			}
243	tim	1.1	}
244
245	dl	1.9	/**
246			* Return the common name for this unit.
247			*/
248			public String toString() {
249			return unitName;
250	dl	1.13	}
251
252			/**
253	dl	1.14	* Resolves instances being deserialized to a single instance per
254			* unit.
255	dl	1.13	*/
256	dl	1.14	private Object readResolve() {
257			switch(index) {
258			case NS: return NANOSECONDS;
259			case US: return MICROSECONDS;
260			case MS: return MILLISECONDS;
261			case S: return SECONDS;
262			default: assert(false); return null;
263			}
264	dl	1.9	}
265	tim	1.1	}