util/concurrent/TimeUnit.java

/*
 * 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.
 * <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 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 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.
     */
    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 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.
     *
     * @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 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 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 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. 
     * @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);
        }
    }

    /**
     * Perform 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
     * @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);
        }
    }

    /**
     * Perform 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
     * @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);
        }
    }

    /**
     * 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:	1.18
Committed:	Sat Dec 27 19:26:26 2003 UTC (20 years, 5 months ago) by dl
Branch:	MAIN
Changes since 1.17:	+2 -2 lines
Log Message:	Headers reference Creative Commons
#	User	Rev	Content
1	dl	1.2	/*
2			* Written by Doug Lea with assistance from members of JCP JSR-166
3	dl	1.18	* Expert Group and released to the public domain, as explained at
4			* http://creativecommons.org/licenses/publicdomain
5	dl	1.2	*/
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	dl	1.15	*
37			* Note however, that there is no guarantee that a particular timeout
38			* implementation will be able to notice the passage of time at the
39			* same granularity as the given <tt>TimeUnit</tt>.
40	tim	1.1	*
41			* @since 1.5
42	dl	1.4	* @author Doug Lea
43	tim	1.1	*/
44			public final class TimeUnit implements java.io.Serializable {
45	dl	1.14	/* ordered indices for each time unit */
46			private static final int NS = 0;
47			private static final int US = 1;
48			private static final int MS = 2;
49			private static final int S = 3;
50
51			/** quick lookup table for conversion factors */
52			private static final int[] multipliers = { 1,
53			1000,
54			1000*1000,
55			100010001000 };
56
57			/** lookup table to check saturation */
58			private static final long[] overflows = {
59			// Note that because we are dividing these down anyway,
60			// we don't have to deal with asymmetry of MIN/MAX values.
61			0, // unused
62			Long.MAX_VALUE / 1000,
63			Long.MAX_VALUE / (1000 * 1000),
64			Long.MAX_VALUE / (1000 * 1000 * 1000) };
65
66			/** the index of this unit */
67			private int index;
68			/** Common name for unit */
69			private final String unitName;
70
71			/** private constructor */
72			TimeUnit(int index, String name) {
73			this.index = index;
74			this.unitName = name;
75			}
76
77			/** Unit for one-second granularities. */
78			public static final TimeUnit SECONDS = new TimeUnit(S, "seconds");
79			/** Unit for one-millisecond granularities. */
80			public static final TimeUnit MILLISECONDS = new TimeUnit(MS, "milliseconds");
81			/** Unit for one-microsecond granularities. */
82			public static final TimeUnit MICROSECONDS = new TimeUnit(US, "microseconds");
83			/** Unit for one-nanosecond granularities. */
84			public static final TimeUnit NANOSECONDS = new TimeUnit(NS, "nanoseconds");
85
86			/**
87			* Utility method to compute the excess-nanosecond argument to
88	dl	1.15	* wait, sleep, join.
89	dl	1.14	*/
90			private int excessNanos(long time, long ms) {
91			if (index == NS)
92			return (int) (time - (ms * multipliers[MS-NS]));
93			else if (index == US)
94			return (int) ((time * multipliers[US-NS]) - (ms * multipliers[MS-NS]));
95			else
96			return 0;
97			}
98	tim	1.1
99			/**
100	dl	1.14	* Perform conversion based on given delta representing the
101	dl	1.13	* difference between units
102			* @param delta the difference in index values of source and target units
103			* @param duration the duration
104			* @return converted duration or saturated value
105			*/
106			private static long doConvert(int delta, long duration) {
107			if (delta == 0)
108			return duration;
109			if (delta < 0)
110			return duration / multipliers[-delta];
111			if (duration > overflows[delta])
112			return Long.MAX_VALUE;
113			if (duration < -overflows[delta])
114			return Long.MIN_VALUE;
115			return duration * multipliers[delta];
116			}
117
118			/**
119	dl	1.17	* Convert the given time duration in the given unit to this
120			* unit. Conversions from finer to coarser granularities
121	dl	1.13	* truncate, so lose precision. For example converting
122			* <tt>999</tt> milliseconds to seconds results in
123			* <tt>0</tt>. Conversions from coarser to finer granularities
124			* with arguments that would numerically overflow saturate to
125			* <tt>Long.MIN_VALUE</tt> if negative or <tt>Long.MAX_VALUE</tt>
126			* if positive.
127	tim	1.1	*
128			* @param duration the time duration in the given <tt>unit</tt>
129			* @param unit the unit of the <tt>duration</tt> argument
130	dl	1.17	* @return the converted duration in this unit,
131	dl	1.10	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
132	dl	1.11	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
133	tim	1.1	*/
134			public long convert(long duration, TimeUnit unit) {
135	dl	1.13	return doConvert(unit.index - index, duration);
136	dl	1.2	}
137
138			/**
139	dl	1.12	* Equivalent to <tt>NANOSECONDS.convert(duration, this)</tt>.
140	dl	1.2	* @param duration the duration
141	dl	1.13	* @return the converted duration,
142	dl	1.10	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
143	dl	1.11	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
144	dl	1.13	* @see #convert
145			*/
146	dl	1.2	public long toNanos(long duration) {
147	dl	1.13	return doConvert(index, duration);
148			}
149
150			/**
151			* Equivalent to <tt>MICROSECONDS.convert(duration, this)</tt>.
152			* @param duration the duration
153			* @return the converted duration,
154			* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
155			* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
156			* @see #convert
157			*/
158			public long toMicros(long duration) {
159			return doConvert(index - US, duration);
160			}
161
162			/**
163			* Equivalent to <tt>MILLISECONDS.convert(duration, this)</tt>.
164			* @param duration the duration
165			* @return the converted duration,
166			* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
167			* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
168			* @see #convert
169			*/
170			public long toMillis(long duration) {
171			return doConvert(index - MS, duration);
172			}
173
174			/**
175			* Equivalent to <tt>SECONDS.convert(duration, this)</tt>.
176			* @param duration the duration
177			* @return the converted duration.
178			* @see #convert
179			*/
180			public long toSeconds(long duration) {
181			return doConvert(index - S, duration);
182	tim	1.1	}
183	tim	1.6
184	tim	1.1	/**
185	dl	1.17	* Perform a timed <tt>Object.wait</tt> using this time unit.
186	tim	1.1	* This is a convenience method that converts timeout arguments into the
187	dl	1.7	* form required by the <tt>Object.wait</tt> method.
188	tim	1.1	* <p>For example, you could implement a blocking <tt>poll</tt> method (see
189			* {@link BlockingQueue#poll BlockingQueue.poll} using:
190			* <pre> public synchronized Object poll(long timeout, TimeUnit unit) throws InterruptedException {
191			* while (empty) {
192			* unit.timedWait(this, timeout);
193			* ...
194			* }
195			* }</pre>
196			* @param obj the object to wait on
197	dl	1.10	* @param timeout the maximum time to wait.
198	tim	1.1	* @throws InterruptedException if interrupted while waiting.
199			* @see Object#wait(long, int)
200			*/
201			public void timedWait(Object obj, long timeout)
202			throws InterruptedException {
203	dl	1.10	if (timeout > 0) {
204	dl	1.15	long ms = toMillis(timeout);
205	dl	1.10	int ns = excessNanos(timeout, ms);
206			obj.wait(ms, ns);
207			}
208	tim	1.1	}
209
210			/**
211	dl	1.17	* Perform a timed <tt>Thread.join</tt> using this time unit.
212	tim	1.1	* This is a convenience method that converts time arguments into the
213			* form required by the <tt>Thread.join</tt> method.
214			* @param thread the thread to wait for
215			* @param timeout the maximum time to wait
216			* @throws InterruptedException if interrupted while waiting.
217			* @see Thread#join(long, int)
218			*/
219			public void timedJoin(Thread thread, long timeout)
220			throws InterruptedException {
221	dl	1.10	if (timeout > 0) {
222	dl	1.15	long ms = toMillis(timeout);
223	dl	1.10	int ns = excessNanos(timeout, ms);
224			thread.join(ms, ns);
225			}
226	tim	1.1	}
227	tim	1.6
228	tim	1.1	/**
229	dl	1.17	* Perform a <tt>Thread.sleep</tt> using this unit.
230	tim	1.1	* This is a convenience method that converts time arguments into the
231			* form required by the <tt>Thread.sleep</tt> method.
232	tim	1.6	* @param timeout the minimum time to sleep
233	tim	1.1	* @throws InterruptedException if interrupted while sleeping.
234			* @see Thread#sleep
235			*/
236			public void sleep(long timeout) throws InterruptedException {
237	dl	1.10	if (timeout > 0) {
238	dl	1.15	long ms = toMillis(timeout);
239	dl	1.10	int ns = excessNanos(timeout, ms);
240			Thread.sleep(ms, ns);
241			}
242	tim	1.1	}
243
244	dl	1.9	/**
245			* Return the common name for this unit.
246			*/
247			public String toString() {
248			return unitName;
249	dl	1.13	}
250
251			/**
252	dl	1.14	* Resolves instances being deserialized to a single instance per
253			* unit.
254	dl	1.13	*/
255	dl	1.14	private Object readResolve() {
256			switch(index) {
257			case NS: return NANOSECONDS;
258			case US: return MICROSECONDS;
259			case MS: return MILLISECONDS;
260			case S: return SECONDS;
261			default: assert(false); return null;
262			}
263	dl	1.9	}
264	tim	1.1	}