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 {

    /**
     * Perform the conversion based on given index 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;
    }


    /**
     * Returns true if the given object is a TimeUnit representing
     * the same unit as this TimeUnit.
     * @param x the object to compare
     * @return true if equal
     */
    public boolean equals(Object x) {
        if (!(x instanceof TimeUnit))
            return false;
        return ((TimeUnit)x).index == index;
    }

    /**
     * Returns a hash code for this TimeUnit.
     * @return the hash code
     */
    public int hashCode() {
        return unitName.hashCode();
    }

    private final String unitName;

    /* 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 */
    static final int[] multipliers = { 1, 
                                       1000, 
                                       1000*1000, 
                                       1000*1000*1000 };

    /** lookup table to check saturation */
    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 */
    int index;

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

    /**
     * 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;
    }

    /** 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");

}
Revision:	1.13
Committed:	Fri Sep 12 15:40:10 2003 UTC (20 years, 8 months ago) by dl
Branch:	MAIN
Changes since 1.12:	+85 -23 lines
Log Message:	Adapt AbstractQueue changes; Conditionalize CancellableTask.reset; new TimeUnit methods
#	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
45			/**
46	dl	1.13	* Perform the conversion based on given index representing the
47			* difference between units
48			* @param delta the difference in index values of source and target units
49			* @param duration the duration
50			* @return converted duration or saturated value
51			*/
52			private static long doConvert(int delta, long duration) {
53			if (delta == 0)
54			return duration;
55			if (delta < 0)
56			return duration / multipliers[-delta];
57			if (duration > overflows[delta])
58			return Long.MAX_VALUE;
59			if (duration < -overflows[delta])
60			return Long.MIN_VALUE;
61			return duration * multipliers[delta];
62			}
63
64			/**
65	tim	1.1	* Convert the given time duration in the given unit to the
66			* current unit. Conversions from finer to coarser granulaties
67	dl	1.13	* truncate, so lose precision. For example converting
68			* <tt>999</tt> milliseconds to seconds results in
69			* <tt>0</tt>. Conversions from coarser to finer granularities
70			* with arguments that would numerically overflow saturate to
71			* <tt>Long.MIN_VALUE</tt> if negative or <tt>Long.MAX_VALUE</tt>
72			* if positive.
73	tim	1.1	*
74			* @param duration the time duration in the given <tt>unit</tt>
75			* @param unit the unit of the <tt>duration</tt> argument
76	dl	1.10	* @return the converted duration in the current unit,
77			* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
78	dl	1.11	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
79	tim	1.1	*/
80			public long convert(long duration, TimeUnit unit) {
81	dl	1.13	return doConvert(unit.index - index, duration);
82	dl	1.2	}
83
84			/**
85	dl	1.12	* Equivalent to <tt>NANOSECONDS.convert(duration, this)</tt>.
86	dl	1.2	* @param duration the duration
87	dl	1.13	* @return the converted duration,
88	dl	1.10	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
89	dl	1.11	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
90	dl	1.13	* @see #convert
91			*/
92	dl	1.2	public long toNanos(long duration) {
93	dl	1.13	return doConvert(index, duration);
94			}
95
96			/**
97			* Equivalent to <tt>MICROSECONDS.convert(duration, this)</tt>.
98			* @param duration the duration
99			* @return the converted duration,
100			* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
101			* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
102			* @see #convert
103			*/
104			public long toMicros(long duration) {
105			return doConvert(index - US, duration);
106			}
107
108			/**
109			* Equivalent to <tt>MILLISECONDS.convert(duration, this)</tt>.
110			* @param duration the duration
111			* @return the converted duration,
112			* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
113			* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
114			* @see #convert
115			*/
116			public long toMillis(long duration) {
117			return doConvert(index - MS, duration);
118			}
119
120			/**
121			* Equivalent to <tt>SECONDS.convert(duration, this)</tt>.
122			* @param duration the duration
123			* @return the converted duration.
124			* @see #convert
125			*/
126			public long toSeconds(long duration) {
127			return doConvert(index - S, duration);
128	tim	1.1	}
129	tim	1.6
130	tim	1.1	/**
131	tim	1.6	* Perform a timed <tt>Object.wait</tt> using the current time unit.
132	tim	1.1	* This is a convenience method that converts timeout arguments into the
133	dl	1.7	* form required by the <tt>Object.wait</tt> method.
134	tim	1.1	* <p>For example, you could implement a blocking <tt>poll</tt> method (see
135			* {@link BlockingQueue#poll BlockingQueue.poll} using:
136			* <pre> public synchronized Object poll(long timeout, TimeUnit unit) throws InterruptedException {
137			* while (empty) {
138			* unit.timedWait(this, timeout);
139			* ...
140			* }
141			* }</pre>
142			* @param obj the object to wait on
143	dl	1.10	* @param timeout the maximum time to wait.
144	tim	1.1	* @throws InterruptedException if interrupted while waiting.
145			* @see Object#wait(long, int)
146			*/
147			public void timedWait(Object obj, long timeout)
148			throws InterruptedException {
149	dl	1.10	if (timeout > 0) {
150			long ms = MILLISECONDS.convert(timeout, this);
151			int ns = excessNanos(timeout, ms);
152			obj.wait(ms, ns);
153			}
154	tim	1.1	}
155
156			/**
157			* Perform a timed <tt>Thread.join</tt> using the current time unit.
158			* This is a convenience method that converts time arguments into the
159			* form required by the <tt>Thread.join</tt> method.
160			* @param thread the thread to wait for
161			* @param timeout the maximum time to wait
162			* @throws InterruptedException if interrupted while waiting.
163			* @see Thread#join(long, int)
164			*/
165			public void timedJoin(Thread thread, long timeout)
166			throws InterruptedException {
167	dl	1.10	if (timeout > 0) {
168			long ms = MILLISECONDS.convert(timeout, this);
169			int ns = excessNanos(timeout, ms);
170			thread.join(ms, ns);
171			}
172	tim	1.1	}
173	tim	1.6
174	tim	1.1	/**
175			* Perform a <tt>Thread.sleep</tt> using the current time unit.
176			* This is a convenience method that converts time arguments into the
177			* form required by the <tt>Thread.sleep</tt> method.
178	tim	1.6	* @param timeout the minimum time to sleep
179	tim	1.1	* @throws InterruptedException if interrupted while sleeping.
180			* @see Thread#sleep
181			*/
182			public void sleep(long timeout) throws InterruptedException {
183	dl	1.10	if (timeout > 0) {
184			long ms = MILLISECONDS.convert(timeout, this);
185			int ns = excessNanos(timeout, ms);
186			Thread.sleep(ms, ns);
187			}
188	tim	1.1	}
189
190	dl	1.9	/**
191			* Return the common name for this unit.
192			*/
193			public String toString() {
194			return unitName;
195	dl	1.13	}
196
197
198			/**
199			* Returns true if the given object is a TimeUnit representing
200			* the same unit as this TimeUnit.
201			* @param x the object to compare
202			* @return true if equal
203			*/
204			public boolean equals(Object x) {
205			if (!(x instanceof TimeUnit))
206			return false;
207			return ((TimeUnit)x).index == index;
208			}
209
210			/**
211			* Returns a hash code for this TimeUnit.
212			* @return the hash code
213			*/
214			public int hashCode() {
215			return unitName.hashCode();
216	dl	1.9	}
217
218			private final String unitName;
219
220	tim	1.1	/* ordered indices for each time unit */
221			private static final int NS = 0;
222			private static final int US = 1;
223			private static final int MS = 2;
224			private static final int S = 3;
225
226	dl	1.4	/** quick lookup table for conversion factors */
227	dl	1.10	static final int[] multipliers = { 1,
228			1000,
229			1000*1000,
230			100010001000 };
231
232			/** lookup table to check saturation */
233			static final long[] overflows = {
234			// Note that because we are dividing these down anyway,
235			// we don't have to deal with asymmetry of MIN/MAX values.
236			0, // unused
237			Long.MAX_VALUE / 1000,
238			Long.MAX_VALUE / (1000 * 1000),
239			Long.MAX_VALUE / (1000 * 1000 * 1000) };
240	tim	1.1
241	dl	1.4	/** the index of this unit */
242	tim	1.1	int index;
243
244			/** private constructor */
245	dl	1.9	TimeUnit(int index, String name) {
246			this.index = index;
247			this.unitName = name;
248			}
249	tim	1.1
250	tim	1.6	/**
251	tim	1.1	* Utility method to compute the excess-nanosecond argument to
252	dl	1.7	* wait, sleep, join. The results may overflow, so public methods
253			* invoking this should document possible overflow unless
254			* overflow is known not to be possible for the given arguments.
255	tim	1.1	*/
256			private int excessNanos(long time, long ms) {
257	tim	1.6	if (index == NS)
258	tim	1.1	return (int) (time - (ms * multipliers[MS-NS]));
259	tim	1.6	else if (index == US)
260	tim	1.1	return (int) ((time * multipliers[US-NS]) - (ms * multipliers[MS-NS]));
261	tim	1.6	else
262	tim	1.1	return 0;
263			}
264
265	tim	1.8	/** Unit for one-second granularities. */
266	dl	1.9	public static final TimeUnit SECONDS = new TimeUnit(S, "seconds");
267	tim	1.1
268	tim	1.8	/** Unit for one-millisecond granularities. */
269	dl	1.9	public static final TimeUnit MILLISECONDS = new TimeUnit(MS, "milliseconds");
270	tim	1.1
271	tim	1.8	/** Unit for one-microsecond granularities. */
272	dl	1.9	public static final TimeUnit MICROSECONDS = new TimeUnit(US, "microseconds");
273	tim	1.1
274	tim	1.8	/** Unit for one-nanosecond granularities. */
275	dl	1.9	public static final TimeUnit NANOSECONDS = new TimeUnit(NS, "nanoseconds");
276	tim	1.1
277			}