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
#	Content
1	/*
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	package java.util.concurrent;
8
9	/**
10	* 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	* various contexts.
17	*
18	* <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	*
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	* the following code will timeout in 50 milliseconds if the {@link java.util.concurrent.locks.Lock lock}
27	* 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	* <pre>
33	* 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	* @author Doug Lea
42	*/
43	public final class TimeUnit implements java.io.Serializable {
44
45	/**
46	* 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	* Convert the given time duration in the given unit to the
66	* current unit. Conversions from finer to coarser granulaties
67	* 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	*
74	* @param duration the time duration in the given <tt>unit</tt>
75	* @param unit the unit of the <tt>duration</tt> argument
76	* @return the converted duration in the current unit,
77	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
78	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
79	*/
80	public long convert(long duration, TimeUnit unit) {
81	return doConvert(unit.index - index, duration);
82	}
83
84	/**
85	* Equivalent to <tt>NANOSECONDS.convert(duration, this)</tt>.
86	* @param duration the duration
87	* @return the converted duration,
88	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
89	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
90	* @see #convert
91	*/
92	public long toNanos(long duration) {
93	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	}
129
130	/**
131	* Perform a timed <tt>Object.wait</tt> using the current time unit.
132	* This is a convenience method that converts timeout arguments into the
133	* form required by the <tt>Object.wait</tt> method.
134	* <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	* @param timeout the maximum time to wait.
144	* @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	if (timeout > 0) {
150	long ms = MILLISECONDS.convert(timeout, this);
151	int ns = excessNanos(timeout, ms);
152	obj.wait(ms, ns);
153	}
154	}
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	if (timeout > 0) {
168	long ms = MILLISECONDS.convert(timeout, this);
169	int ns = excessNanos(timeout, ms);
170	thread.join(ms, ns);
171	}
172	}
173
174	/**
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	* @param timeout the minimum time to sleep
179	* @throws InterruptedException if interrupted while sleeping.
180	* @see Thread#sleep
181	*/
182	public void sleep(long timeout) throws InterruptedException {
183	if (timeout > 0) {
184	long ms = MILLISECONDS.convert(timeout, this);
185	int ns = excessNanos(timeout, ms);
186	Thread.sleep(ms, ns);
187	}
188	}
189
190	/**
191	* Return the common name for this unit.
192	*/
193	public String toString() {
194	return unitName;
195	}
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	}
217
218	private final String unitName;
219
220	/* 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	/** quick lookup table for conversion factors */
227	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
241	/** the index of this unit */
242	int index;
243
244	/** private constructor */
245	TimeUnit(int index, String name) {
246	this.index = index;
247	this.unitName = name;
248	}
249
250	/**
251	* Utility method to compute the excess-nanosecond argument to
252	* 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	*/
256	private int excessNanos(long time, long ms) {
257	if (index == NS)
258	return (int) (time - (ms * multipliers[MS-NS]));
259	else if (index == US)
260	return (int) ((time * multipliers[US-NS]) - (ms * multipliers[MS-NS]));
261	else
262	return 0;
263	}
264
265	/** Unit for one-second granularities. */
266	public static final TimeUnit SECONDS = new TimeUnit(S, "seconds");
267
268	/** Unit for one-millisecond granularities. */
269	public static final TimeUnit MILLISECONDS = new TimeUnit(MS, "milliseconds");
270
271	/** Unit for one-microsecond granularities. */
272	public static final TimeUnit MICROSECONDS = new TimeUnit(US, "microseconds");
273
274	/** Unit for one-nanosecond granularities. */
275	public static final TimeUnit NANOSECONDS = new TimeUnit(NS, "nanoseconds");
276
277	}