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>The <tt>TimeUnit</tt> 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
 * @spec JSR-166
 * @revised $Date: 2003/08/07 16:00:28 $
 * @editor $Author: dl $
 * @author Doug Lea
 */
public final class TimeUnit implements java.io.Serializable {

    /**
     * Convert the given time duration in the given unit to the
     * current unit.  Conversions from finer to coarser granulaties
     * truncate, so lose precision. 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) {
        if (unit == this)
            return duration;
        else if (index > unit.index) 
            return duration / multipliers[index - unit.index];
        else {
            int i = unit.index - index;
            if (duration > overflows[i])
                return Long.MAX_VALUE;
            if (duration < -overflows[i])
                return Long.MIN_VALUE;
            return duration * multipliers[i];
        }
    }

    /**
     * Equivalent to <code>NANOSECONDS.convert(duration, this)</code>.
     * @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.
     **/
    public long toNanos(long duration) {
        if (index == NS)
            return duration;
        if (duration > overflows[index])
            return Long.MAX_VALUE;
        if (duration < -overflows[index])
            return Long.MIN_VALUE;
        return duration * multipliers[index];
    }

    /**
     * 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;
    }

    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:	1.10
Committed:	Sat Aug 30 14:52:52 2003 UTC (20 years, 9 months ago) by dl
Branch:	MAIN
Changes since 1.9:	+53 -20 lines
Log Message:	Saturate conversions
#	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>The <tt>TimeUnit</tt> class cannot be directly instantiated.
19	* Use the {@link #SECONDS}, {@link #MILLISECONDS}, {@link #MICROSECONDS},
20	* and {@link #NANOSECONDS} static instances that provide predefined
21	* units of precision. If you use these frequently, consider
22	* statically 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	* @spec JSR-166
42	* @revised $Date: 2003/08/07 16:00:28 $
43	* @editor $Author: dl $
44	* @author Doug Lea
45	*/
46	public final class TimeUnit implements java.io.Serializable {
47
48	/**
49	* Convert the given time duration in the given unit to the
50	* current unit. Conversions from finer to coarser granulaties
51	* truncate, so lose precision. Conversions from coarser to finer
52	* granularities with arguments that would numerically overflow
53	* saturate to <tt>Long.MIN_VALUE</tt> if negative or
54	* <tt>Long>MAX_VALUE</tt> if positive.
55	*
56	* @param duration the time duration in the given <tt>unit</tt>
57	* @param unit the unit of the <tt>duration</tt> argument
58	* @return the converted duration in the current unit,
59	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
60	* overflow, or <tt>Long>MAX_VALUE</tt> if it would positively overflow.
61	*/
62	public long convert(long duration, TimeUnit unit) {
63	if (unit == this)
64	return duration;
65	else if (index > unit.index)
66	return duration / multipliers[index - unit.index];
67	else {
68	int i = unit.index - index;
69	if (duration > overflows[i])
70	return Long.MAX_VALUE;
71	if (duration < -overflows[i])
72	return Long.MIN_VALUE;
73	return duration * multipliers[i];
74	}
75	}
76
77	/**
78	* Equivalent to <code>NANOSECONDS.convert(duration, this)</code>.
79	* @param duration the duration
80	* @return the converted duration.
81	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
82	* overflow, or <tt>Long>MAX_VALUE</tt> if it would positively overflow.
83	**/
84	public long toNanos(long duration) {
85	if (index == NS)
86	return duration;
87	if (duration > overflows[index])
88	return Long.MAX_VALUE;
89	if (duration < -overflows[index])
90	return Long.MIN_VALUE;
91	return duration * multipliers[index];
92	}
93
94	/**
95	* Perform a timed <tt>Object.wait</tt> using the current time unit.
96	* This is a convenience method that converts timeout arguments into the
97	* form required by the <tt>Object.wait</tt> method.
98	* <p>For example, you could implement a blocking <tt>poll</tt> method (see
99	* {@link BlockingQueue#poll BlockingQueue.poll} using:
100	* <pre> public synchronized Object poll(long timeout, TimeUnit unit) throws InterruptedException {
101	* while (empty) {
102	* unit.timedWait(this, timeout);
103	* ...
104	* }
105	* }</pre>
106	* @param obj the object to wait on
107	* @param timeout the maximum time to wait.
108	* @throws InterruptedException if interrupted while waiting.
109	* @see Object#wait(long, int)
110	*/
111	public void timedWait(Object obj, long timeout)
112	throws InterruptedException {
113	if (timeout > 0) {
114	long ms = MILLISECONDS.convert(timeout, this);
115	int ns = excessNanos(timeout, ms);
116	obj.wait(ms, ns);
117	}
118	}
119
120	/**
121	* Perform a timed <tt>Thread.join</tt> using the current time unit.
122	* This is a convenience method that converts time arguments into the
123	* form required by the <tt>Thread.join</tt> method.
124	* @param thread the thread to wait for
125	* @param timeout the maximum time to wait
126	* @throws InterruptedException if interrupted while waiting.
127	* @see Thread#join(long, int)
128	*/
129	public void timedJoin(Thread thread, long timeout)
130	throws InterruptedException {
131	if (timeout > 0) {
132	long ms = MILLISECONDS.convert(timeout, this);
133	int ns = excessNanos(timeout, ms);
134	thread.join(ms, ns);
135	}
136	}
137
138	/**
139	* Perform a <tt>Thread.sleep</tt> using the current time unit.
140	* This is a convenience method that converts time arguments into the
141	* form required by the <tt>Thread.sleep</tt> method.
142	* @param timeout the minimum time to sleep
143	* @throws InterruptedException if interrupted while sleeping.
144	* @see Thread#sleep
145	*/
146	public void sleep(long timeout) throws InterruptedException {
147	if (timeout > 0) {
148	long ms = MILLISECONDS.convert(timeout, this);
149	int ns = excessNanos(timeout, ms);
150	Thread.sleep(ms, ns);
151	}
152	}
153
154	/**
155	* Return the common name for this unit.
156	*/
157	public String toString() {
158	return unitName;
159	}
160
161	private final String unitName;
162
163	/* ordered indices for each time unit */
164	private static final int NS = 0;
165	private static final int US = 1;
166	private static final int MS = 2;
167	private static final int S = 3;
168
169	/** quick lookup table for conversion factors */
170	static final int[] multipliers = { 1,
171	1000,
172	1000*1000,
173	100010001000 };
174
175	/** lookup table to check saturation */
176	static final long[] overflows = {
177	// Note that because we are dividing these down anyway,
178	// we don't have to deal with asymmetry of MIN/MAX values.
179	0, // unused
180	Long.MAX_VALUE / 1000,
181	Long.MAX_VALUE / (1000 * 1000),
182	Long.MAX_VALUE / (1000 * 1000 * 1000) };
183
184	/** the index of this unit */
185	int index;
186
187	/** private constructor */
188	TimeUnit(int index, String name) {
189	this.index = index;
190	this.unitName = name;
191	}
192
193	/**
194	* Utility method to compute the excess-nanosecond argument to
195	* wait, sleep, join. The results may overflow, so public methods
196	* invoking this should document possible overflow unless
197	* overflow is known not to be possible for the given arguments.
198	*/
199	private int excessNanos(long time, long ms) {
200	if (index == NS)
201	return (int) (time - (ms * multipliers[MS-NS]));
202	else if (index == US)
203	return (int) ((time * multipliers[US-NS]) - (ms * multipliers[MS-NS]));
204	else
205	return 0;
206	}
207
208	/** Unit for one-second granularities. */
209	public static final TimeUnit SECONDS = new TimeUnit(S, "seconds");
210
211	/** Unit for one-millisecond granularities. */
212	public static final TimeUnit MILLISECONDS = new TimeUnit(MS, "milliseconds");
213
214	/** Unit for one-microsecond granularities. */
215	public static final TimeUnit MICROSECONDS = new TimeUnit(US, "microseconds");
216
217	/** Unit for one-nanosecond granularities. */
218	public static final TimeUnit NANOSECONDS = new TimeUnit(NS, "nanoseconds");
219
220	}