util/concurrent/TimeUnit.java

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.
 * A static method {@link #highResolutionTime} provides access to a high
 * resolution, nanosecond, timer, which can be used to measure elapsed time.
 *
 * <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 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: 2003/03/29 02:17:05 $
 * @editor $Author: dholmes $
 *
 * @fixme The previous version created singleton subclass instances. I could
 * not see any reason to create subclasses instead of just instances.
 * Neither approach allows creation of your own units.
 */
public final class TimeUnit implements java.io.Serializable {

    /**
     * Return the current value of the system high resolution timer, in
     * nanoseconds. This method can only be used to measure elapsed time
     * and is not related to any notion of system, or wall-clock time.
     * Although the value returned represents nanoseconds since some
     * arbitrary start time in the past, the resolution at which this value
     * is updated is not specified. So we have nanosecond precision, but
     * not necessarily nanosecond accuracy.
     * It is guaranteed that successive return
     * values from this method will not decrease.
     *
     * <p> For example to measure how long some code takes to execute, 
     * with nanosecond precision:
     * <pre>
     * long startTime = TimeUnit.highResolutionTime();
     * // ... the code being measured ...
     * long estimatedTime = TimeUnit.highResolutionTime() - startTime;
     * </pre>
     * 
     * @return The current value of the system high resolution timer, in
     * nanoseconds.
     *
     * @fixme Is this spec tight enough? Too tight? What about issues of
     * reading the TSC from different processors on a SMP?
     */
    public static final long highResolutionTime() {
        return systemTimeNanos();
    }

    /**
     * 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 may numerically overflow.
     *
     * @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.
     */
    public long convert(long duration, TimeUnit unit) {
        if (index > unit.index) {
            return duration / multipliers[index - unit.index];
        }
        else {
            return duration * multipliers[unit.index - 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 {
        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 {
        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 time the minimum time to sleep 
     * @throws InterruptedException if interrupted while sleeping.
     * @see Thread#sleep
     */
    public void sleep(long timeout) throws InterruptedException {
        long ms = MILLISECONDS.convert(timeout, this);
        int ns = excessNanos(timeout, ms);
        Thread.sleep(ms, ns);
    }

    /* 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 };

    /* the index of this unit */
    int index;

    /** private constructor */
    TimeUnit(int index) { this.index = index; }

    /** 
     * Utility method to compute the excess-nanosecond argument to
     * wait, sleep, join.
     * @fixme overflow?
     */
    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;
    }

    /** Underlying native time call */
    static native long systemTimeNanos();

    /** Unit for one-second granularities */
    public static final TimeUnit SECONDS = new TimeUnit(S);

    /** Unit for one-millisecond granularities */
    public static final TimeUnit MILLISECONDS = new TimeUnit(MS);

    /** Unit for one-microsecond granularities */
    public static final TimeUnit MICROSECONDS = new TimeUnit(US);

    /** Unit for one-nanosecond granularities */
    public static final TimeUnit NANOSECONDS = new TimeUnit(NS);

}
Revision:	1.1
Committed:	Wed May 14 21:30:48 2003 UTC (21 years, 1 month ago) by tim
Branch:	MAIN
Log Message:	Moved main source rooted at . to ./src/main Moved test source rooted at ./etc/testcases to ./src/test
#	Content
1	package java.util.concurrent;
2
3	/**
4	* A <tt>TimeUnit</tt> represents time durations at a given unit of
5	* granularity and provides utility methods to convert across units,
6	* and to perform timing and delay operations in these units.
7	* <tt>TimeUnit</tt> is a "featherweight" class.
8	* It does not maintain time information, but only helps organize and
9	* use time representations that may be maintained separately across
10	* various contexts.
11	* A static method {@link #highResolutionTime} provides access to a high
12	* resolution, nanosecond, timer, which can be used to measure elapsed time.
13	*
14	* <p>The <tt>TimeUnit</tt> class cannot be directly instantiated.
15	* Use the {@link #SECONDS}, {@link #MILLISECONDS}, {@link #MICROSECONDS},
16	* and {@link #NANOSECONDS} static instances that provide predefined
17	* units of precision. If you use these frequently, consider
18	* statically importing this class.
19	*
20	* <p>A <tt>TimeUnit</tt> is mainly used to inform blocking methods which
21	* can timeout, how the timeout parameter should be interpreted. For example,
22	* the following code will timeout in 50 milliseconds if the {@link Lock lock}
23	* is not available:
24	* <pre> Lock lock = ...;
25	* if ( lock.tryLock(50L, TimeUnit.MILLISECONDS) ) ...
26	* </pre>
27	* while this code will timeout in 50 seconds:
28	* <pre>
29	* Lock lock = ...;
30	* if ( lock.tryLock(50L, TimeUnit.SECONDS) ) ...
31	* </pre>
32	* Note however, that there is no guarantee that a particular lock, in this
33	* case, will be able to notice the passage of time at the same granularity
34	* as the given <tt>TimeUnit</tt>.
35	*
36	* @since 1.5
37	* @spec JSR-166
38	* @revised $Date: 2003/03/29 02:17:05 $
39	* @editor $Author: dholmes $
40	*
41	* @fixme The previous version created singleton subclass instances. I could
42	* not see any reason to create subclasses instead of just instances.
43	* Neither approach allows creation of your own units.
44	*/
45	public final class TimeUnit implements java.io.Serializable {
46
47	/**
48	* Return the current value of the system high resolution timer, in
49	* nanoseconds. This method can only be used to measure elapsed time
50	* and is not related to any notion of system, or wall-clock time.
51	* Although the value returned represents nanoseconds since some
52	* arbitrary start time in the past, the resolution at which this value
53	* is updated is not specified. So we have nanosecond precision, but
54	* not necessarily nanosecond accuracy.
55	* It is guaranteed that successive return
56	* values from this method will not decrease.
57	*
58	* <p> For example to measure how long some code takes to execute,
59	* with nanosecond precision:
60	* <pre>
61	* long startTime = TimeUnit.highResolutionTime();
62	* // ... the code being measured ...
63	* long estimatedTime = TimeUnit.highResolutionTime() - startTime;
64	* </pre>
65	*
66	* @return The current value of the system high resolution timer, in
67	* nanoseconds.
68	*
69	* @fixme Is this spec tight enough? Too tight? What about issues of
70	* reading the TSC from different processors on a SMP?
71	*/
72	public static final long highResolutionTime() {
73	return systemTimeNanos();
74	}
75
76	/**
77	* Convert the given time duration in the given unit to the
78	* current unit. Conversions from finer to coarser granulaties
79	* truncate, so lose precision. Conversions from coarser to finer
80	* granularities may numerically overflow.
81	*
82	* @param duration the time duration in the given <tt>unit</tt>
83	* @param unit the unit of the <tt>duration</tt> argument
84	* @return the converted duration in the current unit.
85	*/
86	public long convert(long duration, TimeUnit unit) {
87	if (index > unit.index) {
88	return duration / multipliers[index - unit.index];
89	}
90	else {
91	return duration * multipliers[unit.index - index];
92	}
93	}
94
95	/**
96	* Perform a timed <tt>Object.wait</tt> using the current time unit.
97	* This is a convenience method that converts timeout arguments into the
98	* form required by the <tt>Object.wait</tt> method.
99	* <p>For example, you could implement a blocking <tt>poll</tt> method (see
100	* {@link BlockingQueue#poll BlockingQueue.poll} using:
101	* <pre> public synchronized Object poll(long timeout, TimeUnit unit) throws InterruptedException {
102	* while (empty) {
103	* unit.timedWait(this, timeout);
104	* ...
105	* }
106	* }</pre>
107	* @param obj the object to wait on
108	* @param timeout the maximum time to wait
109	* @throws InterruptedException if interrupted while waiting.
110	* @see Object#wait(long, int)
111	*/
112	public void timedWait(Object obj, long timeout)
113	throws InterruptedException {
114	long ms = MILLISECONDS.convert(timeout, this);
115	int ns = excessNanos(timeout, ms);
116	obj.wait(ms, ns);
117	}
118
119	/**
120	* Perform a timed <tt>Thread.join</tt> using the current time unit.
121	* This is a convenience method that converts time arguments into the
122	* form required by the <tt>Thread.join</tt> method.
123	* @param thread the thread to wait for
124	* @param timeout the maximum time to wait
125	* @throws InterruptedException if interrupted while waiting.
126	* @see Thread#join(long, int)
127	*/
128	public void timedJoin(Thread thread, long timeout)
129	throws InterruptedException {
130	long ms = MILLISECONDS.convert(timeout, this);
131	int ns = excessNanos(timeout, ms);
132	thread.join(ms, ns);
133	}
134
135	/**
136	* Perform a <tt>Thread.sleep</tt> using the current time unit.
137	* This is a convenience method that converts time arguments into the
138	* form required by the <tt>Thread.sleep</tt> method.
139	* @param time the minimum time to sleep
140	* @throws InterruptedException if interrupted while sleeping.
141	* @see Thread#sleep
142	*/
143	public void sleep(long timeout) throws InterruptedException {
144	long ms = MILLISECONDS.convert(timeout, this);
145	int ns = excessNanos(timeout, ms);
146	Thread.sleep(ms, ns);
147	}
148
149	/* ordered indices for each time unit */
150	private static final int NS = 0;
151	private static final int US = 1;
152	private static final int MS = 2;
153	private static final int S = 3;
154
155	/* quick lookup table for conversion factors */
156	static final int[] multipliers = { 1, 1000, 10001000, 10001000*1000 };
157
158	/* the index of this unit */
159	int index;
160
161	/** private constructor */
162	TimeUnit(int index) { this.index = index; }
163
164	/**
165	* Utility method to compute the excess-nanosecond argument to
166	* wait, sleep, join.
167	* @fixme overflow?
168	*/
169	private int excessNanos(long time, long ms) {
170	if (index == NS)
171	return (int) (time - (ms * multipliers[MS-NS]));
172	else if (index == US)
173	return (int) ((time * multipliers[US-NS]) - (ms * multipliers[MS-NS]));
174	else
175	return 0;
176	}
177
178	/** Underlying native time call */
179	static native long systemTimeNanos();
180
181	/** Unit for one-second granularities */
182	public static final TimeUnit SECONDS = new TimeUnit(S);
183
184	/** Unit for one-millisecond granularities */
185	public static final TimeUnit MILLISECONDS = new TimeUnit(MS);
186
187	/** Unit for one-microsecond granularities */
188	public static final TimeUnit MICROSECONDS = new TimeUnit(US);
189
190	/** Unit for one-nanosecond granularities */
191	public static final TimeUnit NANOSECONDS = new TimeUnit(NS);
192
193	}