/*
* @(#)TimeUnit.java 1.6 04/02/09
*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
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. A
* <tt>TimeUnit</tt> does not maintain time information, but only
* helps organize and use time representations that may be maintained
* separately across various contexts.
*
* <p>A <tt>TimeUnit</tt> is mainly used to inform time-based methods
* how a given timing 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 enum TimeUnit {
NANOSECONDS(0), MICROSECONDS(1), MILLISECONDS(2), SECONDS(3);
/** the index of this unit */
private final int index;
/** Internal constructor */
TimeUnit(int index) {
this.index = index;
}
/** Lookup table for conversion factors */
private static final int[] multipliers = {
1,
1000,
1000 * 1000,
1000 * 1000 * 1000
};
/**
* Lookup table to check saturation. Note that because we are
* dividing these down, we don't have to deal with asymmetry of
* MIN/MAX values.
*/
private static final long[] overflows = {
0, // unused
Long.MAX_VALUE / 1000,
Long.MAX_VALUE / (1000 * 1000),
Long.MAX_VALUE / (1000 * 1000 * 1000)
};
/**
* 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 - MICROSECONDS.index, 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 - MILLISECONDS.index, 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 - SECONDS.index, duration);
}
/**
* Utility method to compute the excess-nanosecond argument to
* wait, sleep, join.
*/
private int excessNanos(long time, long ms) {
if (this == NANOSECONDS)
return (int) (time - (ms * 1000 * 1000));
if (this == MICROSECONDS)
return (int) ((time * 1000) - (ms * 1000 * 1000));
return 0;
}
/**
* 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);
}
}
}
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