示例#1
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 /**
  * Obtains a clock that returns instants from the specified clock truncated
  * to the nearest occurrence of the specified duration.
  * <p>
  * This clock will only tick as per the specified duration. Thus, if the duration
  * is half a second, the clock will return instants truncated to the half second.
  * <p>
  * The tick duration must be positive. If it has a part smaller than a whole
  * millisecond, then the whole duration must divide into one second without
  * leaving a remainder. All normal tick durations will match these criteria,
  * including any multiple of hours, minutes, seconds and milliseconds, and
  * sensible nanosecond durations, such as 20ns, 250,000ns and 500,000ns.
  * <p>
  * A duration of zero or one nanosecond would have no truncation effect.
  * Passing one of these will return the underlying clock.
  * <p>
  * Implementations may use a caching strategy for performance reasons.
  * As such, it is possible that the start of the requested duration observed
  * via this clock will be later than that observed directly via the underlying clock.
  * <p>
  * The returned implementation is immutable, thread-safe and {@code Serializable}
  * providing that the base clock is.
  *
  * @param Clock $baseClock the base clock to base the ticking clock on, not null
  * @param Duration $tickDuration the duration of each visible tick, not negative, not null
  * @return Clock clock that ticks in whole units of the duration, not null
  * @throws \InvalidArgumentException if the duration is negative, or has a
  *  part smaller than a whole millisecond such that the whole duration is not
  *  divisible into one second
  * @throws ArithmeticException if the duration is too large to be represented as nanos
  */
 public static function tick(Clock $baseClock, Duration $tickDuration)
 {
     if ($tickDuration->isNegative()) {
         throw new \InvalidArgumentException("Tick duration must not be negative");
     }
     $tickNanos = $tickDuration->toNanos();
     if ($tickNanos % 1000000 == 0) {
         // ok, no fraction of millisecond
     } else {
         if (1000000000 % $tickNanos == 0) {
             // ok, divides into one second without remainder
         } else {
             throw new \InvalidArgumentException("Invalid tick duration");
         }
     }
     if ($tickNanos <= 1) {
         return $baseClock;
     }
     return new TickClock($baseClock, $tickNanos);
 }