Search the first timer to fire. * This operation is useful to know how many time the select can be * put in sleep without to delay any event. * If there are no timers NULL is returned. * * Note that's O(N) since time events are unsorted. * Possible optimizations (not needed by Disque so far, but...): * 1) Insert the event in order, so that the nearest is just the head. * Much better but
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