package cron import ( "time" ) // SpecSchedule specifies a duty cycle (to the second granularity), based on a // traditional crontab specification. It is computed initially and stored as bit sets. type SpecSchedule struct { Second, Minute, Hour, Dom, Month, Dow uint64 } // bounds provides a range of acceptable values (plus a map of name to value). type bounds struct { min, max uint names map[string]uint } // The bounds for each field. var ( seconds = bounds{0, 59, nil} minutes = bounds{0, 59, nil} hours = bounds{0, 23, nil} dom = bounds{1, 31, nil} months = bounds{1, 12, map[string]uint{ "jan": 1, "feb": 2, "mar": 3, "apr": 4, "may": 5, "jun": 6, "jul": 7, "aug": 8, "sep": 9, "oct": 10, "nov": 11, "dec": 12, }} dow = bounds{0, 6, map[string]uint{ "sun": 0, "mon": 1, "tue": 2, "wed": 3, "thu": 4, "fri": 5, "sat": 6, }} ) const ( // Set the top bit if a star was included in the expression. starBit = 1 << 63 ) // Next returns the next time this schedule is activated, greater than the given // time. If no time can be found to satisfy the schedule, return the zero time. func (s *SpecSchedule) Next(t time.Time) time.Time { // General approach: // For Month, Day, Hour, Minute, Second: // Check if the time value matches. If yes, continue to the next field. // If the field doesn't match the schedule, then increment the field until it matches. // While incrementing the field, a wrap-around brings it back to the beginning // of the field list (since it is necessary to re-verify previous field // values) // Start at the earliest possible time (the upcoming second). t = t.Add(1*time.Second - time.Duration(t.Nanosecond())*time.Nanosecond) // This flag indicates whether a field has been incremented. added := false // If no time is found within five years, return zero. yearLimit := t.Year() + 5 WRAP: if t.Year() > yearLimit { return time.Time{} } // Find the first applicable month. // If it's this month, then do nothing. for 1<<uint(t.Month())&s.Month == 0 { // If we have to add a month, reset the other parts to 0. if !added { added = true // Otherwise, set the date at the beginning (since the current time is irrelevant). t = time.Date(t.Year(), t.Month(), 1, 0, 0, 0, 0, t.Location()) } t = t.AddDate(0, 1, 0) // Wrapped around. if t.Month() == time.January { goto WRAP } } // Now get a day in that month. for !dayMatches(s, t) { if !added { added = true t = time.Date(t.Year(), t.Month(), t.Day(), 0, 0, 0, 0, t.Location()) } t = t.AddDate(0, 0, 1) if t.Day() == 1 { goto WRAP } } for 1<<uint(t.Hour())&s.Hour == 0 { if !added { added = true t = time.Date(t.Year(), t.Month(), t.Day(), t.Hour(), 0, 0, 0, t.Location()) } t = t.Add(1 * time.Hour) if t.Hour() == 0 { goto WRAP } } for 1<<uint(t.Minute())&s.Minute == 0 { if !added { added = true t = time.Date(t.Year(), t.Month(), t.Day(), t.Hour(), t.Minute(), 0, 0, t.Location()) } t = t.Add(1 * time.Minute) if t.Minute() == 0 { goto WRAP } } for 1<<uint(t.Second())&s.Second == 0 { if !added { added = true t = time.Date(t.Year(), t.Month(), t.Day(), t.Hour(), t.Minute(), t.Second(), 0, t.Location()) } t = t.Add(1 * time.Second) if t.Second() == 0 { goto WRAP } } return t } // dayMatches returns true if the schedule's day-of-week and day-of-month // restrictions are satisfied by the given time. func dayMatches(s *SpecSchedule, t time.Time) bool { var ( domMatch bool = 1<<uint(t.Day())&s.Dom > 0 dowMatch bool = 1<<uint(t.Weekday())&s.Dow > 0 ) if s.Dom&starBit > 0 || s.Dow&starBit > 0 { return domMatch && dowMatch } return domMatch || dowMatch }