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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 = t.Truncate(time.Minute)
}
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 = t.Truncate(time.Second)
}
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
}