package cron import ( "fmt" "math" "strconv" "strings" "time" ) // ParseStandard returns a new crontab schedule representing the given standardSpec // (https://en.wikipedia.org/wiki/Cron). It differs from Parse requiring to always // pass 5 entries representing: minute, hour, day of month, month and day of week, // in that order. It returns a descriptive error if the spec is not valid. // // It accepts // - Standard crontab specs, e.g. "* * * * ?" // - Descriptors, e.g. "@midnight", "@every 1h30m" func ParseStandard(standardSpec string) (Schedule, error) { if standardSpec[0] == '@' { return parseDescriptor(standardSpec) } // Split on whitespace. We require exactly 5 fields. // (minute) (hour) (day of month) (month) (day of week) fields := strings.Fields(standardSpec) if len(fields) != 5 { return nil, fmt.Errorf("Expected exactly 5 fields, found %d: %s", len(fields), standardSpec) } var err error field := func(field string, r bounds) uint64 { if err != nil { return uint64(0) } var bits uint64 bits, err = getField(field, r) return bits } var ( minute = field(fields[0], minutes) hour = field(fields[1], hours) dayofmonth = field(fields[2], dom) month = field(fields[3], months) dayofweek = field(fields[4], dow) ) if err != nil { return nil, err } return &SpecSchedule{ Second: 1 << seconds.min, Minute: minute, Hour: hour, Dom: dayofmonth, Month: month, Dow: dayofweek, }, nil } // Parse returns a new crontab schedule representing the given spec. // It returns a descriptive error if the spec is not valid. // // It accepts // - Full crontab specs, e.g. "* * * * * ?" // - Descriptors, e.g. "@midnight", "@every 1h30m" func Parse(spec string) (Schedule, error) { if spec[0] == '@' { return parseDescriptor(spec) } // Split on whitespace. We require 5 or 6 fields. // (second) (minute) (hour) (day of month) (month) (day of week, optional) fields := strings.Fields(spec) if len(fields) != 5 && len(fields) != 6 { return nil, fmt.Errorf("Expected 5 or 6 fields, found %d: %s", len(fields), spec) } // If a sixth field is not provided (DayOfWeek), then it is equivalent to star. if len(fields) == 5 { fields = append(fields, "*") } var err error field := func(field string, r bounds) uint64 { if err != nil { return uint64(0) } var bits uint64 bits, err = getField(field, r) return bits } var ( second = field(fields[0], seconds) minute = field(fields[1], minutes) hour = field(fields[2], hours) dayofmonth = field(fields[3], dom) month = field(fields[4], months) dayofweek = field(fields[5], dow) ) if err != nil { return nil, err } return &SpecSchedule{ Second: second, Minute: minute, Hour: hour, Dom: dayofmonth, Month: month, Dow: dayofweek, }, nil } // getField returns an Int with the bits set representing all of the times that // the field represents or error parsing field value. A "field" is a comma-separated // list of "ranges". func getField(field string, r bounds) (uint64, error) { var bits uint64 ranges := strings.FieldsFunc(field, func(r rune) bool { return r == ',' }) for _, expr := range ranges { bit, err := getRange(expr, r) if err != nil { return bits, err } bits |= bit } return bits, nil } // getRange returns the bits indicated by the given expression: // number | number "-" number [ "/" number ] // or error parsing range. func getRange(expr string, r bounds) (uint64, error) { var ( start, end, step uint rangeAndStep = strings.Split(expr, "/") lowAndHigh = strings.Split(rangeAndStep[0], "-") singleDigit = len(lowAndHigh) == 1 err error zero = uint64(0) ) var extra_star uint64 if lowAndHigh[0] == "*" || lowAndHigh[0] == "?" { start = r.min end = r.max extra_star = starBit } else { start, err = parseIntOrName(lowAndHigh[0], r.names) if err != nil { return zero, err } switch len(lowAndHigh) { case 1: end = start case 2: end, err = parseIntOrName(lowAndHigh[1], r.names) if err != nil { return zero, err } default: return zero, fmt.Errorf("Too many hyphens: %s", expr) } } switch len(rangeAndStep) { case 1: step = 1 case 2: step, err = mustParseInt(rangeAndStep[1]) if err != nil { return zero, err } // Special handling: "N/step" means "N-max/step". if singleDigit { end = r.max } default: return zero, fmt.Errorf("Too many slashes: %s", expr) } if start < r.min { return zero, fmt.Errorf("Beginning of range (%d) below minimum (%d): %s", start, r.min, expr) } if end > r.max { return zero, fmt.Errorf("End of range (%d) above maximum (%d): %s", end, r.max, expr) } if start > end { return zero, fmt.Errorf("Beginning of range (%d) beyond end of range (%d): %s", start, end, expr) } if step == 0 { return zero, fmt.Errorf("Step of range should be a positive number: %s", expr) } return getBits(start, end, step) | extra_star, nil } // parseIntOrName returns the (possibly-named) integer contained in expr. func parseIntOrName(expr string, names map[string]uint) (uint, error) { if names != nil { if namedInt, ok := names[strings.ToLower(expr)]; ok { return namedInt, nil } } return mustParseInt(expr) } // mustParseInt parses the given expression as an int or returns an error. func mustParseInt(expr string) (uint, error) { num, err := strconv.Atoi(expr) if err != nil { return 0, fmt.Errorf("Failed to parse int from %s: %s", expr, err) } if num < 0 { return 0, fmt.Errorf("Negative number (%d) not allowed: %s", num, expr) } return uint(num), nil } // getBits sets all bits in the range [min, max], modulo the given step size. func getBits(min, max, step uint) uint64 { var bits uint64 // If step is 1, use shifts. if step == 1 { return ^(math.MaxUint64 << (max + 1)) & (math.MaxUint64 << min) } // Else, use a simple loop. for i := min; i <= max; i += step { bits |= 1 << i } return bits } // all returns all bits within the given bounds. (plus the star bit) func all(r bounds) uint64 { return getBits(r.min, r.max, 1) | starBit } // parseDescriptor returns a predefined schedule for the expression, or error if none matches. func parseDescriptor(descriptor string) (Schedule, error) { switch descriptor { case "@yearly", "@annually": return &SpecSchedule{ Second: 1 << seconds.min, Minute: 1 << minutes.min, Hour: 1 << hours.min, Dom: 1 << dom.min, Month: 1 << months.min, Dow: all(dow), }, nil case "@monthly": return &SpecSchedule{ Second: 1 << seconds.min, Minute: 1 << minutes.min, Hour: 1 << hours.min, Dom: 1 << dom.min, Month: all(months), Dow: all(dow), }, nil case "@weekly": return &SpecSchedule{ Second: 1 << seconds.min, Minute: 1 << minutes.min, Hour: 1 << hours.min, Dom: all(dom), Month: all(months), Dow: 1 << dow.min, }, nil case "@daily", "@midnight": return &SpecSchedule{ Second: 1 << seconds.min, Minute: 1 << minutes.min, Hour: 1 << hours.min, Dom: all(dom), Month: all(months), Dow: all(dow), }, nil case "@hourly": return &SpecSchedule{ Second: 1 << seconds.min, Minute: 1 << minutes.min, Hour: all(hours), Dom: all(dom), Month: all(months), Dow: all(dow), }, nil } const every = "@every " if strings.HasPrefix(descriptor, every) { duration, err := time.ParseDuration(descriptor[len(every):]) if err != nil { return nil, fmt.Errorf("Failed to parse duration %s: %s", descriptor, err) } return Every(duration), nil } return nil, fmt.Errorf("Unrecognized descriptor: %s", descriptor) }