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package cron
import (
"fmt"
"log"
"math"
"strconv"
"strings"
"time"
)
// 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, err error) {
// Convert panics into errors
defer func() {
if recovered := recover(); recovered != nil {
err = fmt.Errorf("%v", recovered)
}
}()
if spec[0] == '@' {
return parseDescriptor(spec), nil
}
// 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 {
log.Panicf("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, "*")
}
schedule := &SpecSchedule{
Second: getField(fields[0], seconds),
Minute: getField(fields[1], minutes),
Hour: getField(fields[2], hours),
Dom: getField(fields[3], dom),
Month: getField(fields[4], months),
Dow: getField(fields[5], dow),
}
return schedule, nil
}
// getField returns an Int with the bits set representing all of the times that
// the field represents. A "field" is a comma-separated list of "ranges".
func getField(field string, r bounds) uint64 {
// list = range {"," range}
var bits uint64
ranges := strings.FieldsFunc(field, func(r rune) bool { return r == ',' })
for _, expr := range ranges {
bits |= getRange(expr, r)
}
return bits
}
// getRange returns the bits indicated by the given expression:
// number | number "-" number [ "/" number ]
func getRange(expr string, r bounds) uint64 {
var (
start, end, step uint
rangeAndStep = strings.Split(expr, "/")
lowAndHigh = strings.Split(rangeAndStep[0], "-")
singleDigit = len(lowAndHigh) == 1
)
var extra_star uint64
if lowAndHigh[0] == "*" || lowAndHigh[0] == "?" {
start = r.min
end = r.max
extra_star = starBit
} else {
start = parseIntOrName(lowAndHigh[0], r.names)
switch len(lowAndHigh) {
case 1:
end = start
case 2:
end = parseIntOrName(lowAndHigh[1], r.names)
default:
log.Panicf("Too many hyphens: %s", expr)
}
}
switch len(rangeAndStep) {
case 1:
step = 1
case 2:
step = mustParseInt(rangeAndStep[1])
// Special handling: "N/step" means "N-max/step".
if singleDigit {
end = r.max
}
default:
log.Panicf("Too many slashes: %s", expr)
}
if start < r.min {
log.Panicf("Beginning of range (%d) below minimum (%d): %s", start, r.min, expr)
}
if end > r.max {
log.Panicf("End of range (%d) above maximum (%d): %s", end, r.max, expr)
}
if start > end {
log.Panicf("Beginning of range (%d) beyond end of range (%d): %s", start, end, expr)
}
return getBits(start, end, step) | extra_star
}
// parseIntOrName returns the (possibly-named) integer contained in expr.
func parseIntOrName(expr string, names map[string]uint) uint {
if names != nil {
if namedInt, ok := names[strings.ToLower(expr)]; ok {
return namedInt
}
}
return mustParseInt(expr)
}
// mustParseInt parses the given expression as an int or panics.
func mustParseInt(expr string) uint {
num, err := strconv.Atoi(expr)
if err != nil {
log.Panicf("Failed to parse int from %s: %s", expr, err)
}
if num < 0 {
log.Panicf("Negative number (%d) not allowed: %s", num, expr)
}
return uint(num)
}
// 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 pre-defined schedule for the expression, or panics
// if none matches.
func parseDescriptor(spec string) Schedule {
switch spec {
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),
}
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),
}
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,
}
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),
}
case "@hourly":
return &SpecSchedule{
Second: 1 << seconds.min,
Minute: 1 << minutes.min,
Hour: all(hours),
Dom: all(dom),
Month: all(months),
Dow: all(dow),
}
}
const every = "@every "
if strings.HasPrefix(spec, every) {
duration, err := time.ParseDuration(spec[len(every):])
if err != nil {
log.Panicf("Failed to parse duration %s: %s", spec, err)
}
return Every(duration)
}
log.Panicf("Unrecognized descriptor: %s", spec)
return nil
}
|
