mirror of
https://github.com/crazy-max/diun.git
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436 lines
11 KiB
Go
436 lines
11 KiB
Go
package cron
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import (
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"fmt"
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"math"
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"strconv"
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"strings"
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"time"
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)
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// ParseOption options for creating a parser. Most options specify which
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// fields should be included, while others enable features. If a field is not
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// included the parser will assume a default value. These options do not change
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// the order fields are parse in.
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type ParseOption int
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const (
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Second ParseOption = 1 << iota // Seconds field, default 0
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SecondOptional // Optional seconds field, default 0
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Minute // Minutes field, default 0
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Hour // Hours field, default 0
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Dom // Day of month field, default *
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Month // Month field, default *
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Dow // Day of week field, default *
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DowOptional // Optional day of week field, default *
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Descriptor // Allow descriptors such as @monthly, @weekly, etc.
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)
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var places = []ParseOption{
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Second,
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Minute,
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Hour,
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Dom,
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Month,
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Dow,
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}
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var defaults = []string{
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"0",
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"0",
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"0",
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"*",
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"*",
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"*",
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}
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// Parser is a custom parser that can be configured.
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type Parser struct {
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options ParseOption
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}
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// NewParser creates a Parser with custom options.
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//
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// It panics if more than one Optional is given, since it would be impossible to
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// correctly infer which optional is provided or missing in general.
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//
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// Examples
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//
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// // Standard parser without descriptors
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// specParser := NewParser(Minute | Hour | Dom | Month | Dow)
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// sched, err := specParser.Parse("0 0 15 */3 *")
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//
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// // Same as above, just excludes time fields
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// specParser := NewParser(Dom | Month | Dow)
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// sched, err := specParser.Parse("15 */3 *")
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//
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// // Same as above, just makes Dow optional
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// specParser := NewParser(Dom | Month | DowOptional)
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// sched, err := specParser.Parse("15 */3")
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func NewParser(options ParseOption) Parser {
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optionals := 0
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if options&DowOptional > 0 {
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optionals++
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}
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if options&SecondOptional > 0 {
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optionals++
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}
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if optionals > 1 {
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panic("multiple optionals may not be configured")
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}
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return Parser{options}
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}
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// Parse returns a new crontab schedule representing the given spec.
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// It returns a descriptive error if the spec is not valid.
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// It accepts crontab specs and features configured by NewParser.
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func (p Parser) Parse(spec string) (Schedule, error) {
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if len(spec) == 0 {
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return nil, fmt.Errorf("empty spec string")
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}
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// Extract timezone if present
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var loc = time.Local
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if strings.HasPrefix(spec, "TZ=") || strings.HasPrefix(spec, "CRON_TZ=") {
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var err error
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i := strings.Index(spec, " ")
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eq := strings.Index(spec, "=")
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if loc, err = time.LoadLocation(spec[eq+1 : i]); err != nil {
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return nil, fmt.Errorf("provided bad location %s: %v", spec[eq+1:i], err)
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}
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spec = strings.TrimSpace(spec[i:])
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}
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// Handle named schedules (descriptors), if configured
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if strings.HasPrefix(spec, "@") {
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if p.options&Descriptor == 0 {
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return nil, fmt.Errorf("parser does not accept descriptors: %v", spec)
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}
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return parseDescriptor(spec, loc)
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}
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// Split on whitespace.
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fields := strings.Fields(spec)
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// Validate & fill in any omitted or optional fields
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var err error
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fields, err = normalizeFields(fields, p.options)
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if err != nil {
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return nil, err
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}
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field := func(field string, r bounds) uint64 {
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if err != nil {
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return 0
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}
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var bits uint64
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bits, err = getField(field, r)
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return bits
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}
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var (
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second = field(fields[0], seconds)
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minute = field(fields[1], minutes)
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hour = field(fields[2], hours)
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dayofmonth = field(fields[3], dom)
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month = field(fields[4], months)
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dayofweek = field(fields[5], dow)
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)
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if err != nil {
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return nil, err
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}
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return &SpecSchedule{
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Second: second,
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Minute: minute,
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Hour: hour,
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Dom: dayofmonth,
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Month: month,
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Dow: dayofweek,
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Location: loc,
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}, nil
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}
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// normalizeFields takes a subset set of the time fields and returns the full set
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// with defaults (zeroes) populated for unset fields.
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//
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// As part of performing this function, it also validates that the provided
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// fields are compatible with the configured options.
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func normalizeFields(fields []string, options ParseOption) ([]string, error) {
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// Validate optionals & add their field to options
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optionals := 0
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if options&SecondOptional > 0 {
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options |= Second
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optionals++
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}
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if options&DowOptional > 0 {
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options |= Dow
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optionals++
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}
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if optionals > 1 {
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return nil, fmt.Errorf("multiple optionals may not be configured")
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}
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// Figure out how many fields we need
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max := 0
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for _, place := range places {
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if options&place > 0 {
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max++
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}
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}
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min := max - optionals
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// Validate number of fields
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if count := len(fields); count < min || count > max {
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if min == max {
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return nil, fmt.Errorf("expected exactly %d fields, found %d: %s", min, count, fields)
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}
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return nil, fmt.Errorf("expected %d to %d fields, found %d: %s", min, max, count, fields)
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}
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// Populate the optional field if not provided
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if min < max && len(fields) == min {
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switch {
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case options&DowOptional > 0:
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fields = append(fields, defaults[5]) // TODO: improve access to default
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case options&SecondOptional > 0:
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fields = append([]string{defaults[0]}, fields...)
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default:
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return nil, fmt.Errorf("unknown optional field")
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}
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}
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// Populate all fields not part of options with their defaults
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n := 0
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expandedFields := make([]string, len(places))
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copy(expandedFields, defaults)
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for i, place := range places {
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if options&place > 0 {
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expandedFields[i] = fields[n]
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n++
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}
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}
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return expandedFields, nil
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}
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var standardParser = NewParser(
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Minute | Hour | Dom | Month | Dow | Descriptor,
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)
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// ParseStandard returns a new crontab schedule representing the given
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// standardSpec (https://en.wikipedia.org/wiki/Cron). It requires 5 entries
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// representing: minute, hour, day of month, month and day of week, in that
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// order. It returns a descriptive error if the spec is not valid.
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//
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// It accepts
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// - Standard crontab specs, e.g. "* * * * ?"
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// - Descriptors, e.g. "@midnight", "@every 1h30m"
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func ParseStandard(standardSpec string) (Schedule, error) {
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return standardParser.Parse(standardSpec)
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}
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// getField returns an Int with the bits set representing all of the times that
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// the field represents or error parsing field value. A "field" is a comma-separated
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// list of "ranges".
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func getField(field string, r bounds) (uint64, error) {
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var bits uint64
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ranges := strings.FieldsFunc(field, func(r rune) bool { return r == ',' })
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for _, expr := range ranges {
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bit, err := getRange(expr, r)
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if err != nil {
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return bits, err
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}
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bits |= bit
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}
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return bits, nil
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}
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// getRange returns the bits indicated by the given expression:
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//
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// number | number "-" number [ "/" number ]
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//
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// or error parsing range.
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func getRange(expr string, r bounds) (uint64, error) {
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var (
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start, end, step uint
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rangeAndStep = strings.Split(expr, "/")
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lowAndHigh = strings.Split(rangeAndStep[0], "-")
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singleDigit = len(lowAndHigh) == 1
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err error
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)
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var extra uint64
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if lowAndHigh[0] == "*" || lowAndHigh[0] == "?" {
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start = r.min
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end = r.max
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extra = starBit
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} else {
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start, err = parseIntOrName(lowAndHigh[0], r.names)
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if err != nil {
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return 0, err
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}
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switch len(lowAndHigh) {
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case 1:
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end = start
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case 2:
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end, err = parseIntOrName(lowAndHigh[1], r.names)
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if err != nil {
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return 0, err
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}
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default:
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return 0, fmt.Errorf("too many hyphens: %s", expr)
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}
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}
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switch len(rangeAndStep) {
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case 1:
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step = 1
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case 2:
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step, err = mustParseInt(rangeAndStep[1])
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if err != nil {
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return 0, err
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}
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// Special handling: "N/step" means "N-max/step".
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if singleDigit {
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end = r.max
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}
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if step > 1 {
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extra = 0
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}
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default:
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return 0, fmt.Errorf("too many slashes: %s", expr)
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}
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if start < r.min {
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return 0, fmt.Errorf("beginning of range (%d) below minimum (%d): %s", start, r.min, expr)
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}
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if end > r.max {
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return 0, fmt.Errorf("end of range (%d) above maximum (%d): %s", end, r.max, expr)
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}
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if start > end {
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return 0, fmt.Errorf("beginning of range (%d) beyond end of range (%d): %s", start, end, expr)
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}
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if step == 0 {
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return 0, fmt.Errorf("step of range should be a positive number: %s", expr)
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}
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return getBits(start, end, step) | extra, nil
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}
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// parseIntOrName returns the (possibly-named) integer contained in expr.
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func parseIntOrName(expr string, names map[string]uint) (uint, error) {
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if names != nil {
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if namedInt, ok := names[strings.ToLower(expr)]; ok {
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return namedInt, nil
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}
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}
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return mustParseInt(expr)
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}
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// mustParseInt parses the given expression as an int or returns an error.
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func mustParseInt(expr string) (uint, error) {
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num, err := strconv.Atoi(expr)
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if err != nil {
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return 0, fmt.Errorf("failed to parse int from %s: %s", expr, err)
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}
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if num < 0 {
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return 0, fmt.Errorf("negative number (%d) not allowed: %s", num, expr)
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}
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return uint(num), nil
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}
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// getBits sets all bits in the range [min, max], modulo the given step size.
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func getBits(min, max, step uint) uint64 {
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var bits uint64
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// If step is 1, use shifts.
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if step == 1 {
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return ^(math.MaxUint64 << (max + 1)) & (math.MaxUint64 << min)
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}
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// Else, use a simple loop.
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for i := min; i <= max; i += step {
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bits |= 1 << i
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}
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return bits
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}
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// all returns all bits within the given bounds. (plus the star bit)
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func all(r bounds) uint64 {
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return getBits(r.min, r.max, 1) | starBit
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}
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// parseDescriptor returns a predefined schedule for the expression, or error if none matches.
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func parseDescriptor(descriptor string, loc *time.Location) (Schedule, error) {
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switch descriptor {
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case "@yearly", "@annually":
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return &SpecSchedule{
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Second: 1 << seconds.min,
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Minute: 1 << minutes.min,
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Hour: 1 << hours.min,
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Dom: 1 << dom.min,
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Month: 1 << months.min,
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Dow: all(dow),
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Location: loc,
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}, nil
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case "@monthly":
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return &SpecSchedule{
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Second: 1 << seconds.min,
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Minute: 1 << minutes.min,
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Hour: 1 << hours.min,
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Dom: 1 << dom.min,
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Month: all(months),
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Dow: all(dow),
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Location: loc,
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}, nil
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case "@weekly":
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return &SpecSchedule{
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Second: 1 << seconds.min,
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Minute: 1 << minutes.min,
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Hour: 1 << hours.min,
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Dom: all(dom),
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Month: all(months),
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Dow: 1 << dow.min,
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Location: loc,
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}, nil
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case "@daily", "@midnight":
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return &SpecSchedule{
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Second: 1 << seconds.min,
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Minute: 1 << minutes.min,
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Hour: 1 << hours.min,
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Dom: all(dom),
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Month: all(months),
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Dow: all(dow),
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Location: loc,
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}, nil
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case "@hourly":
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return &SpecSchedule{
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Second: 1 << seconds.min,
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Minute: 1 << minutes.min,
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Hour: all(hours),
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Dom: all(dom),
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Month: all(months),
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Dow: all(dow),
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Location: loc,
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}, nil
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}
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const every = "@every "
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if strings.HasPrefix(descriptor, every) {
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duration, err := time.ParseDuration(descriptor[len(every):])
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if err != nil {
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return nil, fmt.Errorf("failed to parse duration %s: %s", descriptor, err)
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}
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return Every(duration), nil
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}
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return nil, fmt.Errorf("unrecognized descriptor: %s", descriptor)
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}
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