Adding github.com/robfig/cron for cron parsing

Godeps/Godeps.json

@@ -1761,6 +1761,10 @@
 			"Rev": "8992d7483a06748dea706e4716d042a4a9e73918"
 		},
 		{
+			"ImportPath": "github.com/robfig/cron",
+			"Rev": "0f39cf7ebc65a602f45692f9894bd6a193faf8fa"
+		},
+		{
 			"ImportPath": "github.com/russross/blackfriday",
 			"Comment": "v1.2-42-g77efab5",
 			"Rev": "77efab57b2f74dd3f9051c79752b2e8995c8b789"

Godeps/LICENSES

@@ -59126,6 +59126,32 @@ specific language governing permissions and limitations under the License.
 
 
 ================================================================================
+= vendor/github.com/robfig/cron licensed under: =
+
+Copyright (C) 2012 Rob Figueiredo
+All Rights Reserved.
+
+MIT LICENSE
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+
+================================================================================
 = vendor/github.com/russross/blackfriday licensed under: =
 
 Blackfriday is distributed under the Simplified BSD License:

vendor/github.com/robfig/cron/.gitignore

+# Compiled Object files, Static and Dynamic libs (Shared Objects)
+*.o
+*.a
+*.so
+
+# Folders
+_obj
+_test
+
+# Architecture specific extensions/prefixes
+*.[568vq]
+[568vq].out
+
+*.cgo1.go
+*.cgo2.c
+_cgo_defun.c
+_cgo_gotypes.go
+_cgo_export.*
+
+_testmain.go
+
+*.exe

vendor/github.com/robfig/cron/.travis.yml

+language: go

vendor/github.com/robfig/cron/LICENSE

+Copyright (C) 2012 Rob Figueiredo
+All Rights Reserved.
+
+MIT LICENSE
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

vendor/github.com/robfig/cron/README.md

+[![GoDoc](http://godoc.org/github.com/robfig/cron?status.png)](http://godoc.org/github.com/robfig/cron)
+[![Build Status](https://travis-ci.org/robfig/cron.svg?branch=master)](https://travis-ci.org/robfig/cron)

vendor/github.com/robfig/cron/constantdelay.go

+package cron
+
+import "time"
+
+// ConstantDelaySchedule represents a simple recurring duty cycle, e.g. "Every 5 minutes".
+// It does not support jobs more frequent than once a second.
+type ConstantDelaySchedule struct {
+	Delay time.Duration
+}
+
+// Every returns a crontab Schedule that activates once every duration.
+// Delays of less than a second are not supported (will round up to 1 second).
+// Any fields less than a Second are truncated.
+func Every(duration time.Duration) ConstantDelaySchedule {
+	if duration < time.Second {
+		duration = time.Second
+	}
+	return ConstantDelaySchedule{
+		Delay: duration - time.Duration(duration.Nanoseconds())%time.Second,
+	}
+}
+
+// Next returns the next time this should be run.
+// This rounds so that the next activation time will be on the second.
+func (schedule ConstantDelaySchedule) Next(t time.Time) time.Time {
+	return t.Add(schedule.Delay - time.Duration(t.Nanosecond())*time.Nanosecond)
+}

vendor/github.com/robfig/cron/cron.go

+// This library implements a cron spec parser and runner.  See the README for
+// more details.
+package cron
+
+import (
+	"log"
+	"runtime"
+	"sort"
+	"time"
+)
+
+// Cron keeps track of any number of entries, invoking the associated func as
+// specified by the schedule. It may be started, stopped, and the entries may
+// be inspected while running.
+type Cron struct {
+	entries  []*Entry
+	stop     chan struct{}
+	add      chan *Entry
+	snapshot chan []*Entry
+	running  bool
+	ErrorLog *log.Logger
+}
+
+// Job is an interface for submitted cron jobs.
+type Job interface {
+	Run()
+}
+
+// The Schedule describes a job's duty cycle.
+type Schedule interface {
+	// Return the next activation time, later than the given time.
+	// Next is invoked initially, and then each time the job is run.
+	Next(time.Time) time.Time
+}
+
+// Entry consists of a schedule and the func to execute on that schedule.
+type Entry struct {
+	// The schedule on which this job should be run.
+	Schedule Schedule
+
+	// The next time the job will run. This is the zero time if Cron has not been
+	// started or this entry's schedule is unsatisfiable
+	Next time.Time
+
+	// The last time this job was run. This is the zero time if the job has never
+	// been run.
+	Prev time.Time
+
+	// The Job to run.
+	Job Job
+}
+
+// byTime is a wrapper for sorting the entry array by time
+// (with zero time at the end).
+type byTime []*Entry
+
+func (s byTime) Len() int      { return len(s) }
+func (s byTime) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
+func (s byTime) Less(i, j int) bool {
+	// Two zero times should return false.
+	// Otherwise, zero is "greater" than any other time.
+	// (To sort it at the end of the list.)
+	if s[i].Next.IsZero() {
+		return false
+	}
+	if s[j].Next.IsZero() {
+		return true
+	}
+	return s[i].Next.Before(s[j].Next)
+}
+
+// New returns a new Cron job runner.
+func New() *Cron {
+	return &Cron{
+		entries:  nil,
+		add:      make(chan *Entry),
+		stop:     make(chan struct{}),
+		snapshot: make(chan []*Entry),
+		running:  false,
+		ErrorLog: nil,
+	}
+}
+
+// A wrapper that turns a func() into a cron.Job
+type FuncJob func()
+
+func (f FuncJob) Run() { f() }
+
+// AddFunc adds a func to the Cron to be run on the given schedule.
+func (c *Cron) AddFunc(spec string, cmd func()) error {
+	return c.AddJob(spec, FuncJob(cmd))
+}
+
+// AddJob adds a Job to the Cron to be run on the given schedule.
+func (c *Cron) AddJob(spec string, cmd Job) error {
+	schedule, err := Parse(spec)
+	if err != nil {
+		return err
+	}
+	c.Schedule(schedule, cmd)
+	return nil
+}
+
+// Schedule adds a Job to the Cron to be run on the given schedule.
+func (c *Cron) Schedule(schedule Schedule, cmd Job) {
+	entry := &Entry{
+		Schedule: schedule,
+		Job:      cmd,
+	}
+	if !c.running {
+		c.entries = append(c.entries, entry)
+		return
+	}
+
+	c.add <- entry
+}
+
+// Entries returns a snapshot of the cron entries.
+func (c *Cron) Entries() []*Entry {
+	if c.running {
+		c.snapshot <- nil
+		x := <-c.snapshot
+		return x
+	}
+	return c.entrySnapshot()
+}
+
+// Start the cron scheduler in its own go-routine.
+func (c *Cron) Start() {
+	c.running = true
+	go c.run()
+}
+
+func (c *Cron) runWithRecovery(j Job) {
+	defer func() {
+		if r := recover(); r != nil {
+			const size = 64 << 10
+			buf := make([]byte, size)
+			buf = buf[:runtime.Stack(buf, false)]
+			c.logf("cron: panic running job: %v\n%s", r, buf)
+		}
+	}()
+	j.Run()
+}
+
+// Run the scheduler.. this is private just due to the need to synchronize
+// access to the 'running' state variable.
+func (c *Cron) run() {
+	// Figure out the next activation times for each entry.
+	now := time.Now().Local()
+	for _, entry := range c.entries {
+		entry.Next = entry.Schedule.Next(now)
+	}
+
+	for {
+		// Determine the next entry to run.
+		sort.Sort(byTime(c.entries))
+
+		var effective time.Time
+		if len(c.entries) == 0 || c.entries[0].Next.IsZero() {
+			// If there are no entries yet, just sleep - it still handles new entries
+			// and stop requests.
+			effective = now.AddDate(10, 0, 0)
+		} else {
+			effective = c.entries[0].Next
+		}
+
+		select {
+		case now = <-time.After(effective.Sub(now)):
+			// Run every entry whose next time was this effective time.
+			for _, e := range c.entries {
+				if e.Next != effective {
+					break
+				}
+				go c.runWithRecovery(e.Job)
+				e.Prev = e.Next
+				e.Next = e.Schedule.Next(effective)
+			}
+			continue
+
+		case newEntry := <-c.add:
+			c.entries = append(c.entries, newEntry)
+			newEntry.Next = newEntry.Schedule.Next(time.Now().Local())
+
+		case <-c.snapshot:
+			c.snapshot <- c.entrySnapshot()
+
+		case <-c.stop:
+			return
+		}
+
+		// 'now' should be updated after newEntry and snapshot cases.
+		now = time.Now().Local()
+	}
+}
+
+// Logs an error to stderr or to the configured error log
+func (c *Cron) logf(format string, args ...interface{}) {
+	if c.ErrorLog != nil {
+		c.ErrorLog.Printf(format, args...)
+	} else {
+		log.Printf(format, args...)
+	}
+}
+
+// Stop stops the cron scheduler if it is running; otherwise it does nothing.
+func (c *Cron) Stop() {
+	if !c.running {
+		return
+	}
+	c.stop <- struct{}{}
+	c.running = false
+}
+
+// entrySnapshot returns a copy of the current cron entry list.
+func (c *Cron) entrySnapshot() []*Entry {
+	entries := []*Entry{}
+	for _, e := range c.entries {
+		entries = append(entries, &Entry{
+			Schedule: e.Schedule,
+			Next:     e.Next,
+			Prev:     e.Prev,
+			Job:      e.Job,
+		})
+	}
+	return entries
+}

vendor/github.com/robfig/cron/doc.go

+/*
+Package cron implements a cron spec parser and job runner.
+
+Usage
+
+Callers may register Funcs to be invoked on a given schedule.  Cron will run
+them in their own goroutines.
+
+	c := cron.New()
+	c.AddFunc("0 30 * * * *", func() { fmt.Println("Every hour on the half hour") })
+	c.AddFunc("@hourly",      func() { fmt.Println("Every hour") })
+	c.AddFunc("@every 1h30m", func() { fmt.Println("Every hour thirty") })
+	c.Start()
+	..
+	// Funcs are invoked in their own goroutine, asynchronously.
+	...
+	// Funcs may also be added to a running Cron
+	c.AddFunc("@daily", func() { fmt.Println("Every day") })
+	..
+	// Inspect the cron job entries' next and previous run times.
+	inspect(c.Entries())
+	..
+	c.Stop()  // Stop the scheduler (does not stop any jobs already running).
+
+CRON Expression Format
+
+A cron expression represents a set of times, using 6 space-separated fields.
+
+	Field name   | Mandatory? | Allowed values  | Allowed special characters
+	----------   | ---------- | --------------  | --------------------------
+	Seconds      | Yes        | 0-59            | * / , -
+	Minutes      | Yes        | 0-59            | * / , -
+	Hours        | Yes        | 0-23            | * / , -
+	Day of month | Yes        | 1-31            | * / , - ?
+	Month        | Yes        | 1-12 or JAN-DEC | * / , -
+	Day of week  | Yes        | 0-6 or SUN-SAT  | * / , - ?
+
+Note: Month and Day-of-week field values are case insensitive.  "SUN", "Sun",
+and "sun" are equally accepted.
+
+Special Characters
+
+Asterisk ( * )
+
+The asterisk indicates that the cron expression will match for all values of the
+field; e.g., using an asterisk in the 5th field (month) would indicate every
+month.
+
+Slash ( / )
+
+Slashes are used to describe increments of ranges. For example 3-59/15 in the
+1st field (minutes) would indicate the 3rd minute of the hour and every 15
+minutes thereafter. The form "*\/..." is equivalent to the form "first-last/...",
+that is, an increment over the largest possible range of the field.  The form
+"N/..." is accepted as meaning "N-MAX/...", that is, starting at N, use the
+increment until the end of that specific range.  It does not wrap around.
+
+Comma ( , )
+
+Commas are used to separate items of a list. For example, using "MON,WED,FRI" in
+the 5th field (day of week) would mean Mondays, Wednesdays and Fridays.
+
+Hyphen ( - )
+
+Hyphens are used to define ranges. For example, 9-17 would indicate every
+hour between 9am and 5pm inclusive.
+
+Question mark ( ? )
+
+Question mark may be used instead of '*' for leaving either day-of-month or
+day-of-week blank.
+
+Predefined schedules
+
+You may use one of several pre-defined schedules in place of a cron expression.
+
+	Entry                  | Description                                | Equivalent To
+	-----                  | -----------                                | -------------
+	@yearly (or @annually) | Run once a year, midnight, Jan. 1st        | 0 0 0 1 1 *
+	@monthly               | Run once a month, midnight, first of month | 0 0 0 1 * *
+	@weekly                | Run once a week, midnight on Sunday        | 0 0 0 * * 0
+	@daily (or @midnight)  | Run once a day, midnight                   | 0 0 0 * * *
+	@hourly                | Run once an hour, beginning of hour        | 0 0 * * * *
+
+Intervals
+
+You may also schedule a job to execute at fixed intervals.  This is supported by
+formatting the cron spec like this:
+
+    @every <duration>
+
+where "duration" is a string accepted by time.ParseDuration
+(http://golang.org/pkg/time/#ParseDuration).
+
+For example, "@every 1h30m10s" would indicate a schedule that activates every
+1 hour, 30 minutes, 10 seconds.
+
+Note: The interval does not take the job runtime into account.  For example,
+if a job takes 3 minutes to run, and it is scheduled to run every 5 minutes,
+it will have only 2 minutes of idle time between each run.
+
+Time zones
+
+All interpretation and scheduling is done in the machine's local time zone (as
+provided by the Go time package (http://www.golang.org/pkg/time).
+
+Be aware that jobs scheduled during daylight-savings leap-ahead transitions will
+not be run!
+
+Thread safety
+
+Since the Cron service runs concurrently with the calling code, some amount of
+care must be taken to ensure proper synchronization.
+
+All cron methods are designed to be correctly synchronized as long as the caller
+ensures that invocations have a clear happens-before ordering between them.
+
+Implementation
+
+Cron entries are stored in an array, sorted by their next activation time.  Cron
+sleeps until the next job is due to be run.
+
+Upon waking:
+ - it runs each entry that is active on that second
+ - it calculates the next run times for the jobs that were run
+ - it re-sorts the array of entries by next activation time.
+ - it goes to sleep until the soonest job.
+*/
+package cron

vendor/github.com/robfig/cron/parser.go

+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
+}

vendor/github.com/robfig/cron/spec.go

+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 = t.Truncate(time.Hour)
+		}
+		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
+}