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cronexpr
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added package doc, as per issue 2

This commit is contained in:
gorhill 2013-08-30 11:40:02 -04:00
parent eefaec0758
commit d3a85f92d8
1 changed files with 24 additions and 26 deletions
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50
cronexpression.go
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@ -23,11 +23,10 @@ import (
/******************************************************************************/
// A CronExpression represents a specific cron expression as defined on
// A CronExpression represents a specific cron time expression as defined on
// Wikipedia: https://en.wikipedia.org/wiki/Cron#CRON_expression
//
type CronExpression struct {
Expression string
expression string
secondList []int
minuteList []int
hourList []int
@ -74,14 +73,15 @@ func NewCronExpression(cronLine string) *CronExpression {
copy(cronFields[1:], cronFields[0:])
cronFields[0] = "0"
}
// We should have 7 fields at this point
if len(cronFields) != 7 {
// At this point, we should have at least 7 fields. Fields beyond the
// seventh one, if any, are ignored.
if len(cronFields) < 7 {
panic("Malformed cron expression\n")
}
// Generic parser can be used for most fields
cronExpr := &CronExpression{
Expression: cronLine,
expression: cronLine,
secondList: genericFieldParse(cronFields[0], 0, 59),
minuteList: genericFieldParse(cronFields[1], 0, 59),
hourList: genericFieldParse(cronFields[2], 0, 23),
@ -101,12 +101,9 @@ func NewCronExpression(cronLine string) *CronExpression {
/******************************************************************************/
// NextTime() returns the time stamp following fromTime which
// satisfies the cron expression cronLine. If no matching time stamp is found,
// using NoMatch() with the returned time stamp as argument will return true.
//
// If the same cron expression must be used repeatedly, it is better to use
// NewCronExpression() in order to avoid overhead of cron expression parsing.
// Given a time stamp `fromTime`, return the closest following time stamp
// which matches the cron expression string .. `cronLine`. The `time.Location`
// of the returned time stamp is the same as `fromTime`.
func NextTime(cronLine string, fromTime time.Time) time.Time {
cronexpr := NewCronExpression(cronLine)
return cronexpr.NextTime(fromTime)
@ -114,12 +111,10 @@ func NextTime(cronLine string, fromTime time.Time) time.Time {
/******************************************************************************/
// NextTimeN() returns the n time stamps following fromTime which
// satisfy the cron expression cronLine. An empty list is returned if
// there is no matching time stamp.
//
// If the same cron expression must be used repeatedly, it is better to use
// NewCronExpression() in order to avoid overhead of cron expression parsing.
// Given a time stamp `fromTime`, return a slice of `n` closest following time
// stamps which match the cron expression string `cronLine`. The time stamps in
// the returned slice are in chronological ascending order. The `time.Location`
// of the returned time stamps is the same as `fromTime`.
func NextTimeN(cronLine string, fromTime time.Time, n int) []time.Time {
cronexpr := NewCronExpression(cronLine)
return cronexpr.NextTimeN(fromTime, n)
@ -127,9 +122,9 @@ func NextTimeN(cronLine string, fromTime time.Time, n int) []time.Time {
/******************************************************************************/
// CronExpression.NextTime() returns the time stamp following fromTime which
// satisfies the cron expression. If no matching time stamp is found,
// using NoMatch() with the returned time stamp as argument will return true.
// Given a time stamp `fromTime`, return the closest following time stamp which
// matches the cron expression `cronexpr`. The `time.Location` of the returned
// time stamp is the same as `fromTime`.
func (cronexpr *CronExpression) NextTime(fromTime time.Time) time.Time {
// Special case
if NoMatch(fromTime) {
@ -212,9 +207,10 @@ func (cronexpr *CronExpression) NextTime(fromTime time.Time) time.Time {
/******************************************************************************/
// CronExpression.NextTimeN() returns an array of n time stamps following
// fromTime which satisfy the cron expression. An empty list is returned if
// there is no matching time stamp.
// Given a time stamp `fromTime`, return a slice of `n` closest following time
// stamps which match the cron expression `cronexpr`. The time stamps in the
// returned slice are in chronological ascending order. The `time.Location` of
// the returned time stamps is the same as `fromTime`.
func (cronexpr *CronExpression) NextTimeN(fromTime time.Time, n int) []time.Time {
if n <= 0 {
panic("CronExpression.NextTimeN(): invalid count")
@ -237,8 +233,10 @@ func (cronexpr *CronExpression) NextTimeN(fromTime time.Time, n int) []time.Time
/******************************************************************************/
// NoMatch() returns whether t is a valid time stamp, from CronExpression point
// of view.
// Returns `true` if time stamp `t` is not a valid time stamp from
// `CronExpression` point of view. An invalid time stamp is returned by this
// library whenever no matching time stamp is found given a specific cron
// expression.
func NoMatch(t time.Time) bool {
// https://en.wikipedia.org/wiki/Cron#CRON_expression: 1970–2099
return t.Year() >= 2100