325 lines
7.0 KiB
Go
325 lines
7.0 KiB
Go
package strftime
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import (
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"bytes"
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"strconv"
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"time"
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)
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// Format returns a textual representation of the time value
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// formatted according to the strftime format specification.
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func Format(fmt string, t time.Time) string {
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buf := buffer(fmt)
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return string(AppendFormat(buf, fmt, t))
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}
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// AppendFormat is like Format, but appends the textual representation
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// to dst and returns the extended buffer.
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func AppendFormat(dst []byte, fmt string, t time.Time) []byte {
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var parser parser
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parser.literal = func(b byte) error {
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dst = append(dst, b)
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return nil
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}
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parser.format = func(spec, flag byte) error {
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switch spec {
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case 'A':
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dst = append(dst, t.Weekday().String()...)
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return nil
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case 'a':
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dst = append(dst, t.Weekday().String()[:3]...)
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return nil
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case 'B':
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dst = append(dst, t.Month().String()...)
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return nil
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case 'b', 'h':
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dst = append(dst, t.Month().String()[:3]...)
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return nil
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case 'm':
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dst = appendInt2(dst, int(t.Month()), flag)
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return nil
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case 'd':
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dst = appendInt2(dst, int(t.Day()), flag)
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return nil
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case 'e':
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dst = appendInt2(dst, int(t.Day()), ' ')
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return nil
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case 'I':
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dst = append12Hour(dst, t, flag)
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return nil
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case 'l':
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dst = append12Hour(dst, t, ' ')
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return nil
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case 'H':
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dst = appendInt2(dst, t.Hour(), flag)
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return nil
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case 'k':
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dst = appendInt2(dst, t.Hour(), ' ')
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return nil
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case 'M':
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dst = appendInt2(dst, t.Minute(), flag)
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return nil
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case 'S':
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dst = appendInt2(dst, t.Second(), flag)
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return nil
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case 'L':
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dst = append(dst, t.Format(".000")[1:]...)
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return nil
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case 'f':
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dst = append(dst, t.Format(".000000")[1:]...)
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return nil
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case 'N':
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dst = append(dst, t.Format(".000000000")[1:]...)
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return nil
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case 'y':
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dst = t.AppendFormat(dst, "06")
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return nil
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case 'Y':
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dst = t.AppendFormat(dst, "2006")
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return nil
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case 'C':
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dst = t.AppendFormat(dst, "2006")
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dst = dst[:len(dst)-2]
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return nil
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case 'U':
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dst = appendWeekNumber(dst, t, flag, true)
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return nil
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case 'W':
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dst = appendWeekNumber(dst, t, flag, false)
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return nil
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case 'V':
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_, w := t.ISOWeek()
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dst = appendInt2(dst, w, flag)
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return nil
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case 'g':
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y, _ := t.ISOWeek()
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dst = year(y).AppendFormat(dst, "06")
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return nil
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case 'G':
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y, _ := t.ISOWeek()
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dst = year(y).AppendFormat(dst, "2006")
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return nil
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case 's':
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dst = strconv.AppendInt(dst, t.Unix(), 10)
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return nil
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case 'Q':
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dst = strconv.AppendInt(dst, t.UnixMilli(), 10)
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return nil
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case 'w':
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w := t.Weekday()
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dst = appendInt1(dst, int(w))
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return nil
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case 'u':
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if w := t.Weekday(); w == 0 {
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dst = append(dst, '7')
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} else {
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dst = appendInt1(dst, int(w))
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}
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return nil
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case 'j':
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if flag == '-' {
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dst = strconv.AppendInt(dst, int64(t.YearDay()), 10)
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} else {
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dst = t.AppendFormat(dst, "002")
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}
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return nil
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}
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if layout := goLayout(spec, flag, false); layout != "" {
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dst = t.AppendFormat(dst, layout)
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return nil
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}
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dst = append(dst, '%')
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if flag != 0 {
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dst = append(dst, flag)
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}
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dst = append(dst, spec)
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return nil
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}
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parser.parse(fmt)
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return dst
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}
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// Parse converts a textual representation of time to the time value it represents
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// according to the strptime format specification.
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func Parse(fmt, value string) (time.Time, error) {
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pattern, err := layout(fmt, true)
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if err != nil {
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return time.Time{}, err
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}
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return time.Parse(pattern, value)
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}
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// Layout converts a strftime format specification
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// to a Go time pattern specification.
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func Layout(fmt string) (string, error) {
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return layout(fmt, false)
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}
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func layout(fmt string, parsing bool) (string, error) {
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dst := buffer(fmt)
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var parser parser
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parser.literal = func(b byte) error {
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if '0' <= b && b <= '9' {
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return literalErr(b)
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}
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dst = append(dst, b)
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if b == 'M' || b == 'T' || b == 'm' || b == 'n' {
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switch {
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case bytes.HasSuffix(dst, []byte("Jan")):
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return literalErr("Jan")
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case bytes.HasSuffix(dst, []byte("Mon")):
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return literalErr("Mon")
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case bytes.HasSuffix(dst, []byte("MST")):
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return literalErr("MST")
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case bytes.HasSuffix(dst, []byte("PM")):
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return literalErr("PM")
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case bytes.HasSuffix(dst, []byte("pm")):
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return literalErr("pm")
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}
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}
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return nil
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}
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parser.format = func(spec, flag byte) error {
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if layout := goLayout(spec, flag, parsing); layout != "" {
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dst = append(dst, layout...)
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return nil
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}
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switch spec {
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default:
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return formatError{}
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case 'L', 'f', 'N':
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if bytes.HasSuffix(dst, []byte(".")) || bytes.HasSuffix(dst, []byte(",")) {
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switch spec {
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default:
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dst = append(dst, "000"...)
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case 'f':
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dst = append(dst, "000000"...)
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case 'N':
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dst = append(dst, "000000000"...)
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}
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return nil
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}
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return formatError{message: "must follow '.' or ','"}
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}
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}
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if err := parser.parse(fmt); err != nil {
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return "", err
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}
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return string(dst), nil
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}
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// UTS35 converts a strftime format specification
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// to a Unicode Technical Standard #35 Date Format Pattern.
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func UTS35(fmt string) (string, error) {
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const quote = '\''
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var quoted bool
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dst := buffer(fmt)
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var parser parser
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parser.literal = func(b byte) error {
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if b == quote {
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dst = append(dst, quote, quote)
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return nil
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}
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if !quoted && ('a' <= b && b <= 'z' || 'A' <= b && b <= 'Z') {
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dst = append(dst, quote)
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quoted = true
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}
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dst = append(dst, b)
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return nil
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}
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parser.format = func(spec, flag byte) error {
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if quoted {
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dst = append(dst, quote)
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quoted = false
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}
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if pattern := uts35Pattern(spec, flag); pattern != "" {
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dst = append(dst, pattern...)
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return nil
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}
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return formatError{}
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}
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if err := parser.parse(fmt); err != nil {
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return "", err
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}
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if quoted {
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dst = append(dst, quote)
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}
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return string(dst), nil
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}
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func buffer(format string) (buf []byte) {
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const bufSize = 64
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max := len(format) + 10
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if max < bufSize {
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var b [bufSize]byte
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buf = b[:0]
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} else {
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buf = make([]byte, 0, max)
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}
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return
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}
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func year(y int) time.Time {
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return time.Date(y, time.January, 1, 0, 0, 0, 0, time.UTC)
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}
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func appendWeekNumber(dst []byte, t time.Time, flag byte, sunday bool) []byte {
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offset := int(t.Weekday())
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if sunday {
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offset = 6 - offset
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} else if offset != 0 {
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offset = 7 - offset
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}
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return appendInt2(dst, (t.YearDay()+offset)/7, flag)
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}
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func append12Hour(dst []byte, t time.Time, flag byte) []byte {
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h := t.Hour()
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if h == 0 {
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h = 12
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} else if h > 12 {
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h -= 12
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}
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return appendInt2(dst, h, flag)
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}
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func appendInt1(dst []byte, i int) []byte {
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return append(dst, byte('0'+i))
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}
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func appendInt2(dst []byte, i int, flag byte) []byte {
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if flag == 0 || i >= 10 {
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return append(dst, smallsString[i*2:i*2+2]...)
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}
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if flag == ' ' {
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dst = append(dst, flag)
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}
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return appendInt1(dst, i)
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}
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const smallsString = "" +
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"00010203040506070809" +
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"10111213141516171819" +
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"20212223242526272829" +
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"30313233343536373839" +
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"40414243444546474849" +
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"50515253545556575859" +
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"60616263646566676869" +
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"70717273747576777879" +
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"80818283848586878889" +
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"90919293949596979899"
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