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package ber
import (
"bytes"
"errors"
"fmt"
"strconv"
"time"
)
// ErrInvalidTimeFormat is returned when the generalizedTime string was not correct.
var ErrInvalidTimeFormat = errors.New("invalid time format")
var zeroTime = time.Time{}
// ParseGeneralizedTime parses a string value and if it conforms to
// GeneralizedTime[^0] format, will return a time.Time for that value.
//
// [^0]: https://www.itu.int/rec/T-REC-X.690-201508-I/en Section 11.7
func ParseGeneralizedTime(v []byte) (time.Time, error) {
var format string
var fract time.Duration
str := []byte(DecodeString(v))
tzIndex := bytes.IndexAny(str, "Z+-")
if tzIndex < 0 {
return zeroTime, ErrInvalidTimeFormat
}
dot := bytes.IndexAny(str, ".,")
switch dot {
case -1:
switch tzIndex {
case 10:
format = `2006010215Z`
case 12:
format = `200601021504Z`
case 14:
format = `20060102150405Z`
default:
return zeroTime, ErrInvalidTimeFormat
}
case 10, 12:
if tzIndex < dot {
return zeroTime, ErrInvalidTimeFormat
}
// a "," is also allowed, but would not be parsed by time.Parse():
str[dot] = '.'
// If <minute> is omitted, then <fraction> represents a fraction of an
// hour; otherwise, if <second> and <leap-second> are omitted, then
// <fraction> represents a fraction of a minute; otherwise, <fraction>
// represents a fraction of a second.
// parse as float from dot to timezone
f, err := strconv.ParseFloat(string(str[dot:tzIndex]), 64)
if err != nil {
return zeroTime, fmt.Errorf("failed to parse float: %s", err)
}
// ...and strip that part
str = append(str[:dot], str[tzIndex:]...)
tzIndex = dot
if dot == 10 {
fract = time.Duration(int64(f * float64(time.Hour)))
format = `2006010215Z`
} else {
fract = time.Duration(int64(f * float64(time.Minute)))
format = `200601021504Z`
}
case 14:
if tzIndex < dot {
return zeroTime, ErrInvalidTimeFormat
}
str[dot] = '.'
// no need for fractional seconds, time.Parse() handles that
format = `20060102150405Z`
default:
return zeroTime, ErrInvalidTimeFormat
}
l := len(str)
switch l - tzIndex {
case 1:
if str[l-1] != 'Z' {
return zeroTime, ErrInvalidTimeFormat
}
case 3:
format += `0700`
str = append(str, []byte("00")...)
case 5:
format += `0700`
default:
return zeroTime, ErrInvalidTimeFormat
}
t, err := time.Parse(format, string(str))
if err != nil {
return zeroTime, fmt.Errorf("%s: %s", ErrInvalidTimeFormat, err)
}
return t.Add(fract), nil
}
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