Code to parse ISO8601 timestamps at least semi-robustly
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Kovid Goyal
parent
64cb9c9542
commit
c113ad6f56
166
tools/utils/iso8601.go
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166
tools/utils/iso8601.go
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// License: GPLv3 Copyright: 2023, Kovid Goyal, <kovid at kovidgoyal.net>
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package utils
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import (
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"fmt"
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"strconv"
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"strings"
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"time"
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)
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var _ = fmt.Print
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func is_digit(x byte) bool {
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return '0' <= x && x <= '9'
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}
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// The following is copied from the Go standard library to implement date range validation logic
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// equivalent to the behaviour of Go's time.Parse.
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func isLeap(year int) bool {
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return year%4 == 0 && (year%100 != 0 || year%400 == 0)
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}
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// daysInMonth is the number of days for non-leap years in each calendar month starting at 1
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var daysInMonth = [13]int{0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
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func daysIn(m time.Month, year int) int {
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if m == time.February && isLeap(year) {
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return 29
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}
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return daysInMonth[int(m)]
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}
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func ISO8601Parse(raw string) (time.Time, error) {
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orig := raw
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raw = strings.TrimSpace(raw)
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required_number := func(num_digits int) (int, error) {
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if len(raw) < num_digits {
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return 0, fmt.Errorf("Insufficient digits")
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}
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text := raw[:num_digits]
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raw = raw[num_digits:]
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ans, err := strconv.ParseUint(text, 10, 32)
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return int(ans), err
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}
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optional_separator := func(x byte) bool {
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if len(raw) > 0 && raw[0] == x {
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raw = raw[1:]
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}
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return len(raw) > 0 && is_digit(raw[0])
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}
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errf := func(msg string) (time.Time, error) {
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return time.Time{}, fmt.Errorf("Invalid ISO8601 timestamp: %#v. %s", orig, msg)
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}
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optional_separator('+')
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year, err := required_number(4)
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if err != nil {
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return errf("timestamp does not start with a 4 digit year")
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}
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var month int = 1
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var day int = 1
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if optional_separator('-') {
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month, err = required_number(2)
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if err != nil {
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return errf("timestamp does not have a valid 2 digit month")
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}
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if optional_separator('-') {
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day, err = required_number(2)
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if err != nil {
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return errf("timestamp does not have a valid 2 digit day")
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}
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}
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}
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var hour, minute, second, nsec int
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if len(raw) > 0 && (raw[0] == 'T' || raw[0] == ' ') {
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raw = raw[1:]
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hour, err = required_number(2)
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if err != nil {
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return errf("timestamp does not have a valid 2 digit hour")
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}
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if optional_separator(':') {
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minute, err = required_number(2)
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if err != nil {
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return errf("timestamp does not have a valid 2 digit minute")
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}
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if optional_separator(':') {
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second, err = required_number(2)
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if err != nil {
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return errf("timestamp does not have a valid 2 digit second")
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}
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}
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}
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if len(raw) > 0 && (raw[0] == '.' || raw[0] == ',') {
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raw = raw[1:]
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num_digits := 0
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for len(raw) > num_digits && is_digit(raw[num_digits]) {
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num_digits++
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}
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text := raw[:num_digits]
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raw = raw[num_digits:]
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extra := 9 - len(text)
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if extra < 0 {
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text = text[:9]
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}
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if text != "" {
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n, err := strconv.ParseUint(text, 10, 64)
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if err != nil {
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return errf("timestamp does not have a valid nanosecond field")
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}
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nsec = int(n)
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for ; extra > 0; extra-- {
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nsec *= 10
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}
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}
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}
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}
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switch {
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case month < 1 || month > 12:
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return errf("timestamp has invalid month value")
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case day < 1 || day > 31 || day > daysIn(time.Month(month), year):
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return errf("timestamp has invalid day value")
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case hour < 0 || hour > 23:
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return errf("timestamp has invalid hour value")
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case minute < 0 || minute > 59:
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return errf("timestamp has invalid minute value")
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case second < 0 || second > 59:
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return errf("timestamp has invalid second value")
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}
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loc := time.UTC
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tzsign, tzhour, tzminute := 0, 0, 0
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if len(raw) > 0 {
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switch raw[0] {
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case '+':
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tzsign = 1
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case '-':
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tzsign = -1
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}
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}
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if tzsign != 0 {
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raw = raw[1:]
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tzhour, err = required_number(2)
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if err != nil {
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return errf("timestamp has invalid timezone hour")
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}
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optional_separator(':')
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tzminute, err = required_number(2)
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if err != nil {
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tzminute = 0
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}
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seconds := tzhour*3600 + tzminute*60
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loc = time.FixedZone("", tzsign*seconds)
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}
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return time.Date(year, time.Month(month), day, hour, minute, second, nsec, loc), err
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}
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func ISO8601Format(x time.Time) string {
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return x.Format(time.RFC3339Nano)
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}
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40
tools/utils/iso8601_test.go
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40
tools/utils/iso8601_test.go
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@ -0,0 +1,40 @@
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// License: GPLv3 Copyright: 2023, Kovid Goyal, <kovid at kovidgoyal.net>
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package utils
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import (
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"fmt"
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"testing"
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"time"
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"github.com/google/go-cmp/cmp"
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)
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var _ = fmt.Print
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func TestISO8601(t *testing.T) {
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now := time.Now()
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tt := func(raw string, expected time.Time) {
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actual, err := ISO8601Parse(raw)
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if err != nil {
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t.Fatalf("Parsing: %#v failed with error: %s", raw, err)
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}
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if diff := cmp.Diff(expected, actual); diff != "" {
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t.Fatalf("Parsing: %#v failed:\n%s", raw, diff)
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}
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}
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tt(ISO8601Format(now), now)
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tt("2023-02-08T07:24:09.551975+00:00", time.Date(2023, 2, 8, 7, 24, 9, 551975000, time.UTC))
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tt("2023-02-08T07:24:09.551975Z", time.Date(2023, 2, 8, 7, 24, 9, 551975000, time.UTC))
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tt("2023", time.Date(2023, 1, 1, 0, 0, 0, 0, time.UTC))
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tt("2023-11-13", time.Date(2023, 11, 13, 0, 0, 0, 0, time.UTC))
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tt("2023-11-13 07:23", time.Date(2023, 11, 13, 7, 23, 0, 0, time.UTC))
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tt("2023-11-13 07:23:01", time.Date(2023, 11, 13, 7, 23, 1, 0, time.UTC))
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tt("2023-11-13 07:23:01.", time.Date(2023, 11, 13, 7, 23, 1, 0, time.UTC))
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tt("2023-11-13 07:23:01.0", time.Date(2023, 11, 13, 7, 23, 1, 0, time.UTC))
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tt("2023-11-13 07:23:01.1", time.Date(2023, 11, 13, 7, 23, 1, 100000000, time.UTC))
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tt("202311-13 07", time.Date(2023, 11, 13, 7, 0, 0, 0, time.UTC))
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tt("20231113 0705", time.Date(2023, 11, 13, 7, 5, 0, 0, time.UTC))
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}
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