Add dedicated ISO 8601 parser.

core/time/iso8061.odin

@@ -0,0 +1,113 @@
+package time
+// Parsing ISO 8601 date/time strings into time.Time.
+
+import dt "core:time/datetime"
+
+// Parses an ISO 8601 string and returns Time in UTC, with any UTC offset applied to it.
+// Only 4-digit years are accepted.
+// Optional pointer to boolean `is_leap` will return `true` if the moment was a leap second.
+// Leap seconds are smeared into 23:59:59.
+iso8601_to_time_utc :: proc(iso_datetime: string, is_leap: ^bool = nil) -> (res: Time, consumed: int) {
+	offset: int
+
+	res, offset, consumed = iso8601_to_time_and_offset(iso_datetime, is_leap)
+	res._nsec += (i64(-offset) * i64(Minute))
+	return res, consumed
+}
+
+// Parses an ISO 8601 string and returns Time and a UTC offset in minutes.
+// e.g. 1985-04-12T23:20:50.52Z
+// Note: Only 4-digit years are accepted.
+// Optional pointer to boolean `is_leap` will return `true` if the moment was a leap second.
+// Leap seconds are smeared into 23:59:59.
+iso8601_to_time_and_offset :: proc(iso_datetime: string, is_leap: ^bool = nil) -> (res: Time, utc_offset: int, consumed: int) {
+	moment, offset, leap_second, count := iso8601_to_components(iso_datetime)
+	if count == 0 {
+		return
+	}
+
+	if is_leap != nil {
+		is_leap^ = leap_second
+	}
+
+	if _res, ok := datetime_to_time(moment.year, moment.month, moment.day, moment.hour, moment.minute, moment.second, moment.nano); !ok {
+		return {}, 0, 0
+	} else {
+		return _res, offset, count
+	}
+}
+
+// Parses an ISO 8601 string and returns Time and a UTC offset in minutes.
+// e.g. 1985-04-12T23:20:50.52Z
+// Performs no validation on whether components are valid, e.g. it'll return hour = 25 if that's what it's given
+iso8601_to_components :: proc(iso_datetime: string) -> (res: dt.DateTime, utc_offset: int, is_leap: bool, consumed: int) {
+	moment, offset, count, leap_second, ok := _iso8601_to_components(iso_datetime)
+	if !ok {
+		return
+	}
+	return moment, offset, leap_second, count
+}
+
+// Parses an ISO 8601 string and returns datetime.DateTime.
+// Performs no validation on whether components are valid, e.g. it'll return hour = 25 if that's what it's given
+@(private)
+_iso8601_to_components :: proc(iso_datetime: string) -> (res: dt.DateTime, utc_offset: int, consumed: int, is_leap: bool, ok: bool) {
+	// A compliant date is at minimum 20 characters long, e.g. YYYY-MM-DDThh:mm:ssZ
+	(len(iso_datetime) >= 20) or_return
+
+	// Scan and eat YYYY-MM-DD[Tt], then scan and eat HH:MM:SS, leave separator
+	year   := scan_digits(iso_datetime[0:], "-",   4) or_return
+	month  := scan_digits(iso_datetime[5:], "-",   2) or_return
+	day    := scan_digits(iso_datetime[8:], "Tt ", 2) or_return
+	hour   := scan_digits(iso_datetime[11:], ":",  2) or_return
+	minute := scan_digits(iso_datetime[14:], ":",  2) or_return
+	second := scan_digits(iso_datetime[17:], "",   2) or_return
+	nanos  := 0
+	count  := 19
+
+	// Scan fractional seconds
+	if iso_datetime[count] == '.' {
+		count += 1 // consume '.'
+		multiplier := 100_000_000
+		for digit in iso_datetime[count:] {
+			if int(digit) >= '0' && int(digit) <= '9' {
+				nanos += int(digit - '0') * multiplier
+				multiplier /= 10
+				count += 1
+			} else {
+				break
+			}
+		}
+	}
+
+	// Leap second handling
+	if minute == 59 && second == 60 {
+		second = 59
+		is_leap = true
+	}
+
+	err: dt.Error
+	if res, err = dt.components_to_datetime(year, month, day, hour, minute, second, nanos); err != .None {
+		return {}, 0, 0, false, false
+	}
+
+	if len(iso_datetime[count:]) == 0 {
+		return res, utc_offset, count, is_leap, true
+	}
+
+	// Scan UTC offset
+	switch iso_datetime[count] {
+	case 'Z', 'z':
+		utc_offset = 0
+		count += 1
+	case '+', '-':
+		(len(iso_datetime[count:]) >= 6) or_return
+		offset_hour   := scan_digits(iso_datetime[count+1:], ":", 2) or_return
+		offset_minute := scan_digits(iso_datetime[count+4:], "",  2) or_return
+
+		utc_offset = 60 * offset_hour + offset_minute
+		utc_offset *= -1 if iso_datetime[count] == '-' else 1
+		count += 6
+	}
+	return res, utc_offset, count, is_leap, true
+}