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ladybird/Userland/Libraries/LibCore/DateTime.cpp
Timothy Flynn 672a555f98 LibCore+LibJS+LibUnicode: Port retrieving time zone offsets to ICU 
The changes to tests are due to LibTimeZone incorrectly interpreting
time stamps in the TZDB. The TZDB will list zone transitions in either
UTC or the zone's local time (which is then subject to DST offsets).
LibTimeZone did not handle the latter at all.

For example:

The following rule is in effect until November 18, 6PM UTC.

    America/Chicago -5:50:36 - LMT 1883 Nov 18 18:00u

The following rule is in effect until March 1, 2AM in Chicago time. But
at that time, a DST transition occurs, so the local time is actually
3AM.

    America/Chicago -6:00 Chicago C%sT 1936 Mar 1 2:00
2024-06-26 10:14:02 +02:00

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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/CharacterTypes.h>
#include <AK/DateConstants.h>
#include <AK/GenericLexer.h>
#include <AK/String.h>
#include <AK/StringBuilder.h>
#include <AK/Time.h>
#include <LibCore/DateTime.h>
#include <LibUnicode/TimeZone.h>
#include <errno.h>
#include <time.h>
namespace Core {
static Optional<StringView> parse_time_zone_name(GenericLexer& lexer)
{
auto const& time_zones = Unicode::available_time_zones();
auto start_position = lexer.tell();
Optional<StringView> canonicalized_time_zone;
lexer.ignore_until([&](auto) {
auto time_zone = lexer.input().substring_view(start_position, lexer.tell() - start_position + 1);
auto it = time_zones.find_if([&](auto const& candidate) { return time_zone.equals_ignoring_ascii_case(candidate); });
if (it == time_zones.end())
return false;
canonicalized_time_zone = *it;
return true;
});
if (canonicalized_time_zone.has_value())
lexer.ignore();
return canonicalized_time_zone;
}
static void apply_time_zone_offset(StringView time_zone, UnixDateTime& time)
{
if (auto offset = Unicode::time_zone_offset(time_zone, time); offset.has_value())
time -= offset->offset;
}
DateTime DateTime::now()
{
return from_timestamp(time(nullptr));
}
DateTime DateTime::create(int year, int month, int day, int hour, int minute, int second)
{
DateTime dt;
dt.set_time(year, month, day, hour, minute, second);
return dt;
}
DateTime DateTime::from_timestamp(time_t timestamp)
{
struct tm tm;
localtime_r(&timestamp, &tm);
DateTime dt;
dt.m_year = tm.tm_year + 1900;
dt.m_month = tm.tm_mon + 1;
dt.m_day = tm.tm_mday;
dt.m_hour = tm.tm_hour;
dt.m_minute = tm.tm_min;
dt.m_second = tm.tm_sec;
dt.m_timestamp = timestamp;
return dt;
}
unsigned DateTime::weekday() const
{
return ::day_of_week(m_year, m_month, m_day);
}
unsigned DateTime::days_in_month() const
{
return ::days_in_month(m_year, m_month);
}
unsigned DateTime::day_of_year() const
{
return ::day_of_year(m_year, m_month, m_day);
}
bool DateTime::is_leap_year() const
{
return ::is_leap_year(m_year);
}
void DateTime::set_time(int year, int month, int day, int hour, int minute, int second)
{
struct tm tm = {};
tm.tm_sec = second;
tm.tm_min = minute;
tm.tm_hour = hour;
tm.tm_mday = day;
tm.tm_mon = month - 1;
tm.tm_year = year - 1900;
tm.tm_isdst = -1;
// mktime() doesn't read tm.tm_wday and tm.tm_yday, no need to fill them in.
m_timestamp = mktime(&tm);
// mktime() normalizes the components to the right ranges (Jan 32 -> Feb 1 etc), so read fields back out from tm.
m_year = tm.tm_year + 1900;
m_month = tm.tm_mon + 1;
m_day = tm.tm_mday;
m_hour = tm.tm_hour;
m_minute = tm.tm_min;
m_second = tm.tm_sec;
}
void DateTime::set_time_only(int hour, int minute, Optional<int> second)
{
set_time(year(), month(), day(), hour, minute, second.has_value() ? second.release_value() : this->second());
}
void DateTime::set_date(Core::DateTime const& other)
{
set_time(other.year(), other.month(), other.day(), hour(), minute(), second());
}
ErrorOr<String> DateTime::to_string(StringView format, LocalTime local_time) const
{
struct tm tm;
if (local_time == LocalTime::Yes)
localtime_r(&m_timestamp, &tm);
else
gmtime_r(&m_timestamp, &tm);
StringBuilder builder;
size_t const format_len = format.length();
auto format_time_zone_offset = [&](bool with_separator) -> ErrorOr<void> {
struct tm gmt_tm;
gmtime_r(&m_timestamp, &gmt_tm);
gmt_tm.tm_isdst = -1;
auto gmt_timestamp = mktime(&gmt_tm);
auto offset_seconds = static_cast<time_t>(difftime(m_timestamp, gmt_timestamp));
StringView offset_sign;
if (offset_seconds >= 0) {
offset_sign = "+"sv;
} else {
offset_sign = "-"sv;
offset_seconds *= -1;
}
auto offset_hours = offset_seconds / 3600;
auto offset_minutes = (offset_seconds % 3600) / 60;
auto separator = with_separator ? ":"sv : ""sv;
TRY(builder.try_appendff("{}{:02}{}{:02}", offset_sign, offset_hours, separator, offset_minutes));
return {};
};
for (size_t i = 0; i < format_len; ++i) {
if (format[i] != '%') {
TRY(builder.try_append(format[i]));
} else {
if (++i == format_len)
return String {};
switch (format[i]) {
case 'a':
TRY(builder.try_append(short_day_names[tm.tm_wday]));
break;
case 'A':
TRY(builder.try_append(long_day_names[tm.tm_wday]));
break;
case 'b':
TRY(builder.try_append(short_month_names[tm.tm_mon]));
break;
case 'B':
TRY(builder.try_append(long_month_names[tm.tm_mon]));
break;
case 'C':
TRY(builder.try_appendff("{:02}", (tm.tm_year + 1900) / 100));
break;
case 'd':
TRY(builder.try_appendff("{:02}", tm.tm_mday));
break;
case 'D':
TRY(builder.try_appendff("{:02}/{:02}/{:02}", tm.tm_mon + 1, tm.tm_mday, (tm.tm_year + 1900) % 100));
break;
case 'e':
TRY(builder.try_appendff("{:2}", tm.tm_mday));
break;
case 'h':
TRY(builder.try_append(short_month_names[tm.tm_mon]));
break;
case 'H':
TRY(builder.try_appendff("{:02}", tm.tm_hour));
break;
case 'I': {
int display_hour = tm.tm_hour % 12;
if (display_hour == 0)
display_hour = 12;
TRY(builder.try_appendff("{:02}", display_hour));
break;
}
case 'j':
TRY(builder.try_appendff("{:03}", tm.tm_yday + 1));
break;
case 'l': {
int display_hour = tm.tm_hour % 12;
if (display_hour == 0)
display_hour = 12;
TRY(builder.try_appendff("{:2}", display_hour));
break;
}
case 'm':
TRY(builder.try_appendff("{:02}", tm.tm_mon + 1));
break;
case 'M':
TRY(builder.try_appendff("{:02}", tm.tm_min));
break;
case 'n':
TRY(builder.try_append('\n'));
break;
case 'p':
TRY(builder.try_append(tm.tm_hour < 12 ? "AM"sv : "PM"sv));
break;
case 'r': {
int display_hour = tm.tm_hour % 12;
if (display_hour == 0)
display_hour = 12;
TRY(builder.try_appendff("{:02}:{:02}:{:02} {}", display_hour, tm.tm_min, tm.tm_sec, tm.tm_hour < 12 ? "AM" : "PM"));
break;
}
case 'R':
TRY(builder.try_appendff("{:02}:{:02}", tm.tm_hour, tm.tm_min));
break;
case 'S':
TRY(builder.try_appendff("{:02}", tm.tm_sec));
break;
case 't':
TRY(builder.try_append('\t'));
break;
case 'T':
TRY(builder.try_appendff("{:02}:{:02}:{:02}", tm.tm_hour, tm.tm_min, tm.tm_sec));
break;
case 'u':
TRY(builder.try_appendff("{}", tm.tm_wday ? tm.tm_wday : 7));
break;
case 'U': {
int const wday_of_year_beginning = (tm.tm_wday + 6 * tm.tm_yday) % 7;
int const week_number = (tm.tm_yday + wday_of_year_beginning) / 7;
TRY(builder.try_appendff("{:02}", week_number));
break;
}
case 'V': {
int const wday_of_year_beginning = (tm.tm_wday + 6 + 6 * tm.tm_yday) % 7;
int week_number = (tm.tm_yday + wday_of_year_beginning) / 7 + 1;
if (wday_of_year_beginning > 3) {
if (tm.tm_yday >= 7 - wday_of_year_beginning)
--week_number;
else {
int const days_of_last_year = days_in_year(tm.tm_year + 1900 - 1);
int const wday_of_last_year_beginning = (wday_of_year_beginning + 6 * days_of_last_year) % 7;
week_number = (days_of_last_year + wday_of_last_year_beginning) / 7 + 1;
if (wday_of_last_year_beginning > 3)
--week_number;
}
}
TRY(builder.try_appendff("{:02}", week_number));
break;
}
case 'w':
TRY(builder.try_appendff("{}", tm.tm_wday));
break;
case 'W': {
int const wday_of_year_beginning = (tm.tm_wday + 6 + 6 * tm.tm_yday) % 7;
int const week_number = (tm.tm_yday + wday_of_year_beginning) / 7;
TRY(builder.try_appendff("{:02}", week_number));
break;
}
case 'y':
TRY(builder.try_appendff("{:02}", (tm.tm_year + 1900) % 100));
break;
case 'Y':
TRY(builder.try_appendff("{}", tm.tm_year + 1900));
break;
case 'z':
TRY(format_time_zone_offset(false));
break;
case ':':
if (++i == format_len) {
TRY(builder.try_append("%:"sv));
break;
}
if (format[i] != 'z') {
TRY(builder.try_append("%:"sv));
TRY(builder.try_append(format[i]));
break;
}
TRY(format_time_zone_offset(true));
break;
case 'Z': {
auto const* timezone_name = tzname[tm.tm_isdst == 0 ? 0 : 1];
TRY(builder.try_append({ timezone_name, strlen(timezone_name) }));
break;
}
case '%':
TRY(builder.try_append('%'));
break;
default:
TRY(builder.try_append('%'));
TRY(builder.try_append(format[i]));
break;
}
}
}
return builder.to_string();
}
ByteString DateTime::to_byte_string(StringView format, LocalTime local_time) const
{
return MUST(to_string(format, local_time)).to_byte_string();
}
Optional<DateTime> DateTime::parse(StringView format, StringView string)
{
unsigned format_pos = 0;
struct tm tm = {};
tm.tm_isdst = -1;
auto parsing_failed = false;
auto tm_represents_utc_time = false;
Optional<StringView> parsed_time_zone;
GenericLexer string_lexer(string);
auto parse_number = [&] {
auto result = string_lexer.consume_decimal_integer<int>();
if (result.is_error()) {
parsing_failed = true;
return 0;
}
return result.value();
};
auto consume = [&](char c) {
if (!string_lexer.consume_specific(c))
parsing_failed = true;
};
auto consume_specific_ascii_case_insensitive = [&](StringView name) {
auto next_string = string_lexer.peek_string(name.length());
if (next_string.has_value() && next_string->equals_ignoring_ascii_case(name)) {
string_lexer.consume(name.length());
return true;
}
return false;
};
while (format_pos < format.length() && !string_lexer.is_eof()) {
if (format[format_pos] != '%') {
consume(format[format_pos]);
format_pos++;
continue;
}
format_pos++;
if (format_pos == format.length())
return {};
switch (format[format_pos]) {
case 'a': {
auto wday = 0;
for (auto name : short_day_names) {
if (consume_specific_ascii_case_insensitive(name)) {
tm.tm_wday = wday;
break;
}
++wday;
}
if (wday == 7)
return {};
break;
}
case 'A': {
auto wday = 0;
for (auto name : long_day_names) {
if (consume_specific_ascii_case_insensitive(name)) {
tm.tm_wday = wday;
break;
}
++wday;
}
if (wday == 7)
return {};
break;
}
case 'h':
case 'b': {
auto mon = 0;
for (auto name : short_month_names) {
if (consume_specific_ascii_case_insensitive(name)) {
tm.tm_mon = mon;
break;
}
++mon;
}
if (mon == 12)
return {};
break;
}
case 'B': {
auto mon = 0;
for (auto name : long_month_names) {
if (consume_specific_ascii_case_insensitive(name)) {
tm.tm_mon = mon;
break;
}
++mon;
}
if (mon == 12)
return {};
break;
}
case 'C': {
int num = parse_number();
tm.tm_year = (num - 19) * 100;
break;
}
case 'd':
tm.tm_mday = parse_number();
break;
case 'D': {
int mon = parse_number();
consume('/');
int day = parse_number();
consume('/');
int year = parse_number();
tm.tm_mon = mon + 1;
tm.tm_mday = day;
tm.tm_year = (year + 1900) % 100;
break;
}
case 'e':
tm.tm_mday = parse_number();
break;
case 'H':
tm.tm_hour = parse_number();
break;
case 'I': {
int num = parse_number();
tm.tm_hour = num % 12;
break;
}
case 'j':
// a little trickery here... we can get mktime() to figure out mon and mday using out of range values.
// yday is not used so setting it is pointless.
tm.tm_mday = parse_number();
tm.tm_mon = 0;
mktime(&tm);
break;
case 'm': {
int num = parse_number();
tm.tm_mon = num - 1;
break;
}
case 'M':
tm.tm_min = parse_number();
break;
case 'n':
case 't':
string_lexer.consume_while(is_ascii_blank);
break;
case 'r':
case 'p': {
auto ampm = string_lexer.consume(2);
if (ampm == "PM") {
if (tm.tm_hour < 12)
tm.tm_hour += 12;
} else if (ampm != "AM") {
return {};
}
break;
}
case 'R':
tm.tm_hour = parse_number();
consume(':');
tm.tm_min = parse_number();
break;
case 'S':
tm.tm_sec = parse_number();
break;
case 'T':
tm.tm_hour = parse_number();
consume(':');
tm.tm_min = parse_number();
consume(':');
tm.tm_sec = parse_number();
break;
case 'w':
tm.tm_wday = parse_number();
break;
case 'y': {
int year = parse_number();
tm.tm_year = year <= 99 && year > 69 ? 1900 + year : 2000 + year;
break;
}
case 'Y': {
int year = parse_number();
tm.tm_year = year - 1900;
break;
}
case 'z': {
tm_represents_utc_time = true;
if (string_lexer.consume_specific('Z')) {
// UTC time
break;
}
int sign;
if (string_lexer.consume_specific('+'))
sign = -1;
else if (string_lexer.consume_specific('-'))
sign = +1;
else
return {};
auto hours = parse_number();
int minutes;
if (string_lexer.consume_specific(':')) {
minutes = parse_number();
} else {
minutes = hours % 100;
hours = hours / 100;
}
tm.tm_hour += sign * hours;
tm.tm_min += sign * minutes;
break;
}
case 'x': {
tm_represents_utc_time = true;
auto hours = parse_number();
int minutes;
if (string_lexer.consume_specific(':')) {
minutes = parse_number();
} else {
minutes = hours % 100;
hours = hours / 100;
}
tm.tm_hour -= hours;
tm.tm_min -= minutes;
break;
}
case 'X': {
if (!string_lexer.consume_specific('.'))
return {};
auto discarded = parse_number();
(void)discarded; // NOTE: the tm structure does not support sub second precision, so drop this value.
break;
}
case 'Z':
parsed_time_zone = parse_time_zone_name(string_lexer);
if (!parsed_time_zone.has_value())
return {};
tm_represents_utc_time = true;
break;
case '+': {
Optional<char> next_format_character;
if (format_pos + 1 < format.length()) {
next_format_character = format[format_pos + 1];
// Disallow another formatter directly after %+. This is to avoid ambiguity when parsing a string like
// "ignoreJan" with "%+%b", as it would be non-trivial to know that where the %b field begins.
if (next_format_character == '%')
return {};
}
auto discarded = string_lexer.consume_until([&](auto ch) { return ch == next_format_character; });
if (discarded.is_empty())
return {};
break;
}
case '%':
consume('%');
break;
default:
parsing_failed = true;
break;
}
if (parsing_failed)
return {};
format_pos++;
}
if (!string_lexer.is_eof() || format_pos != format.length())
return {};
// If an explicit time zone offset was present, the time in tm was shifted to UTC. If a time zone name was present,
// the time in tm needs to be shifted to UTC. In both cases, convert the result to local time, as that is what is
// expected by `mktime`.
if (tm_represents_utc_time) {
auto utc_time = UnixDateTime::from_seconds_since_epoch(timegm(&tm));
if (parsed_time_zone.has_value())
apply_time_zone_offset(*parsed_time_zone, utc_time);
time_t utc_time_t = utc_time.seconds_since_epoch();
localtime_r(&utc_time_t, &tm);
}
return DateTime::from_timestamp(mktime(&tm));
}
}
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