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serenity/Userland/Libraries/LibCore/DateTime.cpp
Timothy Flynn 350fdf1e43 LibCore+LibTimeZone: Support time zone names in Core::DateTime::parse 
LibCore currently cannot depend on LibTimeZone directly. All build-time
code generators depend on LibCore, so there'd be a circular dependency:
LibCore -> LibTimeZone -> GenerateTZData -> LibCore.

So to support parsing time zone names and applying their offsets, add a
couple of weakly-defined helper functions. These work similar to the way
AK::String declares some methods that LibUnicode defines. Any user who
wants to parse time zone names (from outside of LibCore itself) can link
against LibTimeZone to receive full support.
2023-11-08 09:28:17 +01:00

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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 <LibTimeZone/DateTime.h>
#include <errno.h>
#include <time.h>
namespace Core {
Optional<StringView> __attribute__((weak)) parse_time_zone_name(GenericLexer&) { return {}; }
void __attribute__((weak)) apply_time_zone_offset(StringView, UnixDateTime&) { }
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;
}
ErrorOr<String> DateTime::to_string(StringView format) const
{
struct tm tm;
localtime_r(&m_timestamp, &tm);
StringBuilder builder;
int 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 (int 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();
}
DeprecatedString DateTime::to_deprecated_string(StringView format) const
{
return MUST(to_string(format)).to_deprecated_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 'Z':
parsed_time_zone = parse_time_zone_name(string_lexer);
if (!parsed_time_zone.has_value())
return {};
tm_represents_utc_time = true;
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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