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time_zone: Remove string ops for determing zone

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MinGW's strftime implementation does not work and cannot be used to
determine the time zone. Besides that, the string operations are
actually unnecessary since we can get the offset from
std::localtime.

Compare localtime to gmtime to find the zone offset on all platforms.
This commit is contained in:
lat9nq 2023-07-10 17:51:34 -04:00
parent e32ce6cc69
commit 90d76333da
1 changed files with 16 additions and 27 deletions
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43
src/common/time_zone.cpp
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@ -33,32 +33,27 @@ std::string GetDefaultTimeZone() {
return "GMT";
}
static std::string GetOsTimeZoneOffset() {
const std::time_t t{std::time(nullptr)};
const std::tm tm{*std::localtime(&t)};
return fmt::format("{:%z}", tm);
}
static int ConvertOsTimeZoneOffsetToInt(const std::string& timezone) {
try {
return std::stoi(timezone);
} catch (const std::invalid_argument&) {
LOG_CRITICAL(Common, "invalid_argument with {}!", timezone);
return 0;
} catch (const std::out_of_range&) {
LOG_CRITICAL(Common, "out_of_range with {}!", timezone);
return 0;
}
// Results are not comparable to seconds since Epoch
static std::time_t TmSpecToSeconds(const struct std::tm& spec) {
std::time_t cumulative = spec.tm_year;
cumulative = cumulative * 365 + spec.tm_yday; // Years to days
cumulative = cumulative * 24 + spec.tm_hour; // Days to hours
cumulative = cumulative * 60 + spec.tm_min; // Hours to minutes
cumulative = cumulative * 60 + spec.tm_sec; // Minutes to seconds
return cumulative;
}
std::chrono::seconds GetCurrentOffsetSeconds() {
const int offset{ConvertOsTimeZoneOffsetToInt(GetOsTimeZoneOffset())};
const std::time_t t{std::time(nullptr)};
const std::tm local{*std::localtime(&t)};
const std::tm gmt{*std::gmtime(&t)};
int seconds{(offset / 100) * 60 * 60}; // Convert hour component to seconds
seconds += (offset % 100) * 60; // Convert minute component to seconds
// gmt_seconds is a different offset than time(nullptr)
const auto gmt_seconds = TmSpecToSeconds(gmt);
const auto local_seconds = TmSpecToSeconds(local);
const auto seconds_offset = gmt_seconds - local_seconds;
return std::chrono::seconds{seconds};
return std::chrono::seconds{seconds_offset};
}
// Key is [Hours * 100 + Minutes], multiplied by 100 if DST
@ -71,11 +66,6 @@ const static std::map<s64, const char*> off_timezones = {
};
std::string FindSystemTimeZone() {
#if defined(MINGW)
// MinGW has broken strftime -- https://sourceforge.net/p/mingw-w64/bugs/793/
// e.g. fmt::format("{:%z}") -- returns "Eastern Daylight Time" when it should be "-0400"
return timezones[0];
#else
const s64 seconds = static_cast<s64>(GetCurrentOffsetSeconds().count());
const s64 minutes = seconds / 60;
@ -97,7 +87,6 @@ std::string FindSystemTimeZone() {
}
}
return fmt::format("Etc/GMT{:s}{:d}", hours > 0 ? "-" : "+", std::abs(hours));
#endif
}
} // namespace Common::TimeZone