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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"; return "GMT";
} }
static std::string GetOsTimeZoneOffset() { // Results are not comparable to seconds since Epoch
const std::time_t t{std::time(nullptr)}; static std::time_t TmSpecToSeconds(const struct std::tm& spec) {
const std::tm tm{*std::localtime(&t)}; std::time_t cumulative = spec.tm_year;
cumulative = cumulative * 365 + spec.tm_yday; // Years to days
return fmt::format("{:%z}", tm); 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
static int ConvertOsTimeZoneOffsetToInt(const std::string& timezone) { return cumulative;
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;
}
} }
std::chrono::seconds GetCurrentOffsetSeconds() { 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 // gmt_seconds is a different offset than time(nullptr)
seconds += (offset % 100) * 60; // Convert minute component to seconds 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 // 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() { 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 seconds = static_cast<s64>(GetCurrentOffsetSeconds().count());
const s64 minutes = seconds / 60; const s64 minutes = seconds / 60;
@ -97,7 +87,6 @@ std::string FindSystemTimeZone() {
} }
} }
return fmt::format("Etc/GMT{:s}{:d}", hours > 0 ? "-" : "+", std::abs(hours)); return fmt::format("Etc/GMT{:s}{:d}", hours > 0 ? "-" : "+", std::abs(hours));
#endif
} }
} // namespace Common::TimeZone } // namespace Common::TimeZone