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common: Move system time zone string detection

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Moves it from Settings to Common::TimeZone, since this algorithm doesn't
depend on the setting. It also lets us use it in other libraries.

common: Various fixes

time_zone: Don't double up the std::abs

Too many absolute values were causing mirrored time zones to resolve
as the same.
This commit is contained in:
lat9nq 2023-05-23 18:32:28 -04:00
parent 011438fa95
commit 3979c7daa4
3 changed files with 84 additions and 76 deletions
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79
src/common/settings.cpp
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@ -3,18 +3,14 @@
#if __cpp_lib_chrono >= 201907L
#include <chrono>
#else
#include <ctime>
#include <limits>
#endif
#include <string_view>
#include <fmt/chrono.h>
#include <fmt/core.h>
#include "common/assert.h"
#include "common/fs/path_util.h"
#include "common/logging/log.h"
#include "common/settings.h"
#include "common/time_zone.h"
namespace Settings {
@ -22,83 +18,22 @@ Values values;
static bool configuring_global = true;
std::string GetTimeZoneString() {
static constexpr std::array timezones{
"GMT", "GMT", "CET", "CST6CDT", "Cuba", "EET", "Egypt", "Eire",
"EST", "EST5EDT", "GB", "GB-Eire", "GMT", "GMT+0", "GMT-0", "GMT0",
"Greenwich", "Hongkong", "HST", "Iceland", "Iran", "Israel", "Jamaica", "Japan",
"Kwajalein", "Libya", "MET", "MST", "MST7MDT", "Navajo", "NZ", "NZ-CHAT",
"Poland", "Portugal", "PRC", "PST8PDT", "ROC", "ROK", "Singapore", "Turkey",
"UCT", "Universal", "UTC", "W-SU", "WET", "Zulu",
};
const auto time_zone_index = static_cast<std::size_t>(values.time_zone_index.GetValue());
ASSERT(time_zone_index < timezones.size());
ASSERT(time_zone_index < Common::TimeZone::GetTimeZoneStrings().size());
std::string location_name;
switch (time_zone_index) {
case 0: { // Auto
if (time_zone_index == 0) { // Auto
#if __cpp_lib_chrono >= 201907L
const struct std::chrono::tzdb& time_zone_data = std::chrono::get_tzdb();
const std::chrono::time_zone* current_zone = time_zone_data.current_zone();
std::string_view current_zone_name = current_zone->name();
location_name = current_zone_name;
#elif 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"
location_name = timezones[0];
break;
#else
static constexpr std::array offsets{
0, 0, 3600, -21600, -19768, 7200, 7509, -1521, -18000, -18000,
-75, -75, 0, 0, 0, 0, 0, 27402, -36000, -968,
12344, 8454, -18430, 33539, 40160, 3164, 3600, -25200, -25200, -25196,
41944, 44028, 5040, -2205, 29143, -28800, 29160, 30472, 24925, 6952,
0, 0, 0, 9017, 0, 0,
};
static constexpr std::array dst{
false, false, true, true, true, true, true, true, false, true, true, true,
false, false, false, false, false, true, false, false, true, true, true, true,
false, true, true, false, true, true, true, true, true, true, true, true,
true, true, true, true, false, false, false, true, true, false,
};
const auto now = std::time(nullptr);
const struct std::tm& local = *std::localtime(&now);
const std::string clock_offset_s = fmt::format("{:%z}", local);
if (clock_offset_s.empty()) {
location_name = timezones[0];
break;
}
const int hours_offset = std::stoi(clock_offset_s) / 100;
const int minutes_offset = std::stoi(clock_offset_s) - hours_offset * 100;
const int system_offset =
hours_offset * 3600 + minutes_offset * 60 - (local.tm_isdst ? 3600 : 0);
int min = std::numeric_limits<int>::max();
int min_index = -1;
for (u32 i = 2; i < offsets.size(); i++) {
// Skip if system is celebrating DST but considered time zone does not
if (local.tm_isdst && !dst[i]) {
continue;
}
const auto offset = offsets[i];
const int difference = std::abs(std::abs(offset) - std::abs(system_offset));
if (difference < min) {
min = difference;
min_index = i;
}
}
location_name = timezones[min_index];
location_name = Common::TimeZone::FindSystemTimeZone();
#endif
break;
} else {
location_name = Common::TimeZone::GetTimeZoneStrings()[time_zone_index];
}
default:
location_name = timezones[time_zone_index];
break;
}
return location_name;
}