common: Add module to get the current time zone.

src/common/CMakeLists.txt

@@ -148,6 +148,8 @@ add_library(common STATIC
     thread.h
     thread_queue_list.h
     threadsafe_queue.h
+    time_zone.cpp
+    time_zone.h
     timer.cpp
     timer.h
     uint128.cpp

src/common/time_zone.cpp

@@ -0,0 +1,49 @@
+// Copyright 2020 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <chrono>
+#include <iomanip>
+#include <sstream>
+
+#include "common/logging/log.h"
+#include "common/time_zone.h"
+
+namespace Common::TimeZone {
+
+std::string GetDefaultTimeZone() {
+    return "GMT";
+}
+
+static std::string GetOsTimeZoneOffset() {
+    const std::time_t t{std::time(nullptr)};
+    const std::tm tm{*std::localtime(&t)};
+
+    std::stringstream ss;
+    ss << std::put_time(&tm, "%z"); // Get the current timezone offset, e.g. "-400", as a string
+
+    return ss.str();
+}
+
+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;
+    }
+}
+
+int GetCurrentOffsetSeconds() {
+    const int offset{ConvertOsTimeZoneOffsetToInt(GetOsTimeZoneOffset())};
+
+    int seconds{(offset / 100) * 60 * 60}; // Convert hour component to seconds
+    seconds += (offset % 100) * 60;        // Convert minute component to seconds
+
+    return seconds;
+}
+
+} // namespace Common::TimeZone

src/common/time_zone.h

@@ -0,0 +1,17 @@
+// Copyright 2020 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <string>
+
+namespace Common::TimeZone {
+
+/// Gets the default timezone, i.e. "GMT"
+std::string GetDefaultTimeZone();
+
+/// Gets the offset of the current timezone (from the default), in seconds
+int GetCurrentOffsetSeconds();
+
+} // namespace Common::TimeZone