[Kernel] Overhaul Rtl time functions.

- Add date third party submodule.
- [Kernel] Add xclock.
- [Kernel] Reimplement RtlTimeToTimeFields using std::chrono/date/xclock.
- [Kernel] Reimplement RtlTimeFieldsToTime using std::chrono/date/xclock.
- Supersedes #1612.

4 files changed, 117 insertions, 33 deletions

diff --git a/.gitmodules b/.gitmodules
index 597affeb8..b8f139b8a 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -70,3 +70,6 @@
 [submodule "third_party/premake-androidmk"]
 	path = third_party/premake-androidmk
 	url = https://github.com/Triang3l/premake-androidmk.git
+[submodule "third_party/date"]
+	path = third_party/date
+	url = https://github.com/HowardHinnant/date.git
diff --git a/src/xenia/kernel/xboxkrnl/xboxkrnl_rtl.cc b/src/xenia/kernel/xboxkrnl/xboxkrnl_rtl.cc
index e06daba48..db3cef5db 100644
--- a/src/xenia/kernel/xboxkrnl/xboxkrnl_rtl.cc
+++ b/src/xenia/kernel/xboxkrnl/xboxkrnl_rtl.cc
@@ -21,14 +21,10 @@
 #include "xenia/kernel/util/shim_utils.h"
 #include "xenia/kernel/xboxkrnl/xboxkrnl_private.h"
 #include "xenia/kernel/xboxkrnl/xboxkrnl_threading.h"
+#include "xenia/kernel/xclock.h"
 #include "xenia/kernel/xevent.h"
 #include "xenia/kernel/xthread.h"
 
-#if XE_PLATFORM_WIN32
-#include "xenia/base/platform_win.h"
-#define timegm _mkgmtime
-#endif
-
 namespace xe {
 namespace kernel {
 namespace xboxkrnl {
@@ -507,44 +503,51 @@ struct X_TIME_FIELDS {
   xe::be<uint16_t> milliseconds;
   xe::be<uint16_t> weekday;
 };
-static_assert(sizeof(X_TIME_FIELDS) == 16, "Must be LARGEINTEGER");
+static_assert_size(X_TIME_FIELDS, 16);
 
-// https://support.microsoft.com/en-us/kb/167296
+// https://docs.microsoft.com/en-us/windows-hardware/drivers/ddi/wdm/nf-wdm-rtltimetotimefields
 void RtlTimeToTimeFields(lpqword_t time_ptr,
                          pointer_t<X_TIME_FIELDS> time_fields_ptr) {
-  int64_t time_ms = time_ptr.value() / 10000 - 11644473600000LL;
-  time_t timet = time_ms / 1000;
-  struct tm* tm = gmtime(&timet);
-
-  time_fields_ptr->year = tm->tm_year + 1900;
-  time_fields_ptr->month = tm->tm_mon + 1;
-  time_fields_ptr->day = tm->tm_mday;
-  time_fields_ptr->hour = tm->tm_hour;
-  time_fields_ptr->minute = tm->tm_min;
-  time_fields_ptr->second = tm->tm_sec;
-  time_fields_ptr->milliseconds = time_ms % 1000;
-  time_fields_ptr->weekday = tm->tm_wday;
+  auto tp = XClock::to_sys(XClock::from_file_time(time_ptr.value()));
+  auto dp = date::floor<date::days>(tp);
+  auto year_month_day = date::year_month_day{dp};
+  auto weekday = date::weekday{dp};
+  auto time = date::hh_mm_ss{date::floor<std::chrono::milliseconds>(tp - dp)};
+  time_fields_ptr->year = static_cast<int>(year_month_day.year());
+  time_fields_ptr->month = static_cast<unsigned>(year_month_day.month());
+  time_fields_ptr->day = static_cast<unsigned>(year_month_day.day());
+  time_fields_ptr->weekday = weekday.c_encoding();
+  time_fields_ptr->hour = time.hours().count();
+  time_fields_ptr->minute = time.minutes().count();
+  time_fields_ptr->second = static_cast<uint16_t>(time.seconds().count());
+  time_fields_ptr->milliseconds =
+      static_cast<uint16_t>(time.subseconds().count());
 }
 DECLARE_XBOXKRNL_EXPORT1(RtlTimeToTimeFields, kNone, kImplemented);
 
+// https://docs.microsoft.com/en-us/windows-hardware/drivers/ddi/wdm/nf-wdm-rtltimefieldstotime
 dword_result_t RtlTimeFieldsToTime(pointer_t<X_TIME_FIELDS> time_fields_ptr,
                                    lpqword_t time_ptr) {
-  struct tm tm;
-  tm.tm_year = time_fields_ptr->year - 1900;
-  tm.tm_mon = time_fields_ptr->month - 1;
-  tm.tm_mday = time_fields_ptr->day;
-  tm.tm_hour = time_fields_ptr->hour;
-  tm.tm_min = time_fields_ptr->minute;
-  tm.tm_sec = time_fields_ptr->second;
-  tm.tm_isdst = 0;
-  time_t timet = timegm(&tm);
-  if (timet == -1) {
-    // set last error = ERROR_INVALID_PARAMETER
+  if (time_fields_ptr->year < 1601 || time_fields_ptr->month < 1 ||
+      time_fields_ptr->month > 11 || time_fields_ptr->day < 1 ||
+      time_fields_ptr->hour > 23 || time_fields_ptr->minute > 59 ||
+      time_fields_ptr->second > 59 || time_fields_ptr->milliseconds > 999) {
+    return 0;
+  }
+  auto year = date::year{time_fields_ptr->year};
+  auto month = date::month{time_fields_ptr->month};
+  auto day = date::day{time_fields_ptr->day};
+  auto year_month_day = date::year_month_day{year, month, day};
+  if (!year_month_day.ok()) {
     return 0;
   }
-  uint64_t time =
-      ((timet + 11644473600LL) * 1000 + time_fields_ptr->milliseconds) * 10000;
-  *time_ptr = time;
+  auto dp = static_cast<date::sys_days>(year_month_day);
+  std::chrono::system_clock::time_point time = dp;
+  time += std::chrono::hours{time_fields_ptr->hour};
+  time += std::chrono::minutes{time_fields_ptr->minute};
+  time += std::chrono::seconds{time_fields_ptr->second};
+  time += std::chrono::milliseconds{time_fields_ptr->milliseconds};
+  *time_ptr = XClock::to_file_time(XClock::from_sys(time));
   return 1;
 }
 DECLARE_XBOXKRNL_EXPORT1(RtlTimeFieldsToTime, kNone, kImplemented);
diff --git a/src/xenia/kernel/xclock.h b/src/xenia/kernel/xclock.h
new file mode 100644
index 000000000..809dfd775
--- /dev/null
+++ b/src/xenia/kernel/xclock.h
@@ -0,0 +1,78 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2020 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_KERNEL_XCLOCK_H_
+#define XENIA_KERNEL_XCLOCK_H_
+
+#include <chrono>
+
+#include "xenia/base/clock.h"
+
+#include "third_party/date/include/date/date.h"
+
+namespace xe {
+namespace kernel {
+
+struct XClock {
+  using rep = int64_t;
+  using period = std::ratio_multiply<std::ratio<100>, std::nano>;
+  using duration = std::chrono::duration<rep, period>;
+  using time_point = std::chrono::time_point<XClock>;
+  static constexpr bool is_steady = false;
+
+  static time_point now() noexcept {
+    return from_file_time(Clock::QueryGuestSystemTime());
+  }
+
+  static uint64_t to_file_time(time_point const& tp) noexcept {
+    return static_cast<uint64_t>(tp.time_since_epoch().count());
+  }
+
+  static time_point from_file_time(uint64_t const& tp) noexcept {
+    return time_point{duration{tp}};
+  }
+
+  static std::chrono::system_clock::time_point to_sys(time_point const& tp) {
+    // TODO(gibbed): verify behavior under Linux
+    using sys_duration = std::chrono::system_clock::duration;
+    using sys_time = std::chrono::system_clock::time_point;
+    auto dp = tp;
+    dp += system_clock_delta();
+    auto cdp = std::chrono::time_point_cast<sys_duration>(dp);
+    return sys_time{cdp.time_since_epoch()};
+  }
+
+  static time_point from_sys(std::chrono::system_clock::time_point const& tp) {
+    // TODO(gibbed): verify behavior under Linux
+    auto ctp = std::chrono::time_point_cast<duration>(tp);
+    auto dp = time_point{ctp.time_since_epoch()};
+    dp -= system_clock_delta();
+    return dp;
+  }
+
+ private:
+  // The delta between std::chrono::system_clock (Jan 1 1970) and Xenon file
+  // time (Jan 1 1601), in seconds. In the spec std::chrono::system_clock's
+  // epoch is undefined, but C++20 cements it as Jan 1 1970.
+  static constexpr std::chrono::seconds system_clock_delta() {
+    auto filetime_epoch = date::year{1601} / date::month{1} / date::day{1};
+    auto system_clock_epoch = date::year{1970} / date::month{1} / date::day{1};
+    std::chrono::system_clock::time_point fp{
+        static_cast<date::sys_days>(filetime_epoch)};
+    std::chrono::system_clock::time_point sp{
+        static_cast<date::sys_days>(system_clock_epoch)};
+    return std::chrono::floor<std::chrono::seconds>(fp.time_since_epoch() -
+                                                    sp.time_since_epoch());
+  }
+};
+
+}  // namespace kernel
+}  // namespace xe
+
+#endif  // XENIA_KERNEL_XCLOCK_H_
diff --git a/third_party/date b/third_party/date
new file mode 160000
+Subproject 97246a638a6d8f0269f4555c5e31106a86e3fd9