Common/Timer: Add a SteadyAwakeClock class which counts non-suspended system running time.

1 files changed, 34 insertions, 0 deletions

diff --git a/Source/Core/Common/Timer.cpp b/Source/Core/Common/Timer.cpp
index 0a23080c6f..0e260b833c 100644
--- a/Source/Core/Common/Timer.cpp
+++ b/Source/Core/Common/Timer.cpp
@@ -5,6 +5,7 @@
 
 #include <chrono>
 #include <thread>
+#include "Common/CommonFuncs.h"
 
 #ifdef _WIN32
 #include <Windows.h>
@@ -194,4 +195,37 @@ void PrecisionTimer::SleepUntil(Clock::time_point target)
   }
 }
 
+// Results are appropriately slewed on Linux, but not on Windows, macOS, or FreeBSD.
+// Clocks with that functionality seem to not be available there.
+auto SteadyAwakeClock::now() -> time_point
+{
+#if defined(_WIN32)
+  // The count is system time "in units of 100 nanoseconds".
+  using InterruptDuration = std::chrono::duration<ULONGLONG, std::ratio<100, std::nano::den>::type>;
+
+  ULONGLONG interrupt_time{};
+  if (!QueryUnbiasedInterruptTime(&interrupt_time))
+    ERROR_LOG_FMT(COMMON, "QueryUnbiasedInterruptTime");
+
+  return time_point{InterruptDuration{interrupt_time}};
+#else
+  // Note that Linux's CLOCK_MONOTONIC "does not count time that the system is suspended".
+  // This is in contrast to the behavior on macOS and FreeBSD.
+  static constexpr auto clock_id =
+#if defined(__linux__)
+      CLOCK_MONOTONIC;
+#elif defined(__APPLE__)
+      CLOCK_UPTIME_RAW;
+#else
+      CLOCK_UPTIME;
+#endif
+
+  timespec ts{};
+  if (clock_gettime(clock_id, &ts) != 0)
+    ERROR_LOG_FMT(COMMON, "clock_gettime: {}", LastStrerrorString());
+
+  return time_point{std::chrono::seconds{ts.tv_sec} + std::chrono::nanoseconds{ts.tv_nsec}};
+#endif
+}
+
 }  // Namespace Common