core: don't use double in monotonic clock

Chilledheart · Sep 14, 2024 · 7b1f02a · 7b1f02a
1 parent 1eb7ebc
commit 7b1f02a
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Showing 3 changed files with 23 additions and 5 deletions.
diff --git a/src/core/utils_freebsd.cpp b/src/core/utils_freebsd.cpp
@@ -43,7 +43,9 @@ uint64_t GetMonotonicTime() {
     PLOG(WARNING) << "clock_gettime failed";
     return 0;
   }
-  return static_cast<double>(ts.tv_sec - start_ts.tv_sec) * NS_PER_SECOND + ts.tv_nsec - start_ts.tv_nsec;
+  ts.tv_sec -= start_ts.tv_sec;
+  ts.tv_nsec -= start_ts.tv_nsec;
+  return static_cast<uint64_t>(ts.tv_sec) * NS_PER_SECOND + ts.tv_nsec;
 }
 
 #endif  // BUILDFLAG(IS_FREEBSD)
diff --git a/src/core/utils_linux.cpp b/src/core/utils_linux.cpp
@@ -178,7 +178,9 @@ uint64_t GetMonotonicTime() {
     PLOG(WARNING) << "clock_gettime failed";
     return 0;
   }
-  return static_cast<double>(ts.tv_sec - start_ts.tv_sec) * NS_PER_SECOND + ts.tv_nsec - start_ts.tv_nsec;
+  ts.tv_sec -= start_ts.tv_sec;
+  ts.tv_nsec -= start_ts.tv_nsec;
+  return static_cast<uint64_t>(ts.tv_sec) * NS_PER_SECOND + ts.tv_nsec;
 }
 
 #endif  // __linux__
diff --git a/src/core/utils_win.cpp b/src/core/utils_win.cpp
@@ -164,7 +164,7 @@ bool SetCurrentThreadName(const std::string& name) {
   return SUCCEEDED(ret);
 }
 
-uint64_t GetMonotonicTime() {
+static uint64_t GetMonotonicTimeQPC() {
   static LARGE_INTEGER StartTime, Frequency;
   static bool started;
 
@@ -197,12 +197,26 @@ uint64_t GetMonotonicTime() {
   // to microseconds *before* dividing by ticks-per-second.
   //
 
-  ElapsedNanoseconds.QuadPart =
-      static_cast<double>(ElapsedNanoseconds.QuadPart) * NS_PER_SECOND / static_cast<double>(Frequency.QuadPart);
+  ElapsedNanoseconds.QuadPart *= NS_PER_SECOND;
+  ElapsedNanoseconds.QuadPart /= Frequency.QuadPart;
 
   return ElapsedNanoseconds.QuadPart;
 }
 
+uint64_t GetMonotonicTime() {
+#if _WIN32_WINNT >= 0x0600
+  return GetMonotonicTimeQPC();
+#else
+  /* if vista or later */
+  static const auto fPointer =
+      reinterpret_cast<void*>(::GetProcAddress(::GetModuleHandleW(L"Kernel32.dll"), "GetTickCount64"));
+  if (fPointer) {
+    return GetMonotonicTimeQPC();
+  }
+  return GetTickCount() * 1000000;
+#endif
+}
+
 static bool IsHandleConsole(HANDLE handle) {
   DWORD mode;
   return handle != HANDLE() && handle != INVALID_HANDLE_VALUE &&