diff options
Diffstat (limited to 'platform/windows/os_windows.cpp')
| -rw-r--r-- | platform/windows/os_windows.cpp | 21 |
1 files changed, 19 insertions, 2 deletions
diff --git a/platform/windows/os_windows.cpp b/platform/windows/os_windows.cpp index f78c87be93..c32e50e472 100644 --- a/platform/windows/os_windows.cpp +++ b/platform/windows/os_windows.cpp @@ -418,12 +418,29 @@ void OS_Windows::delay_usec(uint32_t p_usec) const { uint64_t OS_Windows::get_ticks_usec() const { uint64_t ticks; - uint64_t time; + // This is the number of clock ticks since start if (!QueryPerformanceCounter((LARGE_INTEGER *)&ticks)) ticks = (UINT64)timeGetTime(); + // Divide by frequency to get the time in seconds - time = ticks * 1000000L / ticks_per_second; + // original calculation shown below is subject to overflow + // with high ticks_per_second and a number of days since the last reboot. + // time = ticks * 1000000L / ticks_per_second; + + // we can prevent this by either using 128 bit math + // or separating into a calculation for seconds, and the fraction + uint64_t seconds = ticks / ticks_per_second; + + // compiler will optimize these two into one divide + uint64_t leftover = ticks % ticks_per_second; + + // remainder + uint64_t time = (leftover * 1000000L) / ticks_per_second; + + // seconds + time += seconds * 1000000L; + // Subtract the time at game start to get // the time since the game started time -= ticks_start; |