sokol_tim.h: apply the same 64-bit overflow protection on OSX as for Windows

1 files changed, 15 insertions, 13 deletions

diff --git a/sokol_time.h b/sokol_time.h
index 357ba57b..ee207a27 100644
--- a/sokol_time.h
+++ b/sokol_time.h
@@ -117,6 +117,18 @@ static uint64_t _stm_osx_start;
 static uint64_t _stm_posix_start;
 #endif
 
+/* prevent 64-bit overflow when computing relative timestamp
+    see https://gist.github.com/jspohr/3dc4f00033d79ec5bdaf67bc46c813e3
+*/
+#if defined(_WIN32) || (defined(__APPLE__) && defined(__MACH__))
+static int64_t int64_muldiv(int64_t value, int64_t numer, int64_t denom) {
+    int64_t q = value / denom;
+    int64_t r = value % denom;
+    return q * numer + r * numer / denom;
+}
+#endif
+
+
 void stm_setup(void) {
     SOKOL_ASSERT(0 == _stm_initialized);
     _stm_initialized = 1;
@@ -125,7 +137,7 @@ void stm_setup(void) {
         QueryPerformanceCounter(&_stm_win_start);
     #elif defined(__APPLE__) && defined(__MACH__)
         mach_timebase_info(&_stm_osx_timebase);
-        _stm_osx_start = (mach_absolute_time()*_stm_osx_timebase.numer)/_stm_osx_timebase.denom;
+        _stm_osx_start = mach_absolute_time();
     #else
         struct timespec ts;
         clock_gettime(CLOCK_MONOTONIC, &ts);
@@ -133,17 +145,6 @@ void stm_setup(void) {
     #endif
 }
 
-/* prevent 64-bit overflow with QPC/QPF
-    see https://gist.github.com/jspohr/3dc4f00033d79ec5bdaf67bc46c813e3
-*/
-#if defined(_WIN32)
-static int64_t int64_muldiv(int64_t value, int64_t numer, int64_t denom) {
-    int64_t q = value / denom;
-    int64_t r = value % denom;
-    return q * numer + r * numer / denom;
-}
-#endif
-
 uint64_t stm_now(void) {
     SOKOL_ASSERT(_stm_initialized);
     uint64_t now;
@@ -152,7 +153,8 @@ uint64_t stm_now(void) {
         QueryPerformanceCounter(&qpc_t);
         now = int64_muldiv(qpc_t.QuadPart - _stm_win_start.QuadPart, 1000000000, _stm_win_freq.QuadPart);
     #elif defined(__APPLE__) && defined(__MACH__)
-        now = ((mach_absolute_time()*_stm_osx_timebase.numer)/_stm_osx_timebase.denom) - _stm_osx_start;
+        const uint64_t mach_now = mach_absolute_time() - _stm_osx_start;
+        now = int64_muldiv(mach_now, _stm_osx_timebase.numer, _stm_osx_timebase.denom);
     #else
         struct timespec ts;
         clock_gettime(CLOCK_MONOTONIC, &ts);