1 files changed, 96 insertions, 0 deletions

diff --git a/timer/src/timer.c b/timer/src/timer.c
new file mode 100644
index 0000000..2ee8ef5
--- /dev/null
+++ b/timer/src/timer.c
@@ -0,0 +1,96 @@
+#include "timer.h"
+
+#include <stdlib.h>
+
+#ifdef _WIN32
+static const int64_t microseconds = 1000000;
+#endif
+static const int64_t nanoseconds = 1000000000;
+
+#ifdef _WIN32
+#define WIN32_LEAN_AND_MEAN
+#include <Windows.h>
+#endif
+
+#ifdef _WIN32
+static double seconds_per_count;
+#endif
+
+static void timer_initialise() {
+#ifdef _WIN32
+  __int64 counts_per_sec;
+  QueryPerformanceFrequency((LARGE_INTEGER*)&counts_per_sec);
+  seconds_per_count = 1.0 / (double)counts_per_sec;
+#endif
+}
+
+Timer timer_make(void) {
+  timer_initialise();
+  Timer timer = {0};
+  timer_start(&timer);
+  return timer;
+}
+
+void timer_start(Timer* timer) {
+  timer->start_time = time_now();
+  timer->last_tick = timer->start_time;
+  timer->running_time = 0;
+  timer->delta_time = 0;
+}
+
+void timer_tick(Timer* timer) {
+  const time_point this_tick = time_now();
+  timer->running_time = time_diff(timer->start_time, this_tick);
+  timer->delta_time = time_diff(timer->last_tick, this_tick);
+  timer->last_tick = this_tick;
+}
+
+time_point time_now(void) {
+  time_point t;
+#ifdef _WIN32
+  QueryPerformanceCounter((LARGE_INTEGER*)&t);
+#else
+  clock_gettime(CLOCK_REALTIME, &t);
+#endif
+  return t;
+}
+
+time_delta time_diff(time_point start, time_point end) {
+#ifdef _WIN32
+  // Force nonnegative. The DXSDK's CDXUTTimer mentions that if the
+  // processor goes into a power save mode or we get shuffled to
+  // another processor, then the delta time can be negative.
+  return std::max(0, end - start);
+#else
+  return (end.tv_sec - start.tv_sec) * 1e9 + (end.tv_nsec - start.tv_nsec);
+#endif
+}
+
+double time_delta_to_sec(time_delta dt) {
+#ifdef _WIN32
+  return (double)dt * seconds_per_count;
+#else
+  return (double)dt * 1.0e-9;
+#endif
+}
+
+time_delta sec_to_time_delta(double seconds) {
+#ifdef _WIN32
+  return (time_delta)(seconds / seconds_per_count);
+#else
+  return (time_delta)(seconds * 1.0e9);
+#endif
+}
+
+void time_sleep(time_delta dt) {
+#ifdef _WIN32
+  const int64_t ms = dt / microseconds;
+  Sleep((DWORD)(ms));
+#else
+  const int64_t sec = dt / nanoseconds;
+  struct timespec ts;
+  ts.tv_sec = (long)sec;
+  ts.tv_nsec = (long)(dt % nanoseconds);
+  nanosleep(&ts, NULL);
+#endif
+}