primer commit

source/utils/delta_timer.cpp

@@ -0,0 +1,38 @@
+#include "utils/delta_timer.hpp"
+
+DeltaTimer::DeltaTimer() noexcept
+    : last_counter_(SDL_GetPerformanceCounter()),
+      perf_freq_(static_cast<double>(SDL_GetPerformanceFrequency())),
+      time_scale_(1.0F) {
+}
+
+auto DeltaTimer::tick() noexcept -> float {
+    const Uint64 NOW = SDL_GetPerformanceCounter();
+    const Uint64 DIFF = (NOW > last_counter_) ? (NOW - last_counter_) : 0;
+    last_counter_ = NOW;
+    const double SECONDS = static_cast<double>(DIFF) / perf_freq_;
+    return static_cast<float>(SECONDS * static_cast<double>(time_scale_));
+}
+
+auto DeltaTimer::peek() const noexcept -> float {
+    const Uint64 NOW = SDL_GetPerformanceCounter();
+    const Uint64 DIFF = (NOW > last_counter_) ? (NOW - last_counter_) : 0;
+    const double SECONDS = static_cast<double>(DIFF) / perf_freq_;
+    return static_cast<float>(SECONDS * static_cast<double>(time_scale_));
+}
+
+void DeltaTimer::reset(Uint64 counter) noexcept {
+    if (counter == 0) {
+        last_counter_ = SDL_GetPerformanceCounter();
+    } else {
+        last_counter_ = counter;
+    }
+}
+
+void DeltaTimer::setTimeScale(float scale) noexcept {
+    time_scale_ = std::max(scale, 0.0F);
+}
+
+auto DeltaTimer::getTimeScale() const noexcept -> float {
+    return time_scale_;
+}