cyclic_timer.h

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#pragma once
 
#include <chrono>
#include <cstdint>
 
namespace mm::core {
 
class CyclicTimer {
 public:
  explicit CyclicTimer(std::chrono::microseconds period);
 
  // Trivially destructible only in the build being analysed: the Windows implementation closes the
  // waitable-timer handle here, so defaulting this would leak a kernel object on the one platform
  // that owns one.
  // NOLINTNEXTLINE(performance-trivially-destructible)
  ~CyclicTimer();
 
  CyclicTimer(const CyclicTimer&) = delete;
  CyclicTimer& operator=(const CyclicTimer&) = delete;
 
  uint64_t waitForNextCycle();
 
  void setPeriod(std::chrono::microseconds period);
 
 private:
#ifdef _WIN32
  void* handle_ = nullptr;   // HANDLE — avoids pulling <windows.h> into every consumer
  int64_t qpcFreq_ = 0;      // QueryPerformanceCounter ticks per second
  int64_t periodTicks_ = 0;  // period expressed in QPC ticks
  int64_t next_ = 0;         // absolute deadline on the QPC (monotonic) timeline, in ticks
#else
  void advanceOnePeriod() {
    next_nsec_ += period_ns_;
    if (next_nsec_ >= 1'000'000'000L) {
      next_nsec_ -= 1'000'000'000L;
      next_sec_++;
    }
  }
 
  int64_t period_ns_ = 0;
  int64_t next_sec_ = 0;
  int64_t next_nsec_ = 0;
#endif
};
 
}  // namespace mm::core