BackendTscClock.h

#pragma once

#include "quill/backend/BackendManager.h"
#include "quill/core/Attributes.h"
#include "quill/core/Rdtsc.h"

#include <chrono>
#include <cstdint>

QUILL_BEGIN_NAMESPACE

QUILL_BEGIN_EXPORT

class BackendTscClock
{
public:
  class RdtscVal
  {
  public:
    RdtscVal(RdtscVal const& other) = default;
    RdtscVal(RdtscVal&& other) noexcept = default;
    RdtscVal& operator=(RdtscVal const& other) = default;
    RdtscVal& operator=(RdtscVal&& other) noexcept = default;

    QUILL_NODISCARD QUILL_ATTRIBUTE_HOT uint64_t value() const noexcept { return _value; }

  private:
    RdtscVal() noexcept : _value(detail::rdtsc()) {}
    friend BackendTscClock;

    uint64_t _value;
  };

public:
  using duration = std::chrono::nanoseconds;
  using rep = duration::rep;
  using period = duration::period;
  using time_point = std::chrono::time_point<BackendTscClock, duration>;
  static constexpr bool is_steady = false;

  QUILL_NODISCARD QUILL_ATTRIBUTE_HOT static time_point now()
  {
    uint64_t const ts = detail::BackendManager::instance().convert_rdtsc_to_epoch_time(detail::rdtsc());

    return ts ? time_point{std::chrono::nanoseconds{ts}}
              : time_point{std::chrono::nanoseconds{
                  std::chrono::time_point_cast<std::chrono::nanoseconds>(std::chrono::system_clock::now())
                    .time_since_epoch()
                    .count()}};
  }

  QUILL_NODISCARD QUILL_ATTRIBUTE_HOT static RdtscVal rdtsc() noexcept { return RdtscVal{}; }

  QUILL_NODISCARD QUILL_ATTRIBUTE_HOT static time_point to_time_point(RdtscVal rdtsc)
  {
    return time_point{std::chrono::nanoseconds{
      detail::BackendManager::instance().convert_rdtsc_to_epoch_time(rdtsc.value())}};
  }
};

QUILL_END_EXPORT

QUILL_END_NAMESPACE