Timestamp.h

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#ifndef canvas_Persistency_Provenance_Timestamp_h
#define canvas_Persistency_Provenance_Timestamp_h

#include <cstdint>
#include <string>

namespace art {
  using TimeValue_t = std::uint64_t;

  class Timestamp {
  public:
    constexpr Timestamp(TimeValue_t const iValue)
      : timeLow_{static_cast<std::uint32_t>(lowMask() & iValue)}
      , timeHigh_{static_cast<std::uint32_t>(iValue >> 32)}
    {}

    constexpr Timestamp()
      : timeLow_{invalidTimestamp().timeLow_}
      , timeHigh_{invalidTimestamp().timeHigh_}
    {}

    constexpr TimeValue_t
    value() const
    {
      return (static_cast<std::uint64_t>(timeHigh_) << 32) | timeLow_;
    }

    constexpr std::uint32_t
    timeLow() const
    {
      return timeLow_;
    }
    constexpr std::uint32_t
    timeHigh() const
    {
      return timeHigh_;
    }

    // ---------- const member functions ---------------------
    constexpr bool
    operator==(Timestamp const& iRHS) const
    {
      return timeHigh_ == iRHS.timeHigh_ && timeLow_ == iRHS.timeLow_;
    }

    constexpr bool
    operator!=(Timestamp const& iRHS) const
    {
      return !(*this == iRHS);
    }

    constexpr bool
    operator<(Timestamp const& iRHS) const
    {
      return timeHigh_ == iRHS.timeHigh_ ? timeLow_ < iRHS.timeLow_ :
                                           timeHigh_ < iRHS.timeHigh_;
    }

    constexpr bool
    operator<=(Timestamp const& iRHS) const
    {
      return timeHigh_ == iRHS.timeHigh_ ? timeLow_ <= iRHS.timeLow_ :
                                           timeHigh_ <= iRHS.timeHigh_;
    }

    constexpr bool
    operator>(Timestamp const& iRHS) const
    {
      return timeHigh_ == iRHS.timeHigh_ ? timeLow_ > iRHS.timeLow_ :
                                           timeHigh_ > iRHS.timeHigh_;
    }

    constexpr bool
    operator>=(Timestamp const& iRHS) const
    {
      return timeHigh_ == iRHS.timeHigh_ ? timeLow_ >= iRHS.timeLow_ :
                                           timeHigh_ >= iRHS.timeHigh_;
    }

    // ---------- static member functions --------------------
    static constexpr Timestamp
    invalidTimestamp()
    {
      return Timestamp{0};
    }
    static constexpr Timestamp
    endOfTime()
    {
      return Timestamp{-1ull};
    }
    static constexpr Timestamp
    beginOfTime()
    {
      return Timestamp{1};
    }

  private:
    std::uint32_t timeLow_;
    std::uint32_t timeHigh_;

    static constexpr TimeValue_t
    lowMask()
    {
      return 0xFFFFFFFF;
    }
  };

  // Prints out a string of the form YYYYMMDDTHHMMSS, where 'T' is the
  // delimiter between the day and the time.  Use this function if the
  // art::TimeStamp object was constructed from calling time(nullptr).
  std::string to_iso_string_assuming_unix_epoch(Timestamp const&);
}
#endif /* canvas_Persistency_Provenance_Timestamp_h */

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