DateTime.h

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// -*- lsst-c++ -*-

/*
 * LSST Data Management System
 * Copyright 2008, 2009, 2010 LSST Corporation.
 *
 * This product includes software developed by the
 * LSST Project (http://www.lsst.org/).
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the LSST License Statement and
 * the GNU General Public License along with this program.  If not,
 * see <http://www.lsstcorp.org/LegalNotices/>.
 */

#ifndef LSST_DAF_BASE_DATETIME_H
#define LSST_DAF_BASE_DATETIME_H

#include <cstdint>
#include <ctime>
#include <limits>
#include <sys/time.h>
#include <string>

#include "lsst/base.h"
#include "lsst/pex/exceptions.h"

// Forward declaration of the boost::serialization::access class.
namespace boost {
namespace serialization {
class access;
}
}  // namespace boost

namespace lsst {
namespace daf {
namespace base {

class LSST_EXPORT DateTime {
public:
    enum DateSystem { JD = 0, MJD, EPOCH };
    enum Timescale {
        TAI = 5,
        UTC,
        TT
    };  // use values that do not overlap DateSystem
        // to avoid confusing one for the other in Python
    // an invalid DateTime has _nsec == invalid_nsecs
    constexpr static long long invalid_nsecs = std::numeric_limits<std::int64_t>::min();

    explicit DateTime();

    explicit DateTime(long long nsecs, Timescale scale = TAI);

    explicit DateTime(double date, DateSystem system = MJD, Timescale scale = TAI);

    DateTime(int year, int month, int day, int hr, int min, int sec, Timescale scale = TAI);

    explicit DateTime(std::string const& iso8601, Timescale scale);

    long long nsecs(Timescale scale = TAI) const;

    double get(DateSystem system = MJD, Timescale scale = TAI) const;

    std::string toString(Timescale scale) const;

    struct tm gmtime(Timescale scale) const;

    struct timespec timespec(Timescale scale) const;

    struct timeval timeval(Timescale scale) const;

    bool isValid() const { return _nsecs != DateTime::invalid_nsecs; };

    bool operator==(DateTime const& rhs) const;

    std::size_t hash_value() const noexcept;

    static DateTime now(void);

    static void initializeLeapSeconds(std::string const& leapString);

private:
    long long _nsecs;  

    void _assertValid() const {
        if (!isValid()) {
            throw LSST_EXCEPT(pex::exceptions::RuntimeError, "DateTime not valid");
        }
    }

    double _getMjd(Timescale scale) const;

    double _getJd(Timescale scale) const;

    double _getEpoch(Timescale scale) const;

    void setNsecsFromMjd(double mjd, Timescale scale);

    void setNsecsFromJd(double jd, Timescale scale);

    void setNsecsFromEpoch(double epoch, Timescale scale);

    friend class boost::serialization::access;

    template <class Archive>
    void serialize(Archive ar, int const version) {
        ar& _nsecs;
    }
};

}  // namespace base
}  // namespace daf
}  // namespace lsst

namespace std {
template <>
struct hash<lsst::daf::base::DateTime> {
    using argument_type = lsst::daf::base::DateTime;
    using result_type = size_t;
    size_t operator()(argument_type const& obj) const noexcept { return obj.hash_value(); }
};
}  // namespace std

#endif