ardupilot/libraries/AP_RTC/AP_RTC.h

#pragma once

#include <AP_Param/AP_Param.h>

#include <stdint.h>
#include <time.h>
class AP_RTC {

public:

    AP_RTC();

    static const struct AP_Param::GroupInfo var_info[];

    AP_Int8 allowed_types;
    AP_Int16 tz_min;

    // ordering is important in source_type; lower-numbered is
    // considered a better time source.  These values are documented
    // and used in the parameters!
    enum source_type : uint8_t {
        SOURCE_GPS = 0,
        SOURCE_MAVLINK_SYSTEM_TIME = 1,
        SOURCE_HW = 2,
        SOURCE_NONE,
    };

    /*
      get clock in UTC microseconds.  Returns false if it is not available.
     */
    bool get_utc_usec(uint64_t &usec) const;

    // set the system time.  If the time has already been set by
    // something better (according to source_type), this set will be
    // ignored.
    void set_utc_usec(uint64_t time_utc_usec, source_type type);

    /*
      get time in UTC hours, minutes, seconds and milliseconds
     */
    bool get_system_clock_utc(uint8_t &hour, uint8_t &min, uint8_t &sec, uint16_t &ms) const;
    
    bool get_local_time(uint8_t &hour, uint8_t &min, uint8_t &sec, uint16_t &ms) const;

    uint32_t get_time_utc(int32_t hour, int32_t min, int32_t sec, int32_t ms);

    // replacement for mktime()
    static time_t mktime(const struct tm *t);

    // get singleton instance
    static AP_RTC *get_singleton() {
        return _singleton;
    }

    // allow threads to lock against RTC update
    HAL_Semaphore &get_semaphore(void) {
        return rsem;
    }
    
private:

    static AP_RTC *_singleton;
    HAL_Semaphore_Recursive rsem;

    source_type rtc_source_type = SOURCE_NONE;
    int64_t rtc_shift;

};

namespace AP {
    AP_RTC &rtc();
};