RTC授时时间戳转换工具

在调试蓝牙MCU时间戳功能时，很多主流的UNIX时间戳计算工具就失效了，因为server端需要下发小端的HEX转换结果，因此我写了这个鸡肋工具来辅助调试：

#include <stdint.h>
#include <stdio.h>
#include <stdbool.h>
#include <time.h>

static bool is_leap_year(uint16_t year)
{
    return ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0));
}

static uint8_t days_in_month(uint16_t year, uint8_t month)
{
    static const uint8_t days[] = {
        31, 28, 31, 30, 31, 30,
        31, 31, 30, 31, 30, 31
    };

    if (month < 1 || month > 12)
        return 0;

    if (month == 2 && is_leap_year(year))
        return 29;

    return days[month - 1];
}

static uint32_t local_time_to_unix_utc(uint16_t year,
                                       uint8_t month,
                                       uint8_t day,
                                       uint8_t hour,
                                       uint8_t min,
                                       uint8_t sec,
                                       int16_t timezone_offset_min)
{
    uint32_t days = 0;

    for (uint16_t y = 1970; y < year; y++)
        days += is_leap_year(y) ? 366 : 365;

    for (uint8_t m = 1; m < month; m++)
        days += days_in_month(year, m);

    days += day - 1;

    int64_t local_seconds = (int64_t)days * 86400
                          + (int64_t)hour * 3600
                          + (int64_t)min * 60
                          + sec;

    return (uint32_t)(local_seconds - (int64_t)timezone_offset_min * 60);
}

static void build_time_sync_payload(uint16_t year,
                                    uint8_t month,
                                    uint8_t day,
                                    uint8_t hour,
                                    uint8_t min,
                                    uint8_t sec,
                                    int16_t timezone_offset_min,
                                    uint8_t out[6])
{
    uint32_t unix_sec = local_time_to_unix_utc(
        year, month, day, hour, min, sec, timezone_offset_min
    );

    out[0] = (uint8_t)(unix_sec);
    out[1] = (uint8_t)(unix_sec >> 8);
    out[2] = (uint8_t)(unix_sec >> 16);
    out[3] = (uint8_t)(unix_sec >> 24);

    out[4] = (uint8_t)(timezone_offset_min);
    out[5] = (uint8_t)(timezone_offset_min >> 8);
}

int main(void)
{
    uint8_t payload[6];

    time_t now = time(NULL);
    struct tm local_tm;
    localtime_s(&local_tm, &now);

    build_time_sync_payload(
        local_tm.tm_year + 1900,   // 年
        local_tm.tm_mon + 1,       // 月 (0-11 -> 1-12)
        local_tm.tm_mday,          // 日
        local_tm.tm_hour,          // 时
        local_tm.tm_min,           // 分
        local_tm.tm_sec,           // 秒
        480,                       // 时区偏移(分钟)，UTC+8
        payload
    );

    printf("payload hex: ");
    for (int i = 0; i < 6; i++)
        printf("%02X", payload[i]);

    printf("\n");

    return 0;
}

可以直接编译成exe放在这边。