calendar.c

#include <stdint.h>
#include <stdbool.h>
#include "calendar.h"

void epochToDateTime(uint32_t seconds, time_t *const tm)
{
  const uint8_t daysInMonth[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
  uint8_t dim;
  uint16_t daysInYear;
  uint32_t minutes, hours, days, year, month, dayOfWeek;
  bool leapYear;
  /* calculate minutes */
  minutes = seconds / 60;
  seconds -= minutes * 60;
  /* calculate hours */
  hours = minutes / 60;
  minutes -= hours * 60;
  /* calculate days */
  days = hours / 24;
  hours -= days * 24;
  /* Unix time starts in 1970 on a Thursday */
  year = 1970;
  dayOfWeek = 4;
  while (1)
  {
    leapYear = (year % 4 == 0 && (year % 100 != 0 || year % 400 == 0));
    daysInYear = leapYear ? 366 : 365;
    if (days >= daysInYear)
    {
      dayOfWeek += leapYear ? 2 : 1;
      days -= daysInYear;
      if (dayOfWeek >= 7)
        dayOfWeek -= 7;
      ++year;
    }
    else
    {
      tm->tm_yday = days;
      dayOfWeek += days;
      dayOfWeek %= 7;
      /* calculate the month and day */
      for (month = 0; month < 12; month++)
      {
        dim = daysInMonth[month];
        /* add a day to February if this is a leap year */
        if (month == 1 && leapYear)
          ++dim;
        if (days >= dim)
          days -= dim;
        else
          break;
      }
      break;
    }
  }
  tm->tm_sec = seconds;
  tm->tm_min = minutes;
  tm->tm_hour = hours;
  tm->tm_mday = days + 1;
  tm->tm_mon = month;
  tm->tm_year = year;
  tm->tm_wday = dayOfWeek;
}

static const uint32_t lunar200y[199] = {
    0x04AE53, 0x0A5748, 0x5526BD, 0x0D2650, 0x0D9544, 0x46AAB9, 0x056A4D, 0x09AD42, 0x24AEB6, 0x04AE4A, /*1901-1910*/
    0x6A4DBE, 0x0A4D52, 0x0D2546, 0x5D52BA, 0x0B544E, 0x0D6A43, 0x296D37, 0x095B4B, 0x749BC1, 0x049754, /*1911-1920*/
    0x0A4B48, 0x5B25BC, 0x06A550, 0x06D445, 0x4ADAB8, 0x02B64D, 0x095742, 0x2497B7, 0x04974A, 0x664B3E, /*1921-1930*/
    0x0D4A51, 0x0EA546, 0x56D4BA, 0x05AD4E, 0x02B644, 0x393738, 0x092E4B, 0x7C96BF, 0x0C9553, 0x0D4A48, /*1931-1940*/
    0x6DA53B, 0x0B554F, 0x056A45, 0x4AADB9, 0x025D4D, 0x092D42, 0x2C95B6, 0x0A954A, 0x7B4ABD, 0x06CA51, /*1941-1950*/
    0x0B5546, 0x555ABB, 0x04DA4E, 0x0A5B43, 0x352BB8, 0x052B4C, 0x8A953F, 0x0E9552, 0x06AA48, 0x6AD53C, /*1951-1960*/
    0x0AB54F, 0x04B645, 0x4A5739, 0x0A574D, 0x052642, 0x3E9335, 0x0D9549, 0x75AABE, 0x056A51, 0x096D46, /*1961-1970*/
    0x54AEBB, 0x04AD4F, 0x0A4D43, 0x4D26B7, 0x0D254B, 0x8D52BF, 0x0B5452, 0x0B6A47, 0x696D3C, 0x095B50, /*1971-1980*/
    0x049B45, 0x4A4BB9, 0x0A4B4D, 0xAB25C2, 0x06A554, 0x06D449, 0x6ADA3D, 0x0AB651, 0x093746, 0x5497BB, /*1981-1990*/
    0x04974F, 0x064B44, 0x36A537, 0x0EA54A, 0x86B2BF, 0x05AC53, 0x0AB647, 0x5936BC, 0x092E50, 0x0C9645, /*1991-2000*/
    0x4D4AB8, 0x0D4A4C, 0x0DA541, 0x25AAB6, 0x056A49, 0x7AADBD, 0x025D52, 0x092D47, 0x5C95BA, 0x0A954E, /*2001-2010*/
    0x0B4A43, 0x4B5537, 0x0AD54A, 0x955ABF, 0x04BA53, 0x0A5B48, 0x652BBC, 0x052B50, 0x0A9345, 0x474AB9, /*2011-2020*/
    0x06AA4C, 0x0AD541, 0x24DAB6, 0x04B64A, 0x69573D, 0x0A4E51, 0x0D2646, 0x5E933A, 0x0D534D, 0x05AA43, /*2021-2030*/
    0x36B537, 0x096D4B, 0xB4AEBF, 0x04AD53, 0x0A4D48, 0x6D25BC, 0x0D254F, 0x0D5244, 0x5DAA38, 0x0B5A4C, /*2031-2040*/
    0x056D41, 0x24ADB6, 0x049B4A, 0x7A4BBE, 0x0A4B51, 0x0AA546, 0x5B52BA, 0x06D24E, 0x0ADA42, 0x355B37, /*2041-2050*/
    0x09374B, 0x8497C1, 0x049753, 0x064B48, 0x66A53C, 0x0EA54F, 0x06B244, 0x4AB638, 0x0AAE4C, 0x092E42, /*2051-2060*/
    0x3C9735, 0x0C9649, 0x7D4ABD, 0x0D4A51, 0x0DA545, 0x55AABA, 0x056A4E, 0x0A6D43, 0x452EB7, 0x052D4B, /*2061-2070*/
    0x8A95BF, 0x0A9553, 0x0B4A47, 0x6B553B, 0x0AD54F, 0x055A45, 0x4A5D38, 0x0A5B4C, 0x052B42, 0x3A93B6, /*2071-2080*/
    0x069349, 0x7729BD, 0x06AA51, 0x0AD546, 0x54DABA, 0x04B64E, 0x0A5743, 0x452738, 0x0D264A, 0x8E933E, /*2081-2090*/
    0x0D5252, 0x0DAA47, 0x66B53B, 0x056D4F, 0x04AE45, 0x4A4EB9, 0x0A4D4C, 0x0D1541, 0x2D92B5            /*2091-2099*/
};
static const int monthTotal[13] = {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365};
void solarToLunar(const time_t *const solar, lunar_t *const lunar)
{
  uint16_t year = solar->tm_year;
  uint16_t month = solar->tm_mon + 1;
  uint16_t day = solar->tm_mday;
  uint16_t bySpring, bySolar;
  uint8_t index, flag, daysPerMonth;

  //bySpring 记录春节离当年元旦的天数。
  //bySolar 记录阳历日离当年元旦的天数。
  if (((lunar200y[year - 1901] & 0x0060) >> 5) == 1)
    bySpring = (lunar200y[year - 1901] & 0x001F) - 1;
  else
    bySpring = (lunar200y[year - 1901] & 0x001F) - 1 + 31;
  bySolar = monthTotal[month - 1] + day - 1;
  if ((!(year % 4)) && (month > 2))
    bySolar++;

  //daysPerMonth记录大小月的天数 29 或30
  //index 记录从哪个月开始来计算。
  //flag 是用来对闰月的特殊处理。

  //判断阳历日在春节前还是春节后
  if (bySolar >= bySpring) //阳历日在春节后（含春节那天）
  {
    bySolar -= bySpring;
    month = 1;
    index = 1;
    flag = 0;
    if ((lunar200y[year - 1901] & (0x80000 >> (index - 1))) == 0)
      daysPerMonth = 29;
    else
      daysPerMonth = 30;
    while (bySolar >= daysPerMonth)
    {
      bySolar -= daysPerMonth;
      index++;
      if (month == ((lunar200y[year - 1901] & 0xF00000) >> 20))
      {
        flag = ~flag;
        if (flag == 0)
          month++;
      }
      else
        month++;
      if ((lunar200y[year - 1901] & (0x80000 >> (index - 1))) == 0)
        daysPerMonth = 29;
      else
        daysPerMonth = 30;
    }
    day = bySolar + 1;
  }
  else //阳历日在春节前
  {
    bySpring -= bySolar;
    year--;
    month = 12;
    if (((lunar200y[year - 1901] & 0xF00000) >> 20) == 0)
      index = 12;
    else
      index = 13;
    flag = 0;
    if ((lunar200y[year - 1901] & (0x80000 >> (index - 1))) == 0)
      daysPerMonth = 29;
    else
      daysPerMonth = 30;
    while (bySpring > daysPerMonth)
    {
      bySpring -= daysPerMonth;
      index--;
      if (flag == 0)
        month--;
      if (month == ((lunar200y[year - 1901] & 0xF00000) >> 20))
        flag = ~flag;
      if ((lunar200y[year - 1901] & (0x80000 >> (index - 1))) == 0)
        daysPerMonth = 29;
      else
        daysPerMonth = 30;
    }

    day = daysPerMonth - bySpring + 1;
  }
  lunar->day = day;
  lunar->month = month;
  lunar->year = year;
  if (month == ((lunar200y[year - 1901] & 0xF00000) >> 20))
    lunar->reserved = 1;
  else
    lunar->reserved = 0;
}