diff options
Diffstat (limited to 'watch-library/shared/watch/watch_utility.c')
| -rw-r--r-- | watch-library/shared/watch/watch_utility.c | 67 |
1 files changed, 57 insertions, 10 deletions
diff --git a/watch-library/shared/watch/watch_utility.c b/watch-library/shared/watch/watch_utility.c index 252624b3..6a8b408a 100644 --- a/watch-library/shared/watch/watch_utility.c +++ b/watch-library/shared/watch/watch_utility.c @@ -26,16 +26,60 @@ #include "watch_utility.h" const char * watch_utility_get_weekday(watch_date_time date_time) { - static const char weekdays[7][3] = {"SA", "SU", "MO", "TU", "WE", "TH", "FR"}; - date_time.unit.year += 20; - if (date_time.unit.month <= 2) { - date_time.unit.month += 12; - date_time.unit.year--; + static const char weekdays[7][3] = {"MO", "TU", "WE", "TH", "FR", "SA", "SU"}; + return weekdays[watch_utility_get_iso8601_weekday_number(date_time.unit.year + WATCH_RTC_REFERENCE_YEAR, date_time.unit.month, date_time.unit.day) - 1]; +} + +// Per ISO8601 week starts on Monday with index 1 +uint8_t watch_utility_get_iso8601_weekday_number(uint16_t year, uint8_t month, uint8_t day) { + year -= WATCH_RTC_REFERENCE_YEAR; + year += 20; + if (month <= 2) { + month += 12; + year--; } - return weekdays[(date_time.unit.day + 13 * (date_time.unit.month + 1) / 5 + date_time.unit.year + date_time.unit.year / 4 + 525) % 7]; + return ((day + (13 * (month + 1) / 5) + year + (year / 4) + 5) % 7) + 1; } -uint32_t watch_utility_convert_to_unix_time(uint16_t year, uint8_t month, uint8_t day, uint8_t hour, uint8_t minute, uint8_t second, uint32_t utc_offset) { +// this function is from the excellent musl c library +uint8_t watch_utility_get_weeknumber(uint16_t year, uint8_t month, uint8_t day) { + uint8_t weekday; + uint16_t days; + + weekday = watch_utility_get_iso8601_weekday_number(year, month, day) % 7; + days = watch_utility_days_since_new_year(year, month, day); + + int val = (days + 7U - (weekday+6U)%7) / 7; + /* If 1 Jan is just 1-3 days past Monday, + * the previous week is also in this year. */ + if ((weekday + 371U - days - 2) % 7 <= 2) + val++; + if (!val) { + val = 52; + /* If 31 December of prev year a Thursday, + * or Friday of a leap year, then the + * prev year has 53 weeks. */ + int dec31 = (weekday + 7U - days - 1) % 7; + if (dec31 == 4 || (dec31 == 5 && is_leap(year%400-1))) + val++; + } else if (val == 53) { + /* If 1 January is not a Thursday, and not + * a Wednesday of a leap year, then this + * year has only 52 weeks. */ + int jan1 = (weekday + 371U - days) % 7; + if (jan1 != 4 && (jan1 != 3 || !is_leap(year))) + val = 1; + } + return val; +} + +uint8_t is_leap(uint16_t y) +{ + y += 1900; + return !(y%4) && ((y%100) || !(y%400)); +} + +uint16_t watch_utility_days_since_new_year(uint16_t year, uint8_t month, uint8_t day) { uint16_t DAYS_SO_FAR[] = { 0, // Jan 31, // Feb @@ -51,10 +95,13 @@ uint32_t watch_utility_convert_to_unix_time(uint16_t year, uint8_t month, uint8_ 334 // December }; + return (is_leap(year) && (month > 2) ? 1 : 0) + DAYS_SO_FAR[month - 1] + day; +} + +uint32_t watch_utility_convert_to_unix_time(uint16_t year, uint8_t month, uint8_t day, uint8_t hour, uint8_t minute, uint8_t second, uint32_t utc_offset) { uint32_t year_adj = year + 4800; - uint32_t febs = year_adj - (month <= 2 ? 1 : 0); /* Februaries since base. */ - uint32_t leap_days = 1 + (febs / 4) - (febs / 100) + (febs / 400); - uint32_t days = 365 * year_adj + leap_days + DAYS_SO_FAR[month - 1] + day - 1; + uint32_t leap_days = 1 + (year_adj / 4) - (year_adj / 100) + (year_adj / 400); + uint32_t days = 365 * year_adj + leap_days + watch_utility_days_since_new_year(year, month, day) - 1; days -= 2472692; /* Adjust to Unix epoch. */ uint32_t timestamp = days * 86400; |