2 * ntp_calendar.h - definitions for the calendar time-of-day routine
11 /* gregorian calendar date */
13 uint16_t year; /* year (A.D.) */
14 uint16_t yearday; /* day of year, 1 = January 1 */
15 uint8_t month; /* month, 1 = January */
16 uint8_t monthday; /* day of month */
17 uint8_t hour; /* hour of day, midnight = 0 */
18 uint8_t minute; /* minute of hour */
19 uint8_t second; /* second of minute */
20 uint8_t weekday; /* 0..7, 0=Sunday */
22 typedef struct calendar TCivilDate;
23 typedef struct calendar const TcCivilDate;
25 /* ISO week calendar date */
27 uint16_t year; /* year (A.D.) */
28 uint8_t week; /* 1..53, week in year */
29 uint8_t weekday; /* 1..7, 1=Monday */
30 uint8_t hour; /* hour of day, midnight = 0 */
31 uint8_t minute; /* minute of hour */
32 uint8_t second; /* second of minute */
34 typedef struct isodate TIsoDate;
35 typedef struct isodate const TcIsoDate;
37 /* general split representation */
43 typedef time_t (*systime_func_ptr)(time_t *);
46 * set the function for getting the system time. This is mostly used for
47 * unit testing to provide a fixed / shifted time stamp. Setting the
48 * value to NULL restores the original function, that is, 'time()',
49 * which is also the automatic default.
51 extern systime_func_ptr ntpcal_set_timefunc(systime_func_ptr);
59 #define CAL_WEDNESDAY 3
60 #define CAL_THURSDAY 4
62 #define CAL_SATURDAY 6
63 #define CAL_SUNDAY7 7 /* also sunday */
66 * Days in each month. 30 days hath September...
83 * We deal in a 4 year cycle starting at March 1, 1900. We assume
84 * we will only want to deal with dates since then, and not to exceed
85 * the rollover day in 2036.
87 #define SECSPERMIN (60) /* seconds per minute */
88 #define MINSPERHR (60) /* minutes per hour */
89 #define HRSPERDAY (24) /* hours per day */
90 #define DAYSPERWEEK (7) /* days per week */
91 #define DAYSPERYEAR (365) /* days per year */
93 #define SECSPERHR (SECSPERMIN * MINSPERHR)
94 #define SECSPERDAY (SECSPERHR * HRSPERDAY)
95 #define SECSPERWEEK (DAYSPERWEEK * SECSPERDAY)
96 #define SECSPERYEAR (365 * SECSPERDAY) /* regular year */
97 #define SECSPERLEAPYEAR (366 * SECSPERDAY) /* leap year */
98 #define SECSPERAVGYEAR 31556952 /* mean year length over 400yrs */
100 #define GPSWEEKS 1024 /* GPS week cycle */
102 * Gross hacks. I have illicit knowlege that there won't be overflows
103 * here, the compiler often can't tell this.
105 #define TIMES60(val) ((((val)<<4) - (val))<<2) /* *(16 - 1) * 4 */
106 #define TIMES24(val) (((val)<<4) + ((val)<<3)) /* *16 + *8 */
107 #define TIMES7(val) (((val)<<3) - (val)) /* *8 - *1 */
108 #define TIMESDPERC(val) (((val)<<10) + ((val)<<8) \
109 + ((val)<<7) + ((val)<<5) \
110 + ((val)<<4) + ((val)<<2) + (val)) /* *big* hack */
113 extern const char * const months[12];
114 extern const char * const daynames[7];
116 extern char * ntpcal_iso8601std(char*, size_t, struct calendar const*);
117 extern void caljulian (uint32_t, struct calendar *);
118 extern uint32_t caltontp (const struct calendar *);
121 * Convert between 'time_t' and 'vint64'
123 extern vint64 time_to_vint64(const time_t *);
124 extern time_t vint64_to_time(const vint64 *);
127 * Get the build date & time. ATTENTION: The time zone is not specified!
128 * This depends entirely on the C compilers' capabilities to properly
129 * expand the '__TIME__' and '__DATE__' macros, as required by the C
133 ntpcal_get_build_date(struct calendar * /* jd */);
136 * Convert a timestamp in NTP scale to a time_t value in the UN*X
137 * scale with proper epoch unfolding around a given pivot or the
138 * current system time.
141 ntpcal_ntp_to_time(uint32_t /* ntp */, const time_t * /* pivot */);
144 * Convert a timestamp in NTP scale to a 64bit seconds value in the NTP
145 * scale with proper epoch unfolding around a given pivot or the current
147 * Note: The pivot must be given in UN*X time scale!
150 ntpcal_ntp_to_ntp(uint32_t /* ntp */, const time_t * /* pivot */);
153 * Split a time stamp in seconds into elapsed days and elapsed seconds
157 ntpcal_daysplit(const vint64 *);
160 * Split a time stamp in seconds into elapsed weeks and elapsed seconds
161 * since start of week.
164 ntpcal_weeksplit(const vint64 *);
167 * Merge a number of days and a number of seconds into seconds,
168 * expressed in 64 bits to avoid overflow.
171 ntpcal_dayjoin(int32_t /* days */, int32_t /* seconds */);
174 * Merge a number of weeks and a number of seconds into seconds,
175 * expressed in 64 bits to avoid overflow.
178 ntpcal_weekjoin(int32_t /* weeks */, int32_t /* seconds */);
180 /* Get the number of leap years since epoch for the number of elapsed
184 ntpcal_leapyears_in_years(int32_t /* years */);
187 * Convert elapsed years in Era into elapsed days in Era.
190 ntpcal_days_in_years(int32_t /* years */);
193 * Convert a number of elapsed month in a year into elapsed days
196 * The month will be normalized, and 'res.hi' will contain the
197 * excessive years that must be considered when converting the years,
198 * while 'res.lo' will contain the days since start of the
199 * year. (Expect the resulting days to be negative, with a positive
200 * excess! But then, we need no leap year flag, either...)
203 ntpcal_days_in_months(int32_t /* months */);
206 * Convert ELAPSED years/months/days of gregorian calendar to elapsed
207 * days in Gregorian epoch. No range checks done here!
210 ntpcal_edate_to_eradays(int32_t /* years */, int32_t /* months */, int32_t /* mdays */);
213 * Convert a time spec to seconds. No range checks done here!
216 ntpcal_etime_to_seconds(int32_t /* hours */, int32_t /* minutes */, int32_t /* seconds */);
219 * Convert ELAPSED years/months/days of gregorian calendar to elapsed
222 * Note: This will give the true difference to the start of the given year,
223 * even if months & days are off-scale.
226 ntpcal_edate_to_yeardays(int32_t /* years */, int32_t /* months */, int32_t /* mdays */);
229 * Convert the date part of a 'struct tm' (that is, year, month,
230 * day-of-month) into the RataDie of that day.
233 ntpcal_tm_to_rd(const struct tm * /* utm */);
236 * Convert the date part of a 'struct calendar' (that is, year, month,
237 * day-of-month) into the RataDie of that day.
240 ntpcal_date_to_rd(const struct calendar * /* jt */);
243 * Given the number of elapsed days in the calendar era, split this
244 * number into the number of elapsed years in 'res.quot' and the
245 * number of elapsed days of that year in 'res.rem'.
247 * if 'isleapyear' is not NULL, it will receive an integer that is 0
248 * for regular years and a non-zero value for leap years.
250 * The input is limited to [-2^30, 2^30-1]. If the days exceed this
251 * range, errno is set to EDOM and the result is saturated.
254 ntpcal_split_eradays(int32_t /* days */, int/*BOOL*/ * /* isleapyear */);
257 * Given a number of elapsed days in a year and a leap year indicator,
258 * split the number of elapsed days into the number of elapsed months
259 * in 'res.quot' and the number of elapsed days of that month in
263 ntpcal_split_yeardays(int32_t /* eyd */, int/*BOOL*/ /* isleapyear */);
266 * Convert a RataDie number into the date part of a 'struct
267 * calendar'. Return 0 if the year is regular year, !0 if the year is
271 ntpcal_rd_to_date(struct calendar * /* jt */, int32_t /* rd */);
274 * Convert a RataDie number into the date part of a 'struct
275 * tm'. Return 0 if the year is regular year, !0 if the year is a leap
279 ntpcal_rd_to_tm(struct tm * /* utm */, int32_t /* rd */);
282 * Take a value of seconds since midnight and split it into hhmmss in
283 * a 'struct calendar'. Return excessive days.
286 ntpcal_daysec_to_date(struct calendar * /* jt */, int32_t /* secs */);
289 * Take the time part of a 'struct calendar' and return the seconds
293 ntpcal_date_to_daysec(const struct calendar *);
296 * Take a value of seconds since midnight and split it into hhmmss in
297 * a 'struct tm'. Return excessive days.
300 ntpcal_daysec_to_tm(struct tm * /* utm */, int32_t /* secs */);
303 ntpcal_tm_to_daysec(const struct tm * /* utm */);
306 * convert a year number to rata die of year start
309 ntpcal_year_to_ystart(int32_t /* year */);
312 * For a given RataDie, get the RataDie of the associated year start,
313 * that is, the RataDie of the last January,1st on or before that day.
316 ntpcal_rd_to_ystart(int32_t /* rd */);
319 * convert a RataDie to the RataDie of start of the calendar month.
322 ntpcal_rd_to_mstart(int32_t /* year */);
326 ntpcal_daysplit_to_date(struct calendar * /* jt */,
327 const ntpcal_split * /* ds */, int32_t /* dof */);
330 ntpcal_daysplit_to_tm(struct tm * /* utm */, const ntpcal_split * /* ds */,
334 ntpcal_time_to_date(struct calendar * /* jd */, const vint64 * /* ts */);
337 ntpcal_periodic_extend(int32_t /* pivot */, int32_t /* value */,
338 int32_t /* cycle */);
341 ntpcal_ntp64_to_date(struct calendar * /* jd */, const vint64 * /* ntp */);
344 ntpcal_ntp_to_date(struct calendar * /* jd */, uint32_t /* ntp */,
345 const time_t * /* pivot */);
348 ntpcal_date_to_ntp64(const struct calendar * /* jd */);
351 ntpcal_date_to_ntp(const struct calendar * /* jd */);
354 ntpcal_date_to_time(const struct calendar * /* jd */);
357 * ISO week-calendar conversions
360 isocal_weeks_in_years(int32_t /* years */);
363 * The input is limited to [-2^30, 2^30-1]. If the weeks exceed this
364 * range, errno is set to EDOM and the result is saturated.
367 isocal_split_eraweeks(int32_t /* weeks */);
370 isocal_ntp64_to_date(struct isodate * /* id */, const vint64 * /* ntp */);
373 isocal_ntp_to_date(struct isodate * /* id */, uint32_t /* ntp */,
374 const time_t * /* pivot */);
377 isocal_date_to_ntp64(const struct isodate * /* id */);
380 isocal_date_to_ntp(const struct isodate * /* id */);
384 * day-of-week calculations
386 * Given a RataDie and a day-of-week, calculate a RDN that is reater-than,
387 * greater-or equal, closest, less-or-equal or less-than the given RDN
388 * and denotes the given day-of-week
391 ntpcal_weekday_gt(int32_t /* rdn */, int32_t /* dow */);
394 ntpcal_weekday_ge(int32_t /* rdn */, int32_t /* dow */);
397 ntpcal_weekday_close(int32_t /* rdn */, int32_t /* dow */);
400 ntpcal_weekday_le(int32_t /* rdn */, int32_t /* dow */);
403 ntpcal_weekday_lt(int32_t /* rdn */, int32_t /* dow */);
407 * handling of base date spec
410 basedate_eval_buildstamp(void);
413 basedate_eval_string(const char *str);
416 basedate_set_day(int32_t dayno);
419 basedate_get_day(void);
422 basedate_get_eracenter(void);
425 basedate_get_erabase(void);
428 basedate_get_gpsweek(void);
431 basedate_expand_gpsweek(unsigned short weekno);
434 * Additional support stuff for Ed Rheingold's calendrical calculations
438 * Start day of NTP time as days past 0000-12-31 in the proleptic
439 * Gregorian calendar. (So 0001-01-01 is day number 1; this is the Rata
440 * Die counting scheme used by Ed Rheingold in his book "Calendrical
443 #define DAY_NTP_STARTS 693596
446 * Start day of the UNIX epoch. This is the Rata Die of 1970-01-01.
448 #define DAY_UNIX_STARTS 719163
451 * Start day of the GPS epoch. This is the Rata Die of 1980-01-06
453 #define DAY_GPS_STARTS 722820
456 * Difference between UN*X and NTP epoch (25567).
458 #define NTP_TO_UNIX_DAYS (DAY_UNIX_STARTS - DAY_NTP_STARTS)
461 * Difference between GPS and NTP epoch (29224)
463 #define NTP_TO_GPS_DAYS (DAY_GPS_STARTS - DAY_NTP_STARTS)
466 * Days in a normal 4 year leap year calendar cycle (1461).
468 #define GREGORIAN_NORMAL_LEAP_CYCLE_DAYS (4 * 365 + 1)
471 * Days in a normal 100 year leap year calendar (36524). We lose a
472 * leap day in years evenly divisible by 100 but not by 400.
474 #define GREGORIAN_NORMAL_CENTURY_DAYS \
475 (25 * GREGORIAN_NORMAL_LEAP_CYCLE_DAYS - 1)
478 * The Gregorian calendar is based on a 400 year cycle. This is the
479 * number of days in each cycle (146097). We gain a leap day in years
480 * divisible by 400 relative to the "normal" century.
482 #define GREGORIAN_CYCLE_DAYS (4 * GREGORIAN_NORMAL_CENTURY_DAYS + 1)
485 * Number of weeks in 400 years (20871).
487 #define GREGORIAN_CYCLE_WEEKS (GREGORIAN_CYCLE_DAYS / 7)
490 * Is a Greogorian calendar year a leap year? The obvious solution is to
491 * test the expression
493 * (y % 4 == 0) && ((y % 100 != 0) || (y % 400 == 0))
495 * This needs (in theory) 2 true divisions -- most compilers check the
496 * (mod 4) condition by doing a bit test. Some compilers have been
497 * even observed to partially fuse the (mod 100) and (mod 400) test,
498 * but there is an alternative formula that gives the compiler even
501 * (y % 4 == 0) && ((y % 16 == 0) || (y % 25 != 0))
503 * The order of checks is chosen so that the shorcut evaluation can fix
504 * the result as soon as possible. And the compiler has to do only one
505 * true division here -- the (mod 4) and (mod 16) can be done with
506 * direct bit tests. *If* the compiler chooses to do so.
508 * The deduction is as follows: rewrite the standard formula as
509 * (y % 4 == 0) && ((y % 4*25 != 0) || (y % 16*25 == 0))
511 * then split the congruences:
512 * (y % 4 == 0) && ((y % 4 != 0 || y % 25 != 0) || (y % 16 == 0 && y % 25 == 0))
514 * eliminate the 1st inner term, as it is provably false:
515 * (y % 4 == 0) && (y % 25 != 0 || (y % 16 == 0 && y % 25 == 0))
517 * Use the distributive laws on the second major group:
518 * (y % 4 == 0) && ((y % 25 != 0 || y % 16 == 0) && (y % 25 != 0 || y % 25 == 0))
520 * Eliminate the constant term, reorder, and voila:
524 is_leapyear(int32_t y) {
525 return !(y % 4) && (!(y % 16) || (y % 25));
527 /* The (mod 4) test eliminates 3/4 (or 12/16) of all values.
528 * The (mod 16) test eliminates another 1/16 of all values.
529 * 3/16 of all values reach the final division.
530 * Assuming that the true division is the most costly operation, this
531 * sequence should give most bang for the buck.
535 extern int u32mod7(uint32_t x);
536 extern int i32mod7(int32_t x);
537 extern uint32_t i32fmod(int32_t x, uint32_t d);
539 extern int32_t ntpcal_expand_century(uint32_t y, uint32_t m, uint32_t d, uint32_t wd);