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      1 /*	$NetBSD: ntp_calgps.h,v 1.2 2020/05/25 20:47:19 christos Exp $	*/
      2 
      3 /*
      4  * ntp_calgps.h - calendar for GPS/GNSS based clocks
      5  *
      6  * Written by Juergen Perlinger (perlinger (at) ntp.org) for the NTP project.
      7  * The contents of 'html/copyright.html' apply.
      8  *
      9  * --------------------------------------------------------------------
     10  *
     11  * This module implements stuff often used with GPS/GNSS receivers
     12  */
     13 #ifndef NTP_CALGPS_H
     14 #define NTP_CALGPS_H
     15 
     16 #include <time.h>
     17 
     18 #include "ntp_types.h"
     19 #include "ntp_fp.h"
     20 #include "ntp_calendar.h"
     21 
     22 /* GPS week calendar (extended weeks)
     23  * We use weeks based on 1899-31-12, which was the last Sunday before
     24  * the begin of the NTP epoch. (Which is equivalent to saying 1900-01-01
     25  * was a Monday...)
     26  *
     27  * We simply pre-calculate the offsets and cycle shifts for the real GPS
     28  * calendar, which starts at 1980-01-06, to simplyfy some expressions.
     29  *
     30  * This has a fringe benefit that should not be overlooked: Since week zero
     31  * is around 1900, and we should never have to deal with dates before
     32  * 1970 or 1980, a week number of zero can be easily used to indicate
     33  * an invalid week time stamp.
     34  */
     35 #define GPSNTP_WSHIFT	4175	/* weeks 1899-31-12 --> 1980-01-06 */
     36 #define GPSNTP_WCYCLE	  79	/* above, modulo 1024 */
     37 #define GPSNTP_DSHIFT	   1	/* day number of 1900-01-01 in week */
     38 
     39 struct gpsdatum {
     40 	uint32_t weeks;		/* weeks since GPS epoch	*/
     41 	int32_t  wsecs;		/* seconds since week start	*/
     42 	uint32_t frac;		/* fractional seconds		*/
     43 };
     44 typedef struct gpsdatum TGpsDatum;
     45 typedef struct gpsdatum const TcGpsDatum;
     46 
     47 /* NTP date/time in split representation */
     48 struct ntpdatum {
     49 	uint32_t days;		/* since NTP epoch		*/
     50 	int32_t  secs;		/* since midnight, denorm is ok */
     51 	uint32_t frac;		/* fractional seconds		*/
     52 };
     53 typedef struct ntpdatum TNtpDatum;
     54 typedef struct ntpdatum const TcNtpDatum;
     55 
     56 /*
     57  * GPS week/sec calendar functions
     58  *
     59  * see the implementation for details, especially the
     60  * 'gpscal_from_weektime{1,2}()'
     61  */
     62 
     63 extern TGpsDatum
     64 gpscal_fix_gps_era(TcGpsDatum *);
     65 
     66 extern void
     67 gpscal_add_offset(TGpsDatum *datum, l_fp offset);
     68 
     69 extern TGpsDatum
     70 gpscal_from_calendar_ex(TcCivilDate*, l_fp fofs, int/*BOOL*/ warp);
     71 
     72 static inline TGpsDatum
     73 gpscal_from_calendar(TcCivilDate *pCiv, l_fp fofs) {
     74     return gpscal_from_calendar_ex(pCiv, fofs, TRUE);
     75 }
     76 
     77 extern TGpsDatum 	/* see source for semantic of the 'fofs' value! */
     78 gpscal_from_gpsweek(uint16_t w, int32_t s, l_fp fofs);
     79 
     80 extern TGpsDatum
     81 gpscal_from_weektime1(int32_t wsecs, l_fp fofs, l_fp pivot);
     82 
     83 extern TGpsDatum
     84 gpscal_from_weektime2(int32_t wsecs, l_fp fofs,	TcGpsDatum *pivot);
     85 
     86 extern void
     87 gpscal_to_calendar(TCivilDate*, TcGpsDatum*);
     88 
     89 extern TGpsDatum
     90 gpscal_from_gpsntp(TcNtpDatum*);
     91 
     92 extern l_fp
     93 ntpfp_from_gpsdatum(TcGpsDatum *);
     94 
     95 /*
     96  * NTP day/sec calendar functions
     97  *
     98  * see the implementation for details, especially the
     99  * 'gpscal_from_daytime{1,2}()'
    100  */
    101 extern TNtpDatum
    102 gpsntp_fix_gps_era(TcNtpDatum *);
    103 
    104 extern void
    105 gpsntp_add_offset(TNtpDatum *datum, l_fp offset);
    106 
    107 extern TNtpDatum
    108 gpsntp_from_calendar_ex(TcCivilDate*, l_fp fofs, int/*BOOL*/ warp);
    109 
    110 static inline TNtpDatum
    111 gpsntp_from_calendar(TcCivilDate * pCiv, l_fp fofs) {
    112 	return gpsntp_from_calendar_ex(pCiv, fofs, TRUE);
    113 }
    114 
    115 extern TNtpDatum
    116 gpsntp_from_daytime1_ex(TcCivilDate *dt, l_fp fofs, l_fp pivot, int/*BOOL*/ warp);
    117 
    118 static inline TNtpDatum
    119 gpsntp_from_daytime1(TcCivilDate *dt, l_fp fofs, l_fp pivot) {
    120 	return gpsntp_from_daytime1_ex(dt, fofs, pivot, TRUE);
    121 }
    122 
    123 extern TNtpDatum
    124 gpsntp_from_daytime2_ex(TcCivilDate *dt, l_fp fofs, TcNtpDatum *pivot, int/*BOOL*/ warp);
    125 
    126 static inline TNtpDatum
    127 gpsntp_from_daytime2(TcCivilDate *dt, l_fp fofs, TcNtpDatum *pivot) {
    128 	return gpsntp_from_daytime2_ex(dt, fofs, pivot, TRUE);
    129 }
    130 
    131 extern TNtpDatum
    132 gpsntp_from_gpscal_ex(TcGpsDatum*, int/*BOOL*/ warp);
    133 
    134 static inline TNtpDatum
    135 gpsntp_from_gpscal(TcGpsDatum *wd) {
    136 	return gpsntp_from_gpscal_ex(wd, FALSE);
    137 }
    138 
    139 extern void
    140 gpsntp_to_calendar(TCivilDate*, TcNtpDatum*);
    141 
    142 extern l_fp
    143 ntpfp_from_ntpdatum(TcNtpDatum*);
    144 
    145 /*
    146  * Some helpers
    147  */
    148 
    149 /* apply fudge to time stamp: *SUBTRACT* the given offset from an l_fp*/
    150 extern l_fp
    151 ntpfp_with_fudge(l_fp lfp, double ofs);
    152 
    153 #endif /*!defined(NTP_CALGPS_H)*/
    154