diff options
Diffstat (limited to 'solar.c')
| -rw-r--r-- | solar.c | 144 |
1 files changed, 70 insertions, 74 deletions
@@ -11,8 +11,6 @@ # pragma GCC diagnostic ignored "-Wunsuffixed-float-constants" #endif - - /* Select clock. */ #if defined(DO_NOT_USE_COARSEC_CLOCK) || !defined(CLOCK_REALTIME_COARSE) # ifdef CLOCK_REALTIME_COARSE @@ -21,30 +19,26 @@ # define CLOCK_REALTIME_COARSE CLOCK_REALTIME #endif - - /** - * Get current Julian Centuries time (100 Julian days since J2000.) - * - * @return The current Julian Centuries time. + * Get current Julian Centuries time (100 Julian days since J2000) * - * @throws 0 On success. - * @throws Any error specified for clock_gettime(3) on error. + * @param nowp Output parameter for the current Julian Centuries time + * @return 0 on success, -1 on failure + * @throws Any error specified for clock_gettime(3) on error */ static double -julian_centuries() +julian_centuries(double *nowp) { struct timespec now; - double tm; if (clock_gettime(CLOCK_REALTIME_COARSE, &now)) - return 0.0; - tm = (double)(now.tv_nsec) / 1000000000.0 + (double)(now.tv_sec); - tm = (tm / 86400.0 + 2440587.5 - 2451545.0) / 36525.0; - return errno = 0, tm; + return -1; + *nowp = (double)(now.tv_nsec) / 1000000000.0 + (double)(now.tv_sec); + *nowp = (*nowp / 86400.0 + 2440587.5 - 2451545.0) / 36525.0; + return 0; } /** - * Convert a Julian Centuries timestamp to a Julian Day timestamp. + * Convert a Julian Centuries timestamp to a Julian Day timestamp * * @param tm The time in Julian Centuries * @return The time in Julian Days @@ -57,7 +51,7 @@ julian_centuries_to_julian_day(double tm) /** - * Convert an angle (or otherwise) from degrees to radians. + * Convert an angle (or otherwise) from degrees to radians * * @param deg The angle in degrees. * @param The angle in radians. @@ -69,7 +63,7 @@ radians(double deg) } /** - * Convert an angle (or otherwise) from radians to degrees. + * Convert an angle (or otherwise) from radians to degrees * * @param rad The angle in radians. * @param The angle in degrees. @@ -84,11 +78,11 @@ degrees(double rad) /** * Calculates the Sun's elevation from the solar hour angle * - * @param longitude The longitude in degrees eastwards. - * from Greenwich, negative for westwards. - * @param declination The declination, in radians. - * @param hour_angle The solar hour angle, in radians. - * @return The Sun's elevation, in radians. + * @param longitude The longitude in degrees eastwards + * from Greenwich, negative for westwards + * @param declination The declination, in radians + * @param hour_angle The solar hour angle, in radians + * @return The Sun's elevation, in radians */ static inline double elevation_from_hour_angle(double latitude, double declination, double hour_angle) @@ -100,10 +94,10 @@ elevation_from_hour_angle(double latitude, double declination, double hour_angle } /** - * Calculates the Sun's geometric mean longitude. + * Calculates the Sun's geometric mean longitude * - * @param tm The time in Julian Centuries. - * @return The Sun's geometric mean longitude in radians. + * @param tm The time in Julian Centuries + * @return The Sun's geometric mean longitude in radians */ static inline double sun_geometric_mean_longitude(double tm) @@ -116,10 +110,10 @@ sun_geometric_mean_longitude(double tm) } /** - * Calculates the Sun's geometric mean anomaly. + * Calculates the Sun's geometric mean anomaly * - * @param tm The time in Julian Centuries. - * @return The Sun's geometric mean anomaly in radians. + * @param tm The time in Julian Centuries + * @return The Sun's geometric mean anomaly in radians */ static inline double sun_geometric_mean_anomaly(double tm) @@ -128,10 +122,10 @@ sun_geometric_mean_anomaly(double tm) } /** - * Calculates the Earth's orbit eccentricity. + * Calculates the Earth's orbit eccentricity * - * @param tm The time in Julian Centuries. - * @return The Earth's orbit eccentricity. + * @param tm The time in Julian Centuries + * @return The Earth's orbit eccentricity */ static inline double earth_orbit_eccentricity(double tm) @@ -141,10 +135,10 @@ earth_orbit_eccentricity(double tm) /** * Calculates the Sun's equation of the centre, the difference - * between the true anomaly and the mean anomaly. + * between the true anomaly and the mean anomaly * - * @param tm The time in Julian Centuries. - * @return The Sun's equation of the centre, in radians. + * @param tm The time in Julian Centuries + * @return The Sun's equation of the centre, in radians */ static inline double sun_equation_of_centre(double tm) @@ -157,10 +151,10 @@ sun_equation_of_centre(double tm) } /** - * Calculates the Sun's real longitudinal position. + * Calculates the Sun's real longitudinal position * - * @param tm The time in Julian Centuries. - * @return The longitude, in radians. + * @param tm The time in Julian Centuries + * @return The longitude, in radians */ static inline double sun_real_longitude(double tm) @@ -169,10 +163,10 @@ sun_real_longitude(double tm) } /** - * Calculates the Sun's apparent longitudinal position. + * Calculates the Sun's apparent longitudinal position * - * @param tm The time in Julian Centuries. - * @return The longitude, in radians. + * @param tm The time in Julian Centuries + * @return The longitude, in radians */ static inline double sun_apparent_longitude(double tm) @@ -183,10 +177,10 @@ sun_apparent_longitude(double tm) /** * Calculates the mean ecliptic obliquity of the Sun's - * apparent motion without variation correction. + * apparent motion without variation correction * - * @param tm The time in Julian Centuries. - * @return The uncorrected mean obliquity, in radians. + * @param tm The time in Julian Centuries + * @return The uncorrected mean obliquity, in radians */ static double mean_ecliptic_obliquity(double tm) @@ -197,10 +191,10 @@ mean_ecliptic_obliquity(double tm) /** * Calculates the mean ecliptic obliquity of the Sun's - * parent motion with variation correction. + * parent motion with variation correction * - * @param tm The time in Julian Centuries. - * @return The mean obliquity, in radians. + * @param tm The time in Julian Centuries + * @return The mean obliquity, in radians */ static double corrected_mean_ecliptic_obliquity(double tm) @@ -210,10 +204,10 @@ corrected_mean_ecliptic_obliquity(double tm) } /** - * Calculates the Sun's declination. + * Calculates the Sun's declination * - * @param tm The time in Julian Centuries. - * @return The Sun's declination, in radian. + * @param tm The time in Julian Centuries + * @return The Sun's declination, in radian */ static inline double solar_declination(double tm) @@ -224,10 +218,10 @@ solar_declination(double tm) /** * Calculates the equation of time, the discrepancy - * between apparent and mean solar time. + * between apparent and mean solar time * - * @param tm The time in Julian Centuries. - * @return The equation of time, in degrees. + * @param tm The time in Julian Centuries + * @return The equation of time, in degrees */ static inline double equation_of_time(double tm) @@ -245,15 +239,15 @@ equation_of_time(double tm) /** * Calculates the Sun's elevation as apparent - * from a geographical position. + * from a geographical position * - * @param tm The time in Julian Centuries. + * @param tm The time in Julian Centuries * @param latitude The latitude in degrees northwards from - * the equator, negative for southwards. + * the equator, negative for southwards * @param longitude The longitude in degrees eastwards from - * Greenwich, negative for westwards. + * Greenwich, negative for westwards * @return The Sun's apparent elevation at the specified time as seen - * from the specified position, measured in radians. + * from the specified position, measured in radians */ static inline double solar_elevation_from_time(double tm, double latitude, double longitude) @@ -265,35 +259,37 @@ solar_elevation_from_time(double tm, double latitude, double longitude) return elevation_from_hour_angle(latitude, solar_declination(tm), rc); } - /** * Calculates the Sun's elevation as apparent - * from a geographical position. + * from a geographical position * * @param latitude The latitude in degrees northwards from - * the equator, negative for southwards. + * the equator, negative for southwards * @param longitude The longitude in degrees eastwards from - * Greenwich, negative for westwards. - * @return The Sun's apparent elevation as seen, right now, - * from the specified position, measured in degrees. - * - * @throws 0 On success. - * @throws Any error specified for clock_gettime(3) on error. + * Greenwich, negative for westwards + * @param elevation Output parameter for the Sun's apparent elevation + * as seen, right now, from the specified position, + * measured in degrees + * @return 0 on success, -1 on failure + * @throws Any error specified for clock_gettime(3) on error */ double -libred_solar_elevation(double latitude, double longitude) +libred_solar_elevation(double latitude, double longitude, double *elevation) { - double tm = julian_centuries(); - return errno ? -1 : degrees(solar_elevation_from_time(tm, latitude, longitude)); + double tm; + if (julian_centuries(&tm)) + return -1; + *elevation = degrees(solar_elevation_from_time(tm, latitude, longitude)); + return 0; } - /** - * Exit if time the is before year 0 in J2000. + * Exit if time the is before year 0 in J2000 * - * @return 0 on success, -1 on error. + * @return 0 on success, -1 on error */ -int libred_check_timetravel(void) +int +libred_check_timetravel(void) { #if !defined(TIMETRAVELLER) struct timespec now; |