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Diffstat (limited to 'ast/erfa/dtf2d.c')
| -rw-r--r-- | ast/erfa/dtf2d.c | 212 |
1 files changed, 212 insertions, 0 deletions
diff --git a/ast/erfa/dtf2d.c b/ast/erfa/dtf2d.c new file mode 100644 index 0000000..551d1c4 --- /dev/null +++ b/ast/erfa/dtf2d.c @@ -0,0 +1,212 @@ +#include "erfa.h" +#include <string.h> + +int eraDtf2d(const char *scale, int iy, int im, int id, + int ihr, int imn, double sec, double *d1, double *d2) +/* +** - - - - - - - - - +** e r a D t f 2 d +** - - - - - - - - - +** +** Encode date and time fields into 2-part Julian Date (or in the case +** of UTC a quasi-JD form that includes special provision for leap +** seconds). +** +** Given: +** scale char[] time scale ID (Note 1) +** iy,im,id int year, month, day in Gregorian calendar (Note 2) +** ihr,imn int hour, minute +** sec double seconds +** +** Returned: +** d1,d2 double 2-part Julian Date (Notes 3,4) +** +** Returned (function value): +** int status: +3 = both of next two +** +2 = time is after end of day (Note 5) +** +1 = dubious year (Note 6) +** 0 = OK +** -1 = bad year +** -2 = bad month +** -3 = bad day +** -4 = bad hour +** -5 = bad minute +** -6 = bad second (<0) +** +** Notes: +** +** 1) scale identifies the time scale. Only the value "UTC" (in upper +** case) is significant, and enables handling of leap seconds (see +** Note 4). +** +** 2) For calendar conventions and limitations, see eraCal2jd. +** +** 3) The sum of the results, d1+d2, is Julian Date, where normally d1 +** is the Julian Day Number and d2 is the fraction of a day. In the +** case of UTC, where the use of JD is problematical, special +** conventions apply: see the next note. +** +** 4) JD cannot unambiguously represent UTC during a leap second unless +** special measures are taken. The ERFA internal convention is that +** the quasi-JD day represents UTC days whether the length is 86399, +** 86400 or 86401 SI seconds. In the 1960-1972 era there were +** smaller jumps (in either direction) each time the linear UTC(TAI) +** expression was changed, and these "mini-leaps" are also included +** in the ERFA convention. +** +** 5) The warning status "time is after end of day" usually means that +** the sec argument is greater than 60.0. However, in a day ending +** in a leap second the limit changes to 61.0 (or 59.0 in the case +** of a negative leap second). +** +** 6) The warning status "dubious year" flags UTCs that predate the +** introduction of the time scale or that are too far in the future +** to be trusted. See eraDat for further details. +** +** 7) Only in the case of continuous and regular time scales (TAI, TT, +** TCG, TCB and TDB) is the result d1+d2 a Julian Date, strictly +** speaking. In the other cases (UT1 and UTC) the result must be +** used with circumspection; in particular the difference between +** two such results cannot be interpreted as a precise time +** interval. +** +** Called: +** eraCal2jd Gregorian calendar to JD +** eraDat delta(AT) = TAI-UTC +** eraJd2cal JD to Gregorian calendar +** +** Copyright (C) 2013-2014, NumFOCUS Foundation. +** Derived, with permission, from the SOFA library. See notes at end of file. +*/ +{ + int js, iy2, im2, id2; + double dj, w, day, seclim, dat0, dat12, dat24, dleap, time; + + +/* Today's Julian Day Number. */ + js = eraCal2jd(iy, im, id, &dj, &w); + if ( js ) return js; + dj += w; + +/* Day length and final minute length in seconds (provisional). */ + day = ERFA_DAYSEC; + seclim = 60.0; + +/* Deal with the UTC leap second case. */ + if ( ! strcmp(scale,"UTC") ) { + + /* TAI-UTC at 0h today. */ + js = eraDat(iy, im, id, 0.0, &dat0); + if ( js < 0 ) return js; + + /* TAI-UTC at 12h today (to detect drift). */ + js = eraDat(iy, im, id, 0.5, &dat12); + if ( js < 0 ) return js; + + /* TAI-UTC at 0h tomorrow (to detect jumps). */ + js = eraJd2cal ( dj, 1.5, &iy2, &im2, &id2, &w); + if ( js ) return js; + js = eraDat(iy2, im2, id2, 0.0, &dat24); + if ( js < 0 ) return js; + + /* Any sudden change in TAI-UTC between today and tomorrow. */ + dleap = dat24 - (2.0*dat12 - dat0); + + /* If leap second day, correct the day and final minute lengths. */ + day += dleap; + if ( ihr == 23 && imn == 59 ) seclim += dleap; + + /* End of UTC-specific actions. */ + } + +/* Validate the time. */ + if ( ihr >= 0 && ihr <= 23 ) { + if ( imn >= 0 && imn <= 59 ) { + if ( sec >= 0 ) { + if ( sec >= seclim ) { + js += 2; + } + } else { + js = -6; + } + } else { + js = -5; + } + } else { + js = -4; + } + if ( js < 0 ) return js; + +/* The time in days. */ + time = ( 60.0 * ( (double) ( 60 * ihr + imn ) ) + sec ) / day; + +/* Return the date and time. */ + *d1 = dj; + *d2 = time; + +/* Status. */ + return js; + +} +/*---------------------------------------------------------------------- +** +** +** Copyright (C) 2013-2014, NumFOCUS Foundation. +** All rights reserved. +** +** This library is derived, with permission, from the International +** Astronomical Union's "Standards of Fundamental Astronomy" library, +** available from http://www.iausofa.org. +** +** The ERFA version is intended to retain identical functionality to +** the SOFA library, but made distinct through different function and +** file names, as set out in the SOFA license conditions. The SOFA +** original has a role as a reference standard for the IAU and IERS, +** and consequently redistribution is permitted only in its unaltered +** state. The ERFA version is not subject to this restriction and +** therefore can be included in distributions which do not support the +** concept of "read only" software. +** +** Although the intent is to replicate the SOFA API (other than +** replacement of prefix names) and results (with the exception of +** bugs; any that are discovered will be fixed), SOFA is not +** responsible for any errors found in this version of the library. +** +** If you wish to acknowledge the SOFA heritage, please acknowledge +** that you are using a library derived from SOFA, rather than SOFA +** itself. +** +** +** TERMS AND CONDITIONS +** +** Redistribution and use in source and binary forms, with or without +** modification, are permitted provided that the following conditions +** are met: +** +** 1 Redistributions of source code must retain the above copyright +** notice, this list of conditions and the following disclaimer. +** +** 2 Redistributions in binary form must reproduce the above copyright +** notice, this list of conditions and the following disclaimer in +** the documentation and/or other materials provided with the +** distribution. +** +** 3 Neither the name of the Standards Of Fundamental Astronomy Board, +** the International Astronomical Union nor the names of its +** contributors may be used to endorse or promote products derived +** from this software without specific prior written permission. +** +** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS +** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE +** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, +** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, +** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; +** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER +** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN +** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE +** POSSIBILITY OF SUCH DAMAGE. +** +*/ |