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authorWilliam Joye <wjoye@cfa.harvard.edu>2019-05-10 16:24:30 (GMT)
committerWilliam Joye <wjoye@cfa.harvard.edu>2019-05-10 16:24:30 (GMT)
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+#include "erfa.h"
+
+int eraUtctai(double utc1, double utc2, double *tai1, double *tai2)
+/*
+** - - - - - - - - - -
+** e r a U t c t a i
+** - - - - - - - - - -
+**
+** Time scale transformation: Coordinated Universal Time, UTC, to
+** International Atomic Time, TAI.
+**
+** Given:
+** utc1,utc2 double UTC as a 2-part quasi Julian Date (Notes 1-4)
+**
+** Returned:
+** tai1,tai2 double TAI as a 2-part Julian Date (Note 5)
+**
+** Returned (function value):
+** int status: +1 = dubious year (Note 3)
+** 0 = OK
+** -1 = unacceptable date
+**
+** Notes:
+**
+** 1) utc1+utc2 is quasi Julian Date (see Note 2), apportioned in any
+** convenient way between the two arguments, for example where utc1
+** is the Julian Day Number and utc2 is the fraction of a day.
+**
+** 2) JD cannot unambiguously represent UTC during a leap second unless
+** special measures are taken. The convention in the present
+** function is that the 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.
+**
+** 3) 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.
+**
+** 4) The function eraDtf2d converts from calendar date and time of day
+** into 2-part Julian Date, and in the case of UTC implements the
+** leap-second-ambiguity convention described above.
+**
+** 5) The returned TAI1,TAI2 are such that their sum is the TAI Julian
+** Date.
+**
+** Called:
+** eraJd2cal JD to Gregorian calendar
+** eraDat delta(AT) = TAI-UTC
+** eraCal2jd Gregorian calendar to JD
+**
+** References:
+**
+** McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
+** IERS Technical Note No. 32, BKG (2004)
+**
+** Explanatory Supplement to the Astronomical Almanac,
+** P. Kenneth Seidelmann (ed), University Science Books (1992)
+**
+** Copyright (C) 2013-2016, NumFOCUS Foundation.
+** Derived, with permission, from the SOFA library. See notes at end of file.
+*/
+{
+ int big1;
+ int iy, im, id, j, iyt, imt, idt;
+ double u1, u2, fd, dat0, dat12, w, dat24, dlod, dleap, z1, z2, a2;
+
+
+/* Put the two parts of the UTC into big-first order. */
+ big1 = ( utc1 >= utc2 );
+ if ( big1 ) {
+ u1 = utc1;
+ u2 = utc2;
+ } else {
+ u1 = utc2;
+ u2 = utc1;
+ }
+
+/* Get TAI-UTC at 0h today. */
+ j = eraJd2cal(u1, u2, &iy, &im, &id, &fd);
+ if ( j ) return j;
+ j = eraDat(iy, im, id, 0.0, &dat0);
+ if ( j < 0 ) return j;
+
+/* Get TAI-UTC at 12h today (to detect drift). */
+ j = eraDat(iy, im, id, 0.5, &dat12);
+ if ( j < 0 ) return j;
+
+/* Get TAI-UTC at 0h tomorrow (to detect jumps). */
+ j = eraJd2cal(u1+1.5, u2-fd, &iyt, &imt, &idt, &w);
+ if ( j ) return j;
+ j = eraDat(iyt, imt, idt, 0.0, &dat24);
+ if ( j < 0 ) return j;
+
+/* Separate TAI-UTC change into per-day (DLOD) and any jump (DLEAP). */
+ dlod = 2.0 * (dat12 - dat0);
+ dleap = dat24 - (dat0 + dlod);
+
+/* Remove any scaling applied to spread leap into preceding day. */
+ fd *= (ERFA_DAYSEC+dleap)/ERFA_DAYSEC;
+
+/* Scale from (pre-1972) UTC seconds to SI seconds. */
+ fd *= (ERFA_DAYSEC+dlod)/ERFA_DAYSEC;
+
+/* Today's calendar date to 2-part JD. */
+ if ( eraCal2jd(iy, im, id, &z1, &z2) ) return -1;
+
+/* Assemble the TAI result, preserving the UTC split and order. */
+ a2 = z1 - u1;
+ a2 += z2;
+ a2 += fd + dat0/ERFA_DAYSEC;
+ if ( big1 ) {
+ *tai1 = u1;
+ *tai2 = a2;
+ } else {
+ *tai1 = a2;
+ *tai2 = u1;
+ }
+
+/* Status. */
+ return j;
+
+}
+/*----------------------------------------------------------------------
+**
+**
+** Copyright (C) 2013-2016, 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.
+**
+*/