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#include "erfa.h"
int eraTaiutc(double tai1, double tai2, double *utc1, double *utc2)
/*
** - - - - - - - - - -
** e r a T a i u t c
** - - - - - - - - - -
**
** Time scale transformation: International Atomic Time, TAI, to
** Coordinated Universal Time, UTC.
**
** Given:
** tai1,tai2 double TAI as a 2-part Julian Date (Note 1)
**
** Returned:
** utc1,utc2 double UTC as a 2-part quasi Julian Date (Notes 1-3)
**
** Returned (function value):
** int status: +1 = dubious year (Note 4)
** 0 = OK
** -1 = unacceptable date
**
** Notes:
**
** 1) tai1+tai2 is Julian Date, apportioned in any convenient way
** between the two arguments, for example where tai1 is the Julian
** Day Number and tai2 is the fraction of a day. The returned utc1
** and utc2 form an analogous pair, except that a special convention
** is used, to deal with the problem of leap seconds - see the next
** note.
**
** 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 function eraD2dtf can be used to transform the UTC quasi-JD
** into calendar date and clock time, including UTC leap second
** handling.
**
** 4) 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.
**
** Called:
** eraUtctai UTC to TAI
**
** 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 i, j;
double a1, a2, u1, u2, g1, g2;
/* Put the two parts of the TAI into big-first order. */
big1 = ( tai1 >= tai2 );
if ( big1 ) {
a1 = tai1;
a2 = tai2;
} else {
a1 = tai2;
a2 = tai1;
}
/* Initial guess for UTC. */
u1 = a1;
u2 = a2;
/* Iterate (though in most cases just once is enough). */
for ( i = 0; i < 3; i++ ) {
/* Guessed UTC to TAI. */
j = eraUtctai(u1, u2, &g1, &g2);
if ( j < 0 ) return j;
/* Adjust guessed UTC. */
u2 += a1 - g1;
u2 += a2 - g2;
}
/* Return the UTC result, preserving the TAI order. */
if ( big1 ) {
*utc1 = u1;
*utc2 = u2;
} else {
*utc1 = u2;
*utc2 = 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.
**
*/
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