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#include "sofa.h"
#include <float.h>
int iauJd2cal(double dj1, double dj2,
int *iy, int *im, int *id, double *fd)
/*
** - - - - - - - - - -
** i a u J d 2 c a l
** - - - - - - - - - -
**
** Julian Date to Gregorian year, month, day, and fraction of a day.
**
** This function is part of the International Astronomical Union's
** SOFA (Standards Of Fundamental Astronomy) software collection.
**
** Status: support function.
**
** Given:
** dj1,dj2 double Julian Date (Notes 1, 2)
**
** Returned (arguments):
** iy int year
** im int month
** id int day
** fd double fraction of day
**
** Returned (function value):
** int status:
** 0 = OK
** -1 = unacceptable date (Note 1)
**
** Notes:
**
** 1) The earliest valid date is -68569.5 (-4900 March 1). The
** largest value accepted is 1e9.
**
** 2) The Julian Date is apportioned in any convenient way between
** the arguments dj1 and dj2. For example, JD=2450123.7 could
** be expressed in any of these ways, among others:
**
** dj1 dj2
**
** 2450123.7 0.0 (JD method)
** 2451545.0 -1421.3 (J2000 method)
** 2400000.5 50123.2 (MJD method)
** 2450123.5 0.2 (date & time method)
**
** Separating integer and fraction uses the "compensated summation"
** algorithm of Kahan-Neumaier to preserve as much precision as
** possible irrespective of the jd1+jd2 apportionment.
**
** 3) In early eras the conversion is from the "proleptic Gregorian
** calendar"; no account is taken of the date(s) of adoption of
** the Gregorian calendar, nor is the AD/BC numbering convention
** observed.
**
** References:
**
** Explanatory Supplement to the Astronomical Almanac,
** P. Kenneth Seidelmann (ed), University Science Books (1992),
** Section 12.92 (p604).
**
** Klein, A., A Generalized Kahan-Babuska-Summation-Algorithm.
** Computing 76, 279-293 (2006), Section 3.
**
** This revision: 2020 June 24
**
** SOFA release 2020-07-21
**
** Copyright (C) 2020 IAU SOFA Board. See notes at end.
*/
{
/* Minimum and maximum allowed JD */
const double DJMIN = -68569.5;
const double DJMAX = 1e9;
long jd, i, l, n, k;
double dj, f1, f2, d, s, cs, v[2], x, t, f;
/* Verify date is acceptable. */
dj = dj1 + dj2;
if (dj < DJMIN || dj > DJMAX) return -1;
/* Separate day and fraction (where -0.5 <= fraction < 0.5). */
d = dnint(dj1);
f1 = dj1 - d;
jd = (long) d;
d = dnint(dj2);
f2 = dj2 - d;
jd += (long) d;
/* Compute f1+f2+0.5 using compensated summation (Klein 2006). */
s = 0.5;
cs = 0.0;
v[0] = f1;
v[1] = f2;
for ( i = 0; i < 2; i++ ) {
x = v[i];
t = s + x;
cs += fabs(s) >= fabs(x) ? (s-t) + x : (x-t) + s;
s = t;
if ( s >= 1.0 ) {
jd++;
s -= 1.0;
}
}
f = s + cs;
cs = f - s;
/* Deal with negative f. */
if ( f < 0.0 ) {
/* Compensated summation: assume that |s| <= 1.0. */
f = s + 1.0;
cs += (1.0-f) + s;
s = f;
f = s + cs;
cs = f - s;
jd--;
}
/* Deal with f that is 1.0 or more (when rounded to double). */
if ( (f-1.0) >= -DBL_EPSILON/4.0 ) {
/* Compensated summation: assume that |s| <= 1.0. */
t = s - 1.0;
cs += (s-t) - 1.0;
s = t;
f = s + cs;
if ( -DBL_EPSILON/2.0 < f ) {
jd++;
f = gmax(f, 0.0);
}
}
/* Express day in Gregorian calendar. */
l = jd + 68569L;
n = (4L * l) / 146097L;
l -= (146097L * n + 3L) / 4L;
i = (4000L * (l + 1L)) / 1461001L;
l -= (1461L * i) / 4L - 31L;
k = (80L * l) / 2447L;
*id = (int) (l - (2447L * k) / 80L);
l = k / 11L;
*im = (int) (k + 2L - 12L * l);
*iy = (int) (100L * (n - 49L) + i + l);
*fd = f;
return 0;
/*----------------------------------------------------------------------
**
** Copyright (C) 2020
** Standards Of Fundamental Astronomy Board
** of the International Astronomical Union.
**
** =====================
** SOFA Software License
** =====================
**
** NOTICE TO USER:
**
** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
** CONDITIONS WHICH APPLY TO ITS USE.
**
** 1. The Software is owned by the IAU SOFA Board ("SOFA").
**
** 2. Permission is granted to anyone to use the SOFA software for any
** purpose, including commercial applications, free of charge and
** without payment of royalties, subject to the conditions and
** restrictions listed below.
**
** 3. You (the user) may copy and distribute SOFA source code to others,
** and use and adapt its code and algorithms in your own software,
** on a world-wide, royalty-free basis. That portion of your
** distribution that does not consist of intact and unchanged copies
** of SOFA source code files is a "derived work" that must comply
** with the following requirements:
**
** a) Your work shall be marked or carry a statement that it
** (i) uses routines and computations derived by you from
** software provided by SOFA under license to you; and
** (ii) does not itself constitute software provided by and/or
** endorsed by SOFA.
**
** b) The source code of your derived work must contain descriptions
** of how the derived work is based upon, contains and/or differs
** from the original SOFA software.
**
** c) The names of all routines in your derived work shall not
** include the prefix "iau" or "sofa" or trivial modifications
** thereof such as changes of case.
**
** d) The origin of the SOFA components of your derived work must
** not be misrepresented; you must not claim that you wrote the
** original software, nor file a patent application for SOFA
** software or algorithms embedded in the SOFA software.
**
** e) These requirements must be reproduced intact in any source
** distribution and shall apply to anyone to whom you have
** granted a further right to modify the source code of your
** derived work.
**
** Note that, as originally distributed, the SOFA software is
** intended to be a definitive implementation of the IAU standards,
** and consequently third-party modifications are discouraged. All
** variations, no matter how minor, must be explicitly marked as
** such, as explained above.
**
** 4. You shall not cause the SOFA software to be brought into
** disrepute, either by misuse, or use for inappropriate tasks, or
** by inappropriate modification.
**
** 5. The SOFA software is provided "as is" and SOFA makes no warranty
** as to its use or performance. SOFA does not and cannot warrant
** the performance or results which the user may obtain by using the
** SOFA software. SOFA makes no warranties, express or implied, as
** to non-infringement of third party rights, merchantability, or
** fitness for any particular purpose. In no event will SOFA be
** liable to the user for any consequential, incidental, or special
** damages, including any lost profits or lost savings, even if a
** SOFA representative has been advised of such damages, or for any
** claim by any third party.
**
** 6. The provision of any version of the SOFA software under the terms
** and conditions specified herein does not imply that future
** versions will also be made available under the same terms and
** conditions.
*
** In any published work or commercial product which uses the SOFA
** software directly, acknowledgement (see www.iausofa.org) is
** appreciated.
**
** Correspondence concerning SOFA software should be addressed as
** follows:
**
** By email: sofa@ukho.gov.uk
** By post: IAU SOFA Center
** HM Nautical Almanac Office
** UK Hydrographic Office
** Admiralty Way, Taunton
** Somerset, TA1 2DN
** United Kingdom
**
**--------------------------------------------------------------------*/
}