source: branches/FACT++_part_filenames/erfa/src/jdcalf.c@ 18795

Last change on this file since 18795 was 18711, checked in by tbretz, 8 years ago
Updated to ERFA 1.3.0 (no relevant code change except the leap second at the beginning of 2017)
File size: 5.8 KB
Line 
1#include "erfa.h"
2
3int eraJdcalf(int ndp, double dj1, double dj2, int iymdf[4])
4/*
5** - - - - - - - - - -
6** e r a J d c a l f
7** - - - - - - - - - -
8**
9** Julian Date to Gregorian Calendar, expressed in a form convenient
10** for formatting messages: rounded to a specified precision.
11**
12** Given:
13** ndp int number of decimal places of days in fraction
14** dj1,dj2 double dj1+dj2 = Julian Date (Note 1)
15**
16** Returned:
17** iymdf int[4] year, month, day, fraction in Gregorian
18** calendar
19**
20** Returned (function value):
21** int status:
22** -1 = date out of range
23** 0 = OK
24** +1 = NDP not 0-9 (interpreted as 0)
25**
26** Notes:
27**
28** 1) The Julian Date is apportioned in any convenient way between
29** the arguments dj1 and dj2. For example, JD=2450123.7 could
30** be expressed in any of these ways, among others:
31**
32** dj1 dj2
33**
34** 2450123.7 0.0 (JD method)
35** 2451545.0 -1421.3 (J2000 method)
36** 2400000.5 50123.2 (MJD method)
37** 2450123.5 0.2 (date & time method)
38**
39** 2) In early eras the conversion is from the "Proleptic Gregorian
40** Calendar"; no account is taken of the date(s) of adoption of
41** the Gregorian Calendar, nor is the AD/BC numbering convention
42** observed.
43**
44** 3) Refer to the function eraJd2cal.
45**
46** 4) NDP should be 4 or less if internal overflows are to be
47** avoided on machines which use 16-bit integers.
48**
49** Called:
50** eraJd2cal JD to Gregorian calendar
51**
52** Reference:
53**
54** Explanatory Supplement to the Astronomical Almanac,
55** P. Kenneth Seidelmann (ed), University Science Books (1992),
56** Section 12.92 (p604).
57**
58** Copyright (C) 2013-2016, NumFOCUS Foundation.
59** Derived, with permission, from the SOFA library. See notes at end of file.
60*/
61{
62 int j, js;
63 double denom, d1, d2, f1, f2, f;
64
65
66/* Denominator of fraction (e.g. 100 for 2 decimal places). */
67 if ((ndp >= 0) && (ndp <= 9)) {
68 j = 0;
69 denom = pow(10.0, ndp);
70 } else {
71 j = 1;
72 denom = 1.0;
73 }
74
75/* Copy the date, big then small, and realign to midnight. */
76 if (dj1 >= dj2) {
77 d1 = dj1;
78 d2 = dj2;
79 } else {
80 d1 = dj2;
81 d2 = dj1;
82 }
83 d2 -= 0.5;
84
85/* Separate days and fractions. */
86 f1 = fmod(d1, 1.0);
87 f2 = fmod(d2, 1.0);
88 d1 = floor(d1 - f1);
89 d2 = floor(d2 - f2);
90
91/* Round the total fraction to the specified number of places. */
92 f = floor((f1+f2)*denom + 0.5) / denom;
93
94/* Re-assemble the rounded date and re-align to noon. */
95 d2 += f + 0.5;
96
97/* Convert to Gregorian calendar. */
98 js = eraJd2cal(d1, d2, &iymdf[0], &iymdf[1], &iymdf[2], &f);
99 if (js == 0) {
100 iymdf[3] = (int) (f * denom);
101 } else {
102 j = js;
103 }
104
105/* Return the status. */
106 return j;
107
108}
109/*----------------------------------------------------------------------
110**
111**
112** Copyright (C) 2013-2016, NumFOCUS Foundation.
113** All rights reserved.
114**
115** This library is derived, with permission, from the International
116** Astronomical Union's "Standards of Fundamental Astronomy" library,
117** available from http://www.iausofa.org.
118**
119** The ERFA version is intended to retain identical functionality to
120** the SOFA library, but made distinct through different function and
121** file names, as set out in the SOFA license conditions. The SOFA
122** original has a role as a reference standard for the IAU and IERS,
123** and consequently redistribution is permitted only in its unaltered
124** state. The ERFA version is not subject to this restriction and
125** therefore can be included in distributions which do not support the
126** concept of "read only" software.
127**
128** Although the intent is to replicate the SOFA API (other than
129** replacement of prefix names) and results (with the exception of
130** bugs; any that are discovered will be fixed), SOFA is not
131** responsible for any errors found in this version of the library.
132**
133** If you wish to acknowledge the SOFA heritage, please acknowledge
134** that you are using a library derived from SOFA, rather than SOFA
135** itself.
136**
137**
138** TERMS AND CONDITIONS
139**
140** Redistribution and use in source and binary forms, with or without
141** modification, are permitted provided that the following conditions
142** are met:
143**
144** 1 Redistributions of source code must retain the above copyright
145** notice, this list of conditions and the following disclaimer.
146**
147** 2 Redistributions in binary form must reproduce the above copyright
148** notice, this list of conditions and the following disclaimer in
149** the documentation and/or other materials provided with the
150** distribution.
151**
152** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
153** the International Astronomical Union nor the names of its
154** contributors may be used to endorse or promote products derived
155** from this software without specific prior written permission.
156**
157** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
158** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
159** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
160** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
161** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
162** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
163** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
164** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
165** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
166** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
167** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
168** POSSIBILITY OF SUCH DAMAGE.
169**
170*/
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