source: trunk/FACT++/erfa/src/d2tf.c@ 19098

Last change on this file since 19098 was 18921, checked in by tbretz, 7 years ago
Updated to ERFA 1.4.0
File size: 5.7 KB
Line 
1#include "erfa.h"
2
3void eraD2tf(int ndp, double days, char *sign, int ihmsf[4])
4/*
5** - - - - - - - -
6** e r a D 2 t f
7** - - - - - - - -
8**
9** Decompose days to hours, minutes, seconds, fraction.
10**
11** Given:
12** ndp int resolution (Note 1)
13** days double interval in days
14**
15** Returned:
16** sign char '+' or '-'
17** ihmsf int[4] hours, minutes, seconds, fraction
18**
19** Notes:
20**
21** 1) The argument ndp is interpreted as follows:
22**
23** ndp resolution
24** : ...0000 00 00
25** -7 1000 00 00
26** -6 100 00 00
27** -5 10 00 00
28** -4 1 00 00
29** -3 0 10 00
30** -2 0 01 00
31** -1 0 00 10
32** 0 0 00 01
33** 1 0 00 00.1
34** 2 0 00 00.01
35** 3 0 00 00.001
36** : 0 00 00.000...
37**
38** 2) The largest positive useful value for ndp is determined by the
39** size of days, the format of double on the target platform, and
40** the risk of overflowing ihmsf[3]. On a typical platform, for
41** days up to 1.0, the available floating-point precision might
42** correspond to ndp=12. However, the practical limit is typically
43** ndp=9, set by the capacity of a 32-bit int, or ndp=4 if int is
44** only 16 bits.
45**
46** 3) The absolute value of days may exceed 1.0. In cases where it
47** does not, it is up to the caller to test for and handle the
48** case where days is very nearly 1.0 and rounds up to 24 hours,
49** by testing for ihmsf[0]=24 and setting ihmsf[0-3] to zero.
50**
51** Copyright (C) 2013-2017, NumFOCUS Foundation.
52** Derived, with permission, from the SOFA library. See notes at end of file.
53*/
54{
55 int nrs, n;
56 double rs, rm, rh, a, w, ah, am, as, af;
57
58
59/* Handle sign. */
60 *sign = (char) ( ( days >= 0.0 ) ? '+' : '-' );
61
62/* Interval in seconds. */
63 a = ERFA_DAYSEC * fabs(days);
64
65/* Pre-round if resolution coarser than 1s (then pretend ndp=1). */
66 if (ndp < 0) {
67 nrs = 1;
68 for (n = 1; n <= -ndp; n++) {
69 nrs *= (n == 2 || n == 4) ? 6 : 10;
70 }
71 rs = (double) nrs;
72 w = a / rs;
73 a = rs * ERFA_DNINT(w);
74 }
75
76/* Express the unit of each field in resolution units. */
77 nrs = 1;
78 for (n = 1; n <= ndp; n++) {
79 nrs *= 10;
80 }
81 rs = (double) nrs;
82 rm = rs * 60.0;
83 rh = rm * 60.0;
84
85/* Round the interval and express in resolution units. */
86 a = ERFA_DNINT(rs * a);
87
88/* Break into fields. */
89 ah = a / rh;
90 ah = ERFA_DINT(ah);
91 a -= ah * rh;
92 am = a / rm;
93 am = ERFA_DINT(am);
94 a -= am * rm;
95 as = a / rs;
96 as = ERFA_DINT(as);
97 af = a - as * rs;
98
99/* Return results. */
100 ihmsf[0] = (int) ah;
101 ihmsf[1] = (int) am;
102 ihmsf[2] = (int) as;
103 ihmsf[3] = (int) af;
104
105 return;
106
107}
108/*----------------------------------------------------------------------
109**
110**
111** Copyright (C) 2013-2017, NumFOCUS Foundation.
112** All rights reserved.
113**
114** This library is derived, with permission, from the International
115** Astronomical Union's "Standards of Fundamental Astronomy" library,
116** available from http://www.iausofa.org.
117**
118** The ERFA version is intended to retain identical functionality to
119** the SOFA library, but made distinct through different function and
120** file names, as set out in the SOFA license conditions. The SOFA
121** original has a role as a reference standard for the IAU and IERS,
122** and consequently redistribution is permitted only in its unaltered
123** state. The ERFA version is not subject to this restriction and
124** therefore can be included in distributions which do not support the
125** concept of "read only" software.
126**
127** Although the intent is to replicate the SOFA API (other than
128** replacement of prefix names) and results (with the exception of
129** bugs; any that are discovered will be fixed), SOFA is not
130** responsible for any errors found in this version of the library.
131**
132** If you wish to acknowledge the SOFA heritage, please acknowledge
133** that you are using a library derived from SOFA, rather than SOFA
134** itself.
135**
136**
137** TERMS AND CONDITIONS
138**
139** Redistribution and use in source and binary forms, with or without
140** modification, are permitted provided that the following conditions
141** are met:
142**
143** 1 Redistributions of source code must retain the above copyright
144** notice, this list of conditions and the following disclaimer.
145**
146** 2 Redistributions in binary form must reproduce the above copyright
147** notice, this list of conditions and the following disclaimer in
148** the documentation and/or other materials provided with the
149** distribution.
150**
151** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
152** the International Astronomical Union nor the names of its
153** contributors may be used to endorse or promote products derived
154** from this software without specific prior written permission.
155**
156** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
157** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
158** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
159** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
160** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
161** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
162** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
163** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
164** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
165** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
166** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
167** POSSIBILITY OF SUCH DAMAGE.
168**
169*/
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