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Diffstat (limited to 'ast/erfa/d2tf.c')
| -rw-r--r-- | ast/erfa/d2tf.c | 169 |
1 files changed, 169 insertions, 0 deletions
diff --git a/ast/erfa/d2tf.c b/ast/erfa/d2tf.c new file mode 100644 index 0000000..3608f7f --- /dev/null +++ b/ast/erfa/d2tf.c @@ -0,0 +1,169 @@ +#include "erfa.h" + +void eraD2tf(int ndp, double days, char *sign, int ihmsf[4]) +/* +** - - - - - - - - +** e r a D 2 t f +** - - - - - - - - +** +** Decompose days to hours, minutes, seconds, fraction. +** +** Given: +** ndp int resolution (Note 1) +** days double interval in days +** +** Returned: +** sign char '+' or '-' +** ihmsf int[4] hours, minutes, seconds, fraction +** +** Notes: +** +** 1) The argument ndp is interpreted as follows: +** +** ndp resolution +** : ...0000 00 00 +** -7 1000 00 00 +** -6 100 00 00 +** -5 10 00 00 +** -4 1 00 00 +** -3 0 10 00 +** -2 0 01 00 +** -1 0 00 10 +** 0 0 00 01 +** 1 0 00 00.1 +** 2 0 00 00.01 +** 3 0 00 00.001 +** : 0 00 00.000... +** +** 2) The largest positive useful value for ndp is determined by the +** size of days, the format of double on the target platform, and +** the risk of overflowing ihmsf[3]. On a typical platform, for +** days up to 1.0, the available floating-point precision might +** correspond to ndp=12. However, the practical limit is typically +** ndp=9, set by the capacity of a 32-bit int, or ndp=4 if int is +** only 16 bits. +** +** 3) The absolute value of days may exceed 1.0. In cases where it +** does not, it is up to the caller to test for and handle the +** case where days is very nearly 1.0 and rounds up to 24 hours, +** by testing for ihmsf[0]=24 and setting ihmsf[0-3] to zero. +** +** Copyright (C) 2013-2016, NumFOCUS Foundation. +** Derived, with permission, from the SOFA library. See notes at end of file. +*/ +{ + int nrs, n; + double rs, rm, rh, a, w, ah, am, as, af; + + +/* Handle sign. */ + *sign = (char) ( ( days >= 0.0 ) ? '+' : '-' ); + +/* Interval in seconds. */ + a = ERFA_DAYSEC * fabs(days); + +/* Pre-round if resolution coarser than 1s (then pretend ndp=1). */ + if (ndp < 0) { + nrs = 1; + for (n = 1; n <= -ndp; n++) { + nrs *= (n == 2 || n == 4) ? 6 : 10; + } + rs = (double) nrs; + w = a / rs; + a = rs * ERFA_DNINT(w); + } + +/* Express the unit of each field in resolution units. */ + nrs = 1; + for (n = 1; n <= ndp; n++) { + nrs *= 10; + } + rs = (double) nrs; + rm = rs * 60.0; + rh = rm * 60.0; + +/* Round the interval and express in resolution units. */ + a = ERFA_DNINT(rs * a); + +/* Break into fields. */ + ah = a / rh; + ah = ERFA_DINT(ah); + a -= ah * rh; + am = a / rm; + am = ERFA_DINT(am); + a -= am * rm; + as = a / rs; + as = ERFA_DINT(as); + af = a - as * rs; + +/* Return results. */ + ihmsf[0] = (int) ah; + ihmsf[1] = (int) am; + ihmsf[2] = (int) as; + ihmsf[3] = (int) af; + + return; + +} +/*---------------------------------------------------------------------- +** +** +** 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. +** +*/ |