dayofyear.c

来自「天文算法」· C语言 代码 · 共 101 行

/**************************************************************************
  AstronomicalAlgorithms

  A portable ANSI C implementation of some of the algorithms published in

        Astronomical Algorithms
        by Jean Meeus
        2nd edition (December 1998)
        Willmann-Bell
        ISBN: 0943396638

  by Christophe DAVID ([e-mail])

  You may use parts of this source code as long as

       - you mention clearly that its latest version can be obtained
         free of charge at

         http://www.christophedavid.org/

       AND

      - you send me a free copy of whatever you make using this code.

     Comments and suggestions welcome.

**************************************************************************/

/*!
@file
@brief       calculates the day of year for a given date
@author      Christophe DAVID \n
             [e-mail] \n
             http://www.christophedavid.org
@since       01/07/1999
@version     1.0
@date        05/04/2001
@bug         no known bug

@param double * DayOfYear
@param double   year
@param double   month
@param double   day

@return
- 0 : completed successfully
- 1 : error in parameter 1
- 2 : error in parameter 2
- 3 : error in parameter 3
- 4 : error in parameter 4

@if logger
@image html http://www.mot.be/cgi-bin/logger.cgi?DayOfYear.c
@endif
*/

/* see page 65 */

#ifdef ASTROALGO
   #include <math.h>
   #include <stdio.h>
   #include "AstroAlgo.h"

   __declspec(dllexport) short __stdcall
#else
   short
#endif

ShDayOfYear(short *pshDOY, double doY, double doM, double doD)
   {
   short  shReturnValue = (short)  0;

   if (pshDOY == NULL)
      {
      shReturnValue = (short) 1;
      }

   else
      {
      short shIsLeap = (short) 0;

      *pshDOY = (short) -1;
      shReturnValue = ShIsLeapYear(&shIsLeap, (short) doY,
                                  (short) (doY < 1582 ? JULIAN : GREGORIAN));

      if (shReturnValue == 0)
         {
         *pshDOY = (short) (  floor((((double) 275) * doM) / (double)  9)
                            - (  (double) (shIsLeap == 1 ? 1 : 2)
                               *  floor((((double)   9) + doM) / (double) 12)
                              )
                            + doD
                            - (double) 30
                           );
         }
      }

   return shReturnValue;
   }