Library interface

A simple example program

The following example program shows the typical usage of the C interface.

Other examples using the C interface can be found in the directory examples of the library sources.

#include <stdio.h>
#include "calceph.h"

int main(void)
{
 double AU;
 t_calcephbin *peph;

 peph = calceph_open("example1.dat");
 if (peph)
 {
   if (calceph_getconstant(peph, "AU", &AU))
   {
        printf("AU=%23.16E\n", AU);
   }

   calceph_close(peph);
 }
 return 0;
}

Types

type t_calcephbin

This type contains all information to access an ephemeris file.

type t_calceph_charvalue

This type is a array of characters to store the value of the constants as a string.

Constants

CALCEPH_MAX_CONSTANTNAME

This integer defines the maximum number of characters, including the trailing '\0', that the name of a constant, available from the ephemeris file, could contain.

CALCEPH_MAX_CONSTANTVALUE

This integer defines the maximum number of characters, including the trailing '\0', that the value of a constant, available from the ephemeris file, could contain if the value is stored as a string of characters.

CALCEPH_VERSION_MAJOR

This integer constant defines the major revision of this library. It can be used to distinguish different releases of this library.

CALCEPH_VERSION_MINOR

This integer constant defines the minor revision of this library. It can be used to distinguish different releases of this library.

CALCEPH_VERSION_PATCH

This integer constant defines the patch level revision of this library. It can be used to distinguish different releases of this library.

#if   (CALCEPH_VERSION_MAJOR>=2)
  ||  (CALCEPH_VERSION_MAJOR>=3 && CALCEPH_VERSION_MINOR>=2)
...
#endif
CALCEPH_VERSION_STRING

This C null-terminated string constant is the version of the library, which can be compared to the result of calceph_getversion to check at run time if the header file and library used match:

char version[CALCEPH_MAX_CONSTANTNAME];
calceph_getversion_str(version);
if (strcmp (version, CALCEPH_VERSION_STRING)!=0)
fprintf (stderr, "Warning: header and library do not match\n");

Note: Obtaining different strings is not necessarily an error, as in general, a program compiled with some old CALCEPH version can be dynamically linked with a newer CALCEPH library version (if allowed by the operating system).

CALCEPH_ASTEROID

This integer defines the offset value for the asteroids that must be used as target or center for the computation functions, such as calceph_compute().

The following constants specify in which units are expressed the output of the computation functions, such as calceph_compute_unit() :

CALCEPH_UNIT_AU

This integer defines that the unit of the positions and velocities is expressed in astronomical unit.

CALCEPH_UNIT_KM

This integer defines that the unit of the positions and velocities is expressed in kilometer.

CALCEPH_UNIT_DAY

This integer defines that the unit of the velocities or the quantity TT-TDB or TCG-TCB is expressed in day (one day=86400 seconds).

CALCEPH_UNIT_SEC

This integer defines that the unit of the velocities or the quantity TT-TDB or TCG-TCB is expressed in second.

CALCEPH_UNIT_RAD

This integer defines that the unit of the angles is expressed in radian.

CALCEPH_OUTPUT_EULERANGLES

This integer defines that the output array contains the euler angles.

CALCEPH_OUTPUT_NUTATIONANGLES

This integer defines that the output array contains the nutation angles.

CALCEPH_USE_NAIFID

This integer defines that the NAIF identification numbers are used as target or center for the computation functions, such as calceph_compute_unit().