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Example udunits-2 compatible code

These example programs can be downloaded along with the main CalCalcs code here.

This first example shows how to use the utCalendar2_cal and utInvCalendar2_cal calls. Note that you do not have to initialize a CalCalcs calendar to use these calls; the only thing passed is the name of the calendar to use (i.e., "Standard", "Gregorian", "Juilan", etc.). This simplifies the interface for these two routines and makes them nearly drop-in replacements for the old utCalendar and utInvCalendar routines found in version 1 of the udunits library.

#include <stdio.h>
#include <stdlib.h>

#include <udunits2.h>
#include "calcalcs.h"
#include "utCalendar2_cal.h"

/* Exercise the udunits calls */

int main( int argc, char *argv[] )
{
    static char *units = "seconds since 2010-01-06 09:20";
    static char *calendar = "Standard";

    ut_system *u_system;
    ut_unit *u_1;
    double tval, tval_inv, sec;
    int ierr, yr, mo, day, hr, min;

    /* Initialize the udunits-2 library */
    if( (u_system = ut_read_xml( NULL )) == NULL ) {
        fprintf( stderr, "Error initializing udunits-2 unit system\n" );
        exit(-1);
        }

    /* Parse the units strings */
    if( (u_1 = ut_parse( u_system, units, UT_ASCII )) == NULL ) {
        fprintf( stderr, "Error parsing units string \"%s\"\n", units );
        exit(-1);
        }

    /* Make the Calendar calls */
    tval = 86460.0; /* in seconds, this is 1 day and 1 minute */

    if( (ierr = utCalendar2_cal( tval, u_1, &yr, &mo, &day, &hr, &min, &sec, calendar )) != 0 ) {
        fprintf( stderr, "Error on utCalendar2_cal call: %s\n", ccs_err_str(ierr) );
        exit(-1);
        }
    printf( "%lf %s in the %s calendar equals date %04d-%02d-%02d %02d:%02d:%06.3lf\n",
        tval, units, calendar, yr, mo, day, hr, min, sec );

    /* For a test, convert back from the date to a value and see if it matches */
    if( (ierr = utInvCalendar2_cal( yr, mo, day, hr, min, sec, u_1, &tval_inv, calendar )) != 0 ) {
        fprintf( stderr, "Error on utCalendar2_cal call: %s\n", ccs_err_str(ierr) );
        exit(-1);
        }
    printf( "Test: %04d-%02d-%02d %02d:%02d:%06.3lf is %lf %s in the %s calendar\n",
        yr, mo, day, hr, min, sec, tval_inv, units, calendar );

    return(0);
}

Example CalCalcs code

This second example shows how to use the Calcalcs library proper. Note that you do not have to link to the udunits-2 library to use this code. This example program can be downloaded along with the main CalCalcs code here.

#include <stdio.h>
#include <stdlib.h>

#include "calcalcs.h"

/*=======================================================================*/
void do_tests( const char *calendar_name, int year, int month, int day )
{
    calcalcs_cal    *cal;
    int        ierr, jday, leap, tyear, tmonth, tday, doy, days_since;

    /* Initialize the calendar */
    if( (cal = ccs_init_calendar( calendar_name )) == NULL ) {
        fprintf( stderr, "Error trying to initialize calendar %s\n",
            calendar_name );
        exit(-1);
        }

    /* Is the passed year a leap year? */
    if( (ierr = ccs_isleap( cal, year, &leap )) != 0 )
        printf( "Determining whether %d is a leap year in the %s calendar returned an error: %s\n",
            year, calendar_name, ccs_err_str(ierr) );
    else
        printf( "Year %d %s a leap year in the %s calendar\n",
            year, ((leap==1)?"IS":"is NOT"), calendar_name );

    /* Convert the passed Y/M/D date to a Julian day number */
    if( (ierr = ccs_date2jday( cal, year, month, day, &jday )) != 0 )
        printf( "Turning %04d-%02d-%02d into a Julian day returned an error: %s\n",
            year, month, day, ccs_err_str(ierr) );
    else
        printf( "%04d-%02d-%02d in the %s calendar is Julian day %d\n",
            year, month, day, calendar_name, jday );

    /* Convert the julian day we just calcalculated back into a date, it should match! */
    if( (ierr = ccs_jday2date( cal, jday, &tyear, &tmonth, &tday )) != 0 )
        printf( "Turning Julian day %d into a date returned an error: %s\n",
            jday, ccs_err_str(ierr) );
    else
        printf( "Julian day %d is date %04d-%02d-%02d in the %s calendar\n",
            jday, tyear, tmonth, tday, calendar_name );

    /* Get the day number of the year */
    if( (ierr = ccs_date2doy( cal, year, month, day, &doy )) != 0 )
        printf( "Turning %04d-%02d-%02d into a day-of-year returned an error: %s\n",
            year, month, day, ccs_err_str(ierr) );
    else
        printf( "%04d-%02d-%02d in the %s calendar is day-of-year number %d\n",
            year, month, day, calendar_name, doy );

    /* Convert the day-of-year we just calculated back into a date, it should match */
    if( (ierr = ccs_doy2date( cal, year, doy, &tmonth, &tday )) != 0 )
        printf( "Turning day %d of year %d into a date in the %s calendar returned an error: %s\n",
            doy, year, calendar_name, ccs_err_str(ierr) );
    else
        printf( "day-of-year %d of year %d is date %04d-%02d-%02d in the %s calendar\n",
            doy, year, year, tmonth, tday, calendar_name );

    /* Do a couple "days since" calls */
    days_since = 5;
    if( (ierr = ccs_dayssince( cal, year, month, day, days_since, cal, &tyear, &tmonth, &tday )) != 0 )
        printf( "Calculating %d days since %04d-%02d-%02d in the %s calendar gave error %s\n",
            days_since, year, month, day, calendar_name, ccs_err_str(ierr));
    else
        printf( "%d days since %04d-%02d-%02d in the %s calendar is %04d-%02d-%02d\n",
            days_since, year, month, day, calendar_name, tyear, tmonth, tday );

    days_since = -5;
    if( (ierr = ccs_dayssince( cal, year, month, day, days_since, cal, &tyear, &tmonth, &tday )) != 0 )
        printf( "Calculating %d days since %04d-%02d-%02d in the %s calendar gave error %s\n",
            days_since, year, month, day, calendar_name, ccs_err_str(ierr));
    else
        printf( "%d days since %04d-%02d-%02d in the %s calendar is %04d-%02d-%02d\n",
            days_since, year, month, day, calendar_name, tyear, tmonth, tday );


    /* Free the calendar */
    ccs_free_calendar( cal );

    printf( "\n" );
}

/*=======================================================================*/
int main( int argc, char *argv[] )
{
    do_tests( "Standard", 2010, 1, 6 );    /* Day I'm writing this */
    do_tests( "Standard", 1858, 11, 16);    /* Wikipedia: Jul Day # 2,400,000 */
    do_tests( "Standard", 2132, 8, 31);    /* Wikipedia: Jul Day # 2,500,000 */

    /* Try some dates around the calendar transition dates for fun */
    do_tests( "Standard", 1582, 10, 4 );    /* Day before transition in Std cal */
    do_tests( "Standard", 1582, 10, 15 );    /* Day after transition in Std cal */
    do_tests( "Standard", 1582, 10, 9 );    /* Day DOES NOT EXIST in Std cal, should give errors */

    return(0);
}