add_longtime.c

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/*===========================================================================*/
/* DMC Interim     |              add_longtime             |         utility */
/*===========================================================================*/
/*
	Name:		add_longtime
	Purpose:	add a time increment in seconds to time in struct input_time fmt
	Usage:		struct input_time add_longtime ();
				struct input_time time;
				struct input_time newtime;
				long delta;
				newtime = add_longtime (time, delta);
	Input:		time = original time in struct input_time form
				delta = increment>0 in seconds to be added to original time
	Output:		newtime = output time in struct input_time form
	Externals:	none
	Warnings:	none
	Errors:		none
	Called by:	anything
	Calls to:	none
	Algorithm:	convert the input hour, minute, second, fracsec to seconds;
				add total to delta; convert result to days, hours, minutes,
				seconds, and fractional seconds, allowing for change of year.
	Notes:		The time structure looks like:
					struct input_time
					{
						unsigned short int year;
						unsigned short int day;
						char hour;
						char minute;
						char second;
						unsigned short int fracsec;
					};
	Problems:	Ignores leap seconds
	Debug:		level D_MIN -
				level D_MED -
				level D_MAX - print out start and finish notices
	References:	none
	Language:	ANSI standard C
	Author:		Kevin MacKenzie		01 mar 1989
	Revisions:	
*/

#include "output.h"

#define isaleap(year) (((year%100 != 0) && (year%4 == 0)) || (year%400 == 0))

struct	input_time 	add_longtime (time, delta)
struct	input_time 	time;
register long		delta;
{
	struct	input_time 	newtime;			/* result */
	unsigned short int	lenyr;				/* length of year in days */
	char				i;

	if (Debug > D_MAX) fprintf (D_OUT, "[add_longtime] Started.\n");
	/* convert input day time to seconds and add to delta */
	delta += (time.hour*3600) + (time.minute*60) + time.second;

	/* convert delta to days hh:mm:ss.ffff */
	newtime.fracsec = time.fracsec;				/* no change */
	newtime.day = time.day + (unsigned short int) (delta / 86400);
	delta %= 86400L;							/* seconds per day */
	newtime.hour = (char) (delta / 3600L);
	delta %= 3600L;								/* seconds per hour */
	newtime.minute = (char) (delta / 60L);
	delta %= 60L;								/* seconds per minute */
	newtime.second = (char) delta;
	newtime.year = time.year;					/* no change */

	/* if at a year boundary, fixup date, taking leap years into account */
	if (newtime.day > 365)
	{											/* at year boundary */
		lenyr = (isaleap (time.year)) ?  366 : 365; /* get length of year */
		newtime.year += (newtime.day - 1) / lenyr;
		if ((newtime.day %= lenyr) == 0) newtime.day = lenyr;
	}
	if (Debug > D_MAX) fprintf (D_OUT, "[add_longtime] Finished.\n");
	return (newtime);
}