timeadd.c

解吸SEED格式的源代码

/*===========================================================================*/
/* SEED reader     |              timeadd                  |         utility */
/*===========================================================================*/
/*
	Name:	timeadd
	Purpose:add some number of seconds to a time of the form yyyyddd
		hh:mm:ss.ffff
	Usage:	struct time timeadd ();
		struct time time;
		struct time newtime;
		int increment;
		newtime = timeadd (time, increment);
	Input:	time = the original time in struct time form (see Notes)
		increment = number of seconds to add to time
	Output:	newtime = the resultant time in struct time form (see Notes)
	Externals:	none
	Warnings:	none
	Errors:		none
	Called by:	anything
	Calls to:	none
	Algorithm:convert the input time, exclusive of year and day, to seconds;
	add increment number of seconds to time; convert result to
	hours, minutes, seconds, and fractional seconds, allowing for
	change of day and year.
	Notes:		The time structure looks like:
			struct time
				{
					int year;
					int day;
					int hour;
					int minute;
					int second;
					int fracsec;
				};
	Problems:Gives incorrect result if there was a leap second at the year
			boundary
			Gives incorrect result if increment > 1 year
	References:	none
	Language:	C, hopefully ANSI standard
	Author:		Dennis O'Neill
	Revisions:	07/15/88  Dennis O'Neill  Initial preliminary release 0.9
			11/21/88  Dennis O'Neill  Production release 1.0

	CL - changed increment to unsigned

*/

#include "rdseed.h"

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

struct time timeadd (time, increment)
struct time time;
unsigned int increment;
{
	struct time newtime;			/* result */
	struct time timeinc;			/* time increment */
	int addterm;

	/* initialize year and day */
	newtime.year = time.year;
	newtime.day = time.day;

	/* convert increment to hh:mm:ss.ffff */
	timeinc.fracsec = increment % 10000;
	increment = increment / 10000;
	timeinc.hour = increment / 3600;
	timeinc.minute = (increment - (timeinc.hour * 3600)) / 60;
	timeinc.second = increment - (timeinc.hour * 3600) - (timeinc.minute * 60);

	/* add the increment to the original time */
	newtime.hour = time.hour + timeinc.hour;
	newtime.minute = time.minute + timeinc.minute;
	newtime.second = time.second + timeinc.second;
	newtime.fracsec = time.fracsec + timeinc.fracsec;

	/* adjust fractional seconds, increment seconds if necessary */
	if (newtime.fracsec >= 10000)
	{
		addterm = newtime.fracsec / 10000;
		newtime.second = newtime.second + addterm;
		newtime.fracsec -= 10000 * addterm;
	}

	/* adjust seconds, increment minutes if necessary */
	if (newtime.second >= 60)
	{
		addterm = newtime.second / 60;
		newtime.minute = newtime.minute + addterm;
		newtime.second -= 60 * addterm;
	}

	/* adjust minutes, increment hours if necessary */
	if (newtime.minute >= 60)
	{
		addterm = newtime.minute / 60;
		newtime.hour = newtime.hour + addterm;
		newtime.minute -= 60 * addterm;
	}

	/* adjust hours, increment days if necessary */
	if (newtime.hour >= 24)
	{
		addterm = newtime.hour / 24;
		newtime.day = newtime.day + addterm;
		newtime.hour -= 24 * addterm;
	}

	/* increment year if necessary, allowing for leap year */
	if ((!isaleap (time.year)) && (newtime.day > 365))
	{
		newtime.year += 1;
		newtime.day -= 365;
	}
	else if ((isaleap (time.year)) && (newtime.day > 366))
	{
		newtime.year += 1;
		newtime.day -=366;
	}

	return (newtime);
}


/* -------------------------------------------------------------------------------- */

struct time timesub(time, decrement)
struct time time;
unsigned int decrement;
{
	struct time newtime;			/* result */
	struct time timedec;			/* time increment */

	/* initialize year and day */
	newtime.year = time.year;
	newtime.day = time.day;

	/* convert decrement to hh:mm:ss.ffff */
	timedec.fracsec = decrement % 10000;
	decrement = decrement / 10000;
	timedec.hour = decrement / 3600;
	timedec.minute = (decrement - (timedec.hour * 3600)) / 60;
	timedec.second = decrement - (timedec.hour * 3600) - (timedec.minute * 60);

	/* sub the decrement to the original time */
	newtime.hour = time.hour - timedec.hour;
	newtime.minute = time.minute - timedec.minute;
	newtime.second = time.second - timedec.second;
	newtime.fracsec = time.fracsec - timedec.fracsec;

	/* adjust fractional seconds, decrement seconds if necessary */
	if (newtime.fracsec < 0)
	{
		newtime.second--;
		newtime.fracsec += 10000;
	}

	/* adjust seconds, decrements minutes if necessary */
	if (newtime.second < 0)
	{
		newtime.minute--;
		newtime.second += 60;
	}

	/* adjust minutes, decrement hours if necessary */
	if (newtime.minute < 0)
	{
		newtime.hour--;
		newtime.minute += 60;
	}

	/* adjust hours, decrement days if necessary */
	if (newtime.hour < 0)
	{
		newtime.day--;
		newtime.hour += 24;
	}

	/* decrement year if necessary, allowing for leap year */
	if (newtime.day <= 0)
	{
		newtime.year--;
	
		if (isaleap(newtime.year))
			newtime.day = 366;
		else
			newtime.day = 365;
	}

	return (newtime);
}