cmp_time.c

seed格式数据解压程序,地震分析人员必备

/*===========================================================================*/
/* DMC Interim     |                cmp_time               |         utility */
/*===========================================================================*/
/*
	Name:	cmp_time
	Purpose:compare two times in struct input_time format
	Usage:	int cmp_time ();
			struct input_time time1;
			struct input_time time2;
			long precision;
			int result;
			result = cmp_time (time1, time2, precision);
	Input:	time1 = 1st time in struct input_time format
			time2 = 2nd time in struct input_time format
			precision = comparison precision in e-04 sec >= 0
					(e.g., 50% of sample interval)
	Output:	result =  0 if time1 == time2 (diff <= precision)
			       = -1 if time1 < time2
			       =  1 if time1 > time2
	Externals:	none
	Warnings:	none
	Errors:		none
	Called by:	anything
	Calls to:	none
	Algorithm:
		Compute dates relative to january 1 of the lesser year and
		compare. If difference greater than 2 days, return appropriate
		inequality.  Otherwise, compute daytimes in e-04 sec relative
		to midnite.  Take any difference in date into account and
		compare the times.  If difference <= precision, return an
		equality, else return the appropriate inequality.
	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:Maximum effective precision is 48 hours.
		Tolerances of greater than ~59.65 hours will overflow.
	Debug:	level D_MIN -
		level D_MED -
		level D_MAX - print out start, comparison and finish notices
	References:	none
	Language:	ANSI standard C
	Author:		Kevin MacKenzie		28 mar 1989
	Revisions:
*/

#include "output.h"
#define isaleap(year) (((year%100 != 0) && (year%4 == 0)) || (year%400 == 0))
#define ONEDAY 86400L		/* one day in sec */

int cmp_time (time1, time2, precision)
struct	input_time time1;		/* first time to compare */
struct	input_time time2;		/* second time to compare */
long	precision;              	/* comparison precision, e-04 sec */
{
	register long	diff;		/* value difference */
	register long	dtime1 = 0;	/* daytime #1 in e-04 sec */
	register long 	dtime2 = 0;	/* daytime #2 in e-04 sec */
	unsigned short int lenyr;	/* length of year in days */
	int err;			/* result */

	if (precision < 0) 
		precision = 0;		/* precision must be >= 0 */

	/* compare years */

	diff = (long)time1.year - (long)time2.year;	

	if (diff == 0)
		;	/* difference < 1 year */
	else 
	if (diff == 1) 
	{	
		/* difference near year end */ 
		lenyr = (isaleap (time2.year)) ? 366 : 365;		

		/* get length of year */ 
		time1.day += lenyr;
	}
	else 
	if (diff == -1)
	{
		/* difference near year end */ 
		lenyr = (isaleap (time1.year)) ? 366 : 365;	

		/* get length of year */
		time2.day += lenyr;

	}
	else 
	if (diff >  1)
		return (err = 1);	/* time1 >>> time2 */
	else 
	if (diff < -1)
		return (err = -1);	/* time1 <<< time2 */

	/* compare dates */

	diff = (long)time1.day - (long)time2.day;

	if (diff > 1)
		return (err = 1);	/* time1 >> time2 */
	else 
	if (diff < -1)
		return (err = -1);	/* time1 << time2 */
	else 
	{
		/* difference < 2 days */ 
		dtime1 += diff * ONEDAY;

		/* difference in dates */
		dtime1 += (time1.hour*3600)+(time1.minute*60)+time1.second;

		/* sec*/
		dtime1 *= 10000;

		/* convert sec to e-04 sec*/
		dtime1 += time1.fracsec;

		dtime2 += (time2.hour*3600)+(time2.minute*60)+time2.second;
		
		/* sec*/
		dtime2 *= 10000;

		/* convert sec to e-04 sec*/

		dtime2 += time2.fracsec;

	}

	/* compare daytimes */
	if (dtime1 - dtime2 > precision)
		return (err = 1);		/* time1 > time2 */
	else 
	if (dtime2 - dtime1 > precision)
		return (err = -1);		/* time1 < time2 */

	return (err = 0);			/* time1 == time2 */
}