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


/* MS-DOS time/date conversion routines derived from: */

/*
 *  linux/fs/msdos/misc.c
 *
 *  Written 1992,1993 by Werner Almesberger
 */

/* Linear day numbers of the respective 1sts in non-leap years. */

static int day_n[] = { 0,31,59,90,120,151,181,212,243,273,304,334,0,0,0,0 };
		  /* JanFebMarApr May Jun Jul Aug Sep Oct Nov Dec */


/* Convert a MS-DOS time/date pair to a UNIX date (seconds since 1 1 70). */

int date_dos2unix(unsigned short time,unsigned short date)
{
    int month, year, secs;

    month = ((date >> 5) & 15)-1;
    year = date >> 9;
    secs = (time & 31)*2+60*((time >> 5) & 63)+(time >> 11)*3600+86400*
	    ((date & 31)-1+day_n[month]+(year/4)+year*365-((year & 3) == 0 &&
	    month < 2 ? 1 : 0)+3653);
	    /* days since 1.1.70 plus 80's leap day */
    return secs;
}


/* Convert linear UNIX date to a MS-DOS time/date pair. */

void date_unix2dos(int unix_date,unsigned short *time,
    unsigned short *date)
{
    int day, year, nl_day, month;

    *time = (unix_date % 60)/2+(((unix_date/60) % 60) << 5)+
	    (((unix_date/3600) % 24) << 11);
    day = unix_date/86400-3652;
    year = day/365;
    if ((year+3)/4+365*year > day) year--;
    day -= (year+3)/4+365*year;
    if (day == 59 && !(year & 3)) {
	nl_day = day;
	month = 2;
    } else {
	nl_day = (year & 3) || day <= 59 ? day : day-1;
	for (month = 0; month < 12; month++)
	    if (day_n[month] > nl_day) break;
    }
    *date = nl_day-day_n[month-1]+1+(month << 5)+(year << 9);
}

/* Convert yapp format 8 hex characters into Unix time */

int yapp2unix(char * ytime)
{
    int i;
    unsigned short time, date;
    if (strlen(ytime) != 8) return 0;
    for(i = 0; i < 8; i++) if (! isxdigit(ytime[i])) return 0;	
    time = strtoul(ytime+4, (char **)NULL, 16);
    ytime[4]=0;
    date = strtoul(ytime, (char **)NULL, 16);
    return(date_dos2unix(time, date));
}

/* Convert unix time to 8 character yapp hex format */

void unix2yapp(int unix_date, char * buffer)
{
    unsigned short time, date;
    date_unix2dos(unix_date, &time, &date);
    sprintf(buffer, "%04X%04X", date, time);
}
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