ascdate.c

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/* ascdate.c - ascdate */

#include <xinu.h>
#include <stdio.h>

struct dateinfo Date = {0, FALSE, DATE_DST_AUTO,
               {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
               {"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul",
                "Aug", "Sep","Oct","Nov","Dec"},
               {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"}};

/*------------------------------------------------------------------------
 *  ascdate  -  Format a date in ascii including day, year hours:mins:secs
 *------------------------------------------------------------------------
 */
status  ascdate (
      uint32    now,        /* Date and time in xinu format */
      char      *str        /* String ( >= 20 chars long)   */
    )
{
    uint32  tmp;            /* Counts remaining seconds */
                    /*   during computations    */
    int32   year, month, day,   /* Values for various parts of  */
        hour, minute, second;   /*   the date           */
    uint32  days;           /* Number of days in a year */
    uint32  leapyrs;        /* Number of leap years between */
                    /*   1970 and now       */
    uint32  shift;          /* Number of times the calendar */
                    /*   shifted by a day       */
    uint32  dayofweek;      /* Day of the week (0 - 6)  */
                    /* For DST, day of the week for:*/
    int32   jan1;           /*   January 1 this year    */
    int32   mar1;           /*   March 1 this year      */
    int32   nov1;           /*   November 1 this year   */
    int32   marss;          /* Day of second sunday in march*/
    int32   novfs;          /* Day of second sunday in march*/
    bool8   dst;            /* Should we adjust for DST?    */
    int32   i;          /* Indexes through months   */

    char    *zones[]  = {"EST", "CST", "MST", "PST"};
    char    *dzones[] = {"EDT", "CDT", "MDT", "PDT"};

    /* Compute the year (1970-2099) */

    for (year=1970 ; TRUE ; year++) {
        days = isleap(year) ? 366 : 365;
        tmp = days * SECPERDY;
        if (tmp > now)
            break;
        now -= tmp;
    }

    /* Compute the number of whole days that have already passed    */
    /*   during the current year (0 through 365)            */

    days = now / SECPERDY;

    /* Compute the month (0-11) */

    for (month=0 ; month<12 ; month++) {
        tmp = Date.dt_msize[month] * SECPERDY;
        if ((month == 1) && isleap(year)) {
            tmp += SECPERDY;
        }
        if (tmp > now)
            break;
        now -= tmp;
    }

    /* Compute the day of month (1-31) */

    day = (int32)( now/SECPERDY ) + 1;
    now %= SECPERDY;

    /* Compute the hour (0-23) */

    hour = (int32) ( now/SECPERHR );
    now %= SECPERHR;

    /* Compute the minutes (0-59) */

    minute = now / SECPERMN;
    now %= SECPERMN;

    /* Compute the seconds (0-59) */
    second = (int32) now;

    /* Compute the day of the week (0-6)                */
    /*                              */
    /*   Note: Jan 1, 1970 was a Thursday (4 on a 0 to 6 range) */
    /* Add one day of the week each full year (365%7 == 1) plus */
    /*    one extra day for each leap year              */

    /* Compute number of leap years prior to current year */

    leapyrs = (year-1969)/4;

    /* Compute shift for all previous years (i.e., day of week of   */
    /* Jan 1 of the current year)                   */

    shift = 4 + (year - 1970) + leapyrs;

    /* Remember day of the week for Jan 1 this year (for DST)   */

    jan1 = shift % 7;

    /* Add the number of days so far this year */

    shift += days;

    /* Convert to integer from 0 through 6 */

    dayofweek = shift % 7;

    /*                              */
    /*      Handle daylight savings time            */
    /*                              */
    /*   Date.dt_daylight specifies whether to set it on, off,  */
    /*      or automatically compute the setting        */
    /*                              */

    dst = FALSE;
    if (Date.dt_daylight == DATE_DST_ON) {
        dst = TRUE;
    } else if (Date.dt_daylight == DATE_DST_AUTO) {
        
        /* Automatic DST calculation: DST is on between 2:00 AM */
        /*   the second Sunday of March and 2:00 AM the first   */
        /*   sunday in November                 */

        /* Calculate day of the week for March 1        */

        mar1 = (jan1 + Date.dt_msize[0] + Date.dt_msize[1] +
                            isleap(year)) % 7;

        /* Caculate day (1-31) of the second sunday in March    */

        if (mar1 == 0) {    /* Mar. 1 is a Sunday       */
            marss = 8;
        } else {        /* Mar. 1 is Monday - Saturday  */
            marss = 15 - mar1;
        }

        /* Calculate day of the week for November 1     */

        nov1 = jan1;
        for (i=0; i<10; i++) {
            nov1 += Date.dt_msize[i];
        }
        if (isleap(year)) {
            nov1++;
        }
        nov1 = nov1 % 7;
        if (nov1 == 0) {    /* Nov. 1 is a Sunday       */
            novfs = 1;
        } else {        /* Nov. 1 is Monday - Saturday  */
            novfs = 8 - nov1;
        }

        /* Set dst based on time of the year */

        /* DST is off during December, January, and Feburary */

        if ( (month == 11) || (month == 0) || (month == 1) ) {
            dst = FALSE;

        /* DST is on from April through October */

        } else if ( (month>2) && (month<10) ) {
            dst = TRUE;

        /* DST is on in March past 2 AM on the second Sunday    */

        } else if (month == 2) {

            dst = FALSE;
            if (day > marss) {
                dst = TRUE;
            } else if ( (day == marss) && (hour >= 2) ) {
                dst = TRUE;
            }

        /* DST is on in November until 2 am on first Sunday */


        } else if (month == 10) {

            dst = TRUE;
            if (day > novfs) {
                dst = FALSE;
            } else if ( (day == novfs) && (hour >= 1) ) {
                dst = FALSE;
            }
        }
    }

    /* If we are doing DST, move ahead one hour and handle the  */
    /*   case where we move to the next day or the next month   */

    if (dst) {
        hour++;

        /* If day exceeded, move to next day */

        if (hour > 23) {
            hour = 0;
            day++;

            /* If month exceeded, move to next month */

            if (day > Date.dt_msize[month]) {
                day = 1;
                month++;

                /* Stop here because DST does not occur */
                /*  during the year boundary        */
            }
        }
    }

    sprintf(str, "%3s  %3s %2d  %2d:%02d:%02d %s %d",
        Date.dt_dnam[dayofweek], Date.dt_mnam[month],
        day, hour, minute, second, dst? dzones[TIMEZONE-5]:
            zones[TIMEZONE-5], year);
    return OK;
}