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Annotation of 41BSD/libc/gen/ctime.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * This routine converts time as follows.
        !             3:  * The epoch is 0000 Jan 1 1970 GMT.
        !             4:  * The argument time is in seconds since then.
        !             5:  * The localtime(t) entry returns a pointer to an array
        !             6:  * containing
        !             7:  *  seconds (0-59)
        !             8:  *  minutes (0-59)
        !             9:  *  hours (0-23)
        !            10:  *  day of month (1-31)
        !            11:  *  month (0-11)
        !            12:  *  year-1970
        !            13:  *  weekday (0-6, Sun is 0)
        !            14:  *  day of the year
        !            15:  *  daylight savings flag
        !            16:  *
        !            17:  * The routine calls the system to determine the local
        !            18:  * timezone and whether Daylight Saving Time is permitted locally.
        !            19:  * (DST is then determined by the current US standard rules)
        !            20:  * There is a table that accounts for the peculiarities
        !            21:  * undergone by daylight time in 1974-1975.
        !            22:  *
        !            23:  * The routine does not work
        !            24:  * in Saudi Arabia which runs on Solar time.
        !            25:  *
        !            26:  * asctime(tvec))
        !            27:  * where tvec is produced by localtime
        !            28:  * returns a ptr to a character string
        !            29:  * that has the ascii time in the form
        !            30:  *     Thu Jan 01 00:00:00 1970n0\\
        !            31:  *     01234567890123456789012345
        !            32:  *     0         1         2
        !            33:  *
        !            34:  * ctime(t) just calls localtime, then asctime.
        !            35:  */
        !            36: 
        !            37: #include <time.h>
        !            38: #include <sys/types.h>
        !            39: #include <sys/timeb.h>
        !            40: 
        !            41: static char    cbuf[26];
        !            42: static int     dmsize[12] =
        !            43: {
        !            44:        31,
        !            45:        28,
        !            46:        31,
        !            47:        30,
        !            48:        31,
        !            49:        30,
        !            50:        31,
        !            51:        31,
        !            52:        30,
        !            53:        31,
        !            54:        30,
        !            55:        31
        !            56: };
        !            57: 
        !            58: /*
        !            59:  * The following table is used for 1974 and 1975 and
        !            60:  * gives the day number of the first day after the Sunday of the
        !            61:  * change.
        !            62:  */
        !            63: static struct {
        !            64:        int     daylb;
        !            65:        int     dayle;
        !            66: } daytab[] = {
        !            67:        5,      333,    /* 1974: Jan 6 - last Sun. in Nov */
        !            68:        58,     303,    /* 1975: Last Sun. in Feb - last Sun in Oct */
        !            69: };
        !            70: 
        !            71: struct tm      *gmtime();
        !            72: char           *ct_numb();
        !            73: struct tm      *localtime();
        !            74: char   *ctime();
        !            75: char   *ct_num();
        !            76: char   *asctime();
        !            77: 
        !            78: char *
        !            79: ctime(t)
        !            80: long *t;
        !            81: {
        !            82:        return(asctime(localtime(t)));
        !            83: }
        !            84: 
        !            85: struct tm *
        !            86: localtime(tim)
        !            87: long *tim;
        !            88: {
        !            89:        register int dayno;
        !            90:        register struct tm *ct;
        !            91:        register daylbegin, daylend;
        !            92:        long copyt;
        !            93:        struct timeb systime;
        !            94: 
        !            95:        ftime(&systime);
        !            96:        copyt = *tim - (long)systime.timezone*60;
        !            97:        ct = gmtime(&copyt);
        !            98:        dayno = ct->tm_yday;
        !            99:        daylbegin = 119;        /* last Sun in Apr */
        !           100:        daylend = 303;          /* Last Sun in Oct */
        !           101:        if (ct->tm_year==74 || ct->tm_year==75) {
        !           102:                daylbegin = daytab[ct->tm_year-74].daylb;
        !           103:                daylend = daytab[ct->tm_year-74].dayle;
        !           104:        }
        !           105:        daylbegin = sunday(ct, daylbegin);
        !           106:        daylend = sunday(ct, daylend);
        !           107:        if (systime.dstflag &&
        !           108:            (dayno>daylbegin || (dayno==daylbegin && ct->tm_hour>=2)) &&
        !           109:            (dayno<daylend || (dayno==daylend && ct->tm_hour<1))) {
        !           110:                copyt += 1*60*60;
        !           111:                ct = gmtime(&copyt);
        !           112:                ct->tm_isdst++;
        !           113:        }
        !           114:        return(ct);
        !           115: }
        !           116: 
        !           117: /*
        !           118:  * The argument is a 0-origin day number.
        !           119:  * The value is the day number of the first
        !           120:  * Sunday on or after the day.
        !           121:  */
        !           122: static
        !           123: sunday(t, d)
        !           124: register struct tm *t;
        !           125: register int d;
        !           126: {
        !           127:        if (d >= 58)
        !           128:                d += dysize(t->tm_year) - 365;
        !           129:        return(d - (d - t->tm_yday + t->tm_wday + 700) % 7);
        !           130: }
        !           131: 
        !           132: struct tm *
        !           133: gmtime(tim)
        !           134: long *tim;
        !           135: {
        !           136:        register int d0, d1;
        !           137:        long hms, day;
        !           138:        register int *tp;
        !           139:        static struct tm xtime;
        !           140: 
        !           141:        /*
        !           142:         * break initial number into days
        !           143:         */
        !           144:        hms = *tim % 86400;
        !           145:        day = *tim / 86400;
        !           146:        if (hms<0) {
        !           147:                hms += 86400;
        !           148:                day -= 1;
        !           149:        }
        !           150:        tp = (int *)&xtime;
        !           151: 
        !           152:        /*
        !           153:         * generate hours:minutes:seconds
        !           154:         */
        !           155:        *tp++ = hms%60;
        !           156:        d1 = hms/60;
        !           157:        *tp++ = d1%60;
        !           158:        d1 /= 60;
        !           159:        *tp++ = d1;
        !           160: 
        !           161:        /*
        !           162:         * day is the day number.
        !           163:         * generate day of the week.
        !           164:         * The addend is 4 mod 7 (1/1/1970 was Thursday)
        !           165:         */
        !           166: 
        !           167:        xtime.tm_wday = (day+7340036)%7;
        !           168: 
        !           169:        /*
        !           170:         * year number
        !           171:         */
        !           172:        if (day>=0) for(d1=70; day >= dysize(d1); d1++)
        !           173:                day -= dysize(d1);
        !           174:        else for (d1=70; day<0; d1--)
        !           175:                day += dysize(d1-1);
        !           176:        xtime.tm_year = d1;
        !           177:        xtime.tm_yday = d0 = day;
        !           178: 
        !           179:        /*
        !           180:         * generate month
        !           181:         */
        !           182: 
        !           183:        if (dysize(d1)==366)
        !           184:                dmsize[1] = 29;
        !           185:        for(d1=0; d0 >= dmsize[d1]; d1++)
        !           186:                d0 -= dmsize[d1];
        !           187:        dmsize[1] = 28;
        !           188:        *tp++ = d0+1;
        !           189:        *tp++ = d1;
        !           190:        xtime.tm_isdst = 0;
        !           191:        return(&xtime);
        !           192: }
        !           193: 
        !           194: char *
        !           195: asctime(t)
        !           196: struct tm *t;
        !           197: {
        !           198:        register char *cp, *ncp;
        !           199:        register int *tp;
        !           200: 
        !           201:        cp = cbuf;
        !           202:        for (ncp = "Day Mon 00 00:00:00 1900\n"; *cp++ = *ncp++;);
        !           203:        ncp = &"SunMonTueWedThuFriSat"[3*t->tm_wday];
        !           204:        cp = cbuf;
        !           205:        *cp++ = *ncp++;
        !           206:        *cp++ = *ncp++;
        !           207:        *cp++ = *ncp++;
        !           208:        cp++;
        !           209:        tp = &t->tm_mon;
        !           210:        ncp = &"JanFebMarAprMayJunJulAugSepOctNovDec"[(*tp)*3];
        !           211:        *cp++ = *ncp++;
        !           212:        *cp++ = *ncp++;
        !           213:        *cp++ = *ncp++;
        !           214:        cp = ct_numb(cp, *--tp);
        !           215:        cp = ct_numb(cp, *--tp+100);
        !           216:        cp = ct_numb(cp, *--tp+100);
        !           217:        cp = ct_numb(cp, *--tp+100);
        !           218:        if (t->tm_year>=100) {
        !           219:                cp[1] = '2';
        !           220:                cp[2] = '0';
        !           221:        }
        !           222:        cp += 2;
        !           223:        cp = ct_numb(cp, t->tm_year+100);
        !           224:        return(cbuf);
        !           225: }
        !           226: 
        !           227: dysize(y)
        !           228: {
        !           229:        if((y%4) == 0)
        !           230:                return(366);
        !           231:        return(365);
        !           232: }
        !           233: 
        !           234: static char *
        !           235: ct_numb(cp, n)
        !           236: register char *cp;
        !           237: {
        !           238:        cp++;
        !           239:        if (n>=10)
        !           240:                *cp++ = (n/10)%10 + '0';
        !           241:        else
        !           242:                *cp++ = ' ';
        !           243:        *cp++ = n%10 + '0';
        !           244:        return(cp);
        !           245: }

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