UNIX 7th Ed. - /usr/src/libc/gen/ctime.c

   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: }

Defined functions

Defined variables