ref: 99d2e68a6a97fcdf5fe57ae9a6cda87fc142848b
dir: /sys/src/libc/9sys/ctime.c/
/* * This routine converts time as follows. * The epoch is 0000 Jan 1 1970 GMT. * The argument time is in seconds since then. * The localtime(t) entry returns a pointer to an array * containing * * seconds (0-59) * minutes (0-59) * hours (0-23) * day of month (1-31) * month (0-11) * year-1970 * weekday (0-6, Sun is 0) * day of the year * daylight savings flag * * The routine gets the daylight savings time from the environment. * * asctime(tvec)) * where tvec is produced by localtime * returns a ptr to a character string * that has the ascii time in the form * * \\ * Thu Jan 01 00:00:00 GMT 1970n0 * 012345678901234567890123456789 * 0 1 2 * * ctime(t) just calls localtime, then asctime. */ #include <u.h> #include <libc.h> static char dmsize[12] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }; /* * The following table is used for 1974 and 1975 and * gives the day number of the first day after the Sunday of the * change. */ static int dysize(int); static void ct_numb(char*, int); #define TZSIZE 150 static void readtimezone(void); static int rd_name(char**, char*); static int rd_long(char**, long*); static struct { char stname[4]; char dlname[4]; long stdiff; long dldiff; long dlpairs[TZSIZE]; } timezone; char* ctime(long t) { return asctime(localtime(t)); } Tm* localtime(long tim) { Tm *ct; long t, *p; int dlflag; if(timezone.stname[0] == 0) readtimezone(); t = tim + timezone.stdiff; dlflag = 0; for(p = timezone.dlpairs; *p; p += 2) if(t >= p[0]) if(t < p[1]) { t = tim + timezone.dldiff; dlflag++; break; } ct = gmtime(t); if(dlflag){ strcpy(ct->zone, timezone.dlname); ct->tzoff = timezone.dldiff; } else { strcpy(ct->zone, timezone.stname); ct->tzoff = timezone.stdiff; } return ct; } Tm* gmtime(long tim) { int d0, d1; long hms, day; static Tm xtime; /* * break initial number into days */ hms = tim % 86400L; day = tim / 86400L; if(hms < 0) { hms += 86400L; day -= 1; } /* * generate hours:minutes:seconds */ xtime.sec = hms % 60; d1 = hms / 60; xtime.min = d1 % 60; d1 /= 60; xtime.hour = d1; /* * day is the day number. * generate day of the week. * The addend is 4 mod 7 (1/1/1970 was Thursday) */ xtime.wday = (day + 7340036L) % 7; /* * year number */ if(day >= 0) for(d1 = 1970; day >= dysize(d1); d1++) day -= dysize(d1); else for (d1 = 1970; day < 0; d1--) day += dysize(d1-1); xtime.year = d1-1900; xtime.yday = d0 = day; /* * generate month */ if(dysize(d1) == 366) dmsize[1] = 29; for(d1 = 0; d0 >= dmsize[d1]; d1++) d0 -= dmsize[d1]; dmsize[1] = 28; xtime.mday = d0 + 1; xtime.mon = d1; strcpy(xtime.zone, "GMT"); return &xtime; } char* asctime(Tm *t) { char *ncp; static char cbuf[30]; strcpy(cbuf, "Thu Jan 01 00:00:00 GMT 1970\n"); ncp = &"SunMonTueWedThuFriSat"[t->wday*3]; cbuf[0] = *ncp++; cbuf[1] = *ncp++; cbuf[2] = *ncp; ncp = &"JanFebMarAprMayJunJulAugSepOctNovDec"[t->mon*3]; cbuf[4] = *ncp++; cbuf[5] = *ncp++; cbuf[6] = *ncp; ct_numb(cbuf+8, t->mday); ct_numb(cbuf+11, t->hour+100); ct_numb(cbuf+14, t->min+100); ct_numb(cbuf+17, t->sec+100); ncp = t->zone; cbuf[20] = *ncp++; cbuf[21] = *ncp++; cbuf[22] = *ncp; ct_numb(cbuf+24, (t->year+1900) / 100 + 100); ct_numb(cbuf+26, t->year+100); return cbuf; } static dysize(int y) { if(y%4 == 0 && (y%100 != 0 || y%400 == 0)) return 366; return 365; } static void ct_numb(char *cp, int n) { cp[0] = ' '; if(n >= 10) cp[0] = (n/10)%10 + '0'; cp[1] = n%10 + '0'; } static void readtimezone(void) { char buf[TZSIZE*11+30], *p; int i; memset(buf, 0, sizeof(buf)); i = open("/env/timezone", 0); if(i < 0) goto error; if(read(i, buf, sizeof(buf)) >= sizeof(buf)){ close(i); goto error; } close(i); p = buf; if(rd_name(&p, timezone.stname)) goto error; if(rd_long(&p, &timezone.stdiff)) goto error; if(rd_name(&p, timezone.dlname)) goto error; if(rd_long(&p, &timezone.dldiff)) goto error; for(i=0; i<TZSIZE; i++) { if(rd_long(&p, &timezone.dlpairs[i])) goto error; if(timezone.dlpairs[i] == 0) return; } error: timezone.stdiff = 0; strcpy(timezone.stname, "GMT"); timezone.dlpairs[0] = 0; } static rd_name(char **f, char *p) { int c, i; for(;;) { c = *(*f)++; if(c != ' ' && c != '\n') break; } for(i=0; i<3; i++) { if(c == ' ' || c == '\n') return 1; *p++ = c; c = *(*f)++; } if(c != ' ' && c != '\n') return 1; *p = 0; return 0; } static rd_long(char **f, long *p) { int c, s; long l; s = 0; for(;;) { c = *(*f)++; if(c == '-') { s++; continue; } if(c != ' ' && c != '\n') break; } if(c == 0) { *p = 0; return 0; } l = 0; for(;;) { if(c == ' ' || c == '\n') break; if(c < '0' || c > '9') return 1; l = l*10 + c-'0'; c = *(*f)++; } if(s) l = -l; *p = l; return 0; }