1 #include "../hdr/macros.h"
2 
3 SCCSID(@(#)ctime.c	4.2);
4 
5 /*
6  * This routine converts time as follows.
7  * The epoch is 0000 Jan 1 1970 GMT.
8  * The argument time is in seconds since then.
9  * The localtime(t) entry returns a pointer to an array
10  * containing
11  *  seconds (0-59)
12  *  minutes (0-59)
13  *  hours (0-23)
14  *  day of month (1-31)
15  *  month (0-11)
16  *  year-1970
17  *  weekday (0-6, Sun is 0)
18  *  day of the year
19  *  daylight savings flag
20  *
21  * The routine calls the system to determine the local
22  * timezone and whether Daylight Saving Time is permitted locally.
23  * (DST is then determined by the current US standard rules)
24  * There is a table that accounts for the peculiarities
25  * undergone by daylight time in 1974-1975.
26  *
27  * The routine does not work
28  * in Saudi Arabia which runs on Solar time.
29  *
30  * asctime(tvec))
31  * where tvec is produced by localtime
32  * returns a ptr to a character string
33  * that has the ascii time in the form
34  *	Thu Jan 01 00:00:00 1970n0\\
35  *	01234567890123456789012345
36  *	0	  1	    2
37  *
38  * ctime(t) just calls localtime, then asctime.
39  */
40 
41 #include <sys/time.h>
42 #include <sys/types.h>
43 #include <sys/timeb.h>
44 
45 static	char	cbuf[26];
46 int	dmsize[12] =
47 {
48 	31,
49 	28,
50 	31,
51 	30,
52 	31,
53 	30,
54 	31,
55 	31,
56 	30,
57 	31,
58 	30,
59 	31
60 };
61 
62 /*
63  * The following table is used for 1974 and 1975 and
64  * gives the day number of the first day after the Sunday of the
65  * change.
66  */
67 static struct {
68 	int	daylb;
69 	int	dayle;
70 } daytab[] = {
71 	5,	333,	/* 1974: Jan 6 - last Sun. in Nov */
72 	58,	303,	/* 1975: Last Sun. in Feb - last Sun in Oct */
73 };
74 
75 struct tm	*gmtime();
76 char		*ct_numb();
77 struct tm	*localtime();
78 char	*ctime();
79 char	*ct_num();
80 char	*asctime();
81 
82 char *
83 ctime(t)
84 long *t;
85 {
86 	return(asctime(localtime(t)));
87 }
88 
89 struct tm *
90 localtime(tim)
91 long *tim;
92 {
93 	register int dayno;
94 	register struct tm *ct;
95 	register daylbegin, daylend;
96 	long copyt;
97 	struct timeb systime;
98 
99 	ftime(&systime);
100 	copyt = *tim - (long)systime.timezone*60;
101 	ct = gmtime(&copyt);
102 	dayno = ct->tm_yday;
103 	daylbegin = 119;	/* last Sun in Apr */
104 	daylend = 303;		/* Last Sun in Oct */
105 	if (ct->tm_year==74 || ct->tm_year==75) {
106 		daylbegin = daytab[ct->tm_year-74].daylb;
107 		daylend = daytab[ct->tm_year-74].dayle;
108 	}
109 	daylbegin = sunday(ct, daylbegin);
110 	daylend = sunday(ct, daylend);
111 	if (systime.dstflag &&
112 	    (dayno>daylbegin || (dayno==daylbegin && ct->tm_hour>=2)) &&
113 	    (dayno<daylend || (dayno==daylend && ct->tm_hour<1))) {
114 		copyt += 1*60*60;
115 		ct = gmtime(&copyt);
116 		ct->tm_isdst++;
117 	}
118 	return(ct);
119 }
120 
121 /*
122  * The argument is a 0-origin day number.
123  * The value is the day number of the first
124  * Sunday on or after the day.
125  */
126 static
127 sunday(t, d)
128 register struct tm *t;
129 register int d;
130 {
131 	if (d >= 58)
132 		d += dysize(t->tm_year) - 365;
133 	return(d - (d - t->tm_yday + t->tm_wday + 700) % 7);
134 }
135 
136 struct tm *
137 gmtime(tim)
138 long *tim;
139 {
140 	register int d0, d1;
141 	long hms, day;
142 	register int *tp;
143 	static struct tm xtime;
144 
145 	/*
146 	 * break initial number into days
147 	 */
148 	hms = *tim % 86400;
149 	day = *tim / 86400;
150 	if (hms<0) {
151 		hms += 86400;
152 		day -= 1;
153 	}
154 	tp = (int *)&xtime;
155 
156 	/*
157 	 * generate hours:minutes:seconds
158 	 */
159 	*tp++ = hms%60;
160 	d1 = hms/60;
161 	*tp++ = d1%60;
162 	d1 /= 60;
163 	*tp++ = d1;
164 
165 	/*
166 	 * day is the day number.
167 	 * generate day of the week.
168 	 * The addend is 4 mod 7 (1/1/1970 was Thursday)
169 	 */
170 
171 	xtime.tm_wday = (day+7340036)%7;
172 
173 	/*
174 	 * year number
175 	 */
176 	if (day>=0) for(d1=70; day >= dysize(d1); d1++)
177 		day -= dysize(d1);
178 	else for (d1=70; day<0; d1--)
179 		day += dysize(d1-1);
180 	xtime.tm_year = d1;
181 	xtime.tm_yday = d0 = day;
182 
183 	/*
184 	 * generate month
185 	 */
186 
187 	if (dysize(d1)==366)
188 		dmsize[1] = 29;
189 	for(d1=0; d0 >= dmsize[d1]; d1++)
190 		d0 -= dmsize[d1];
191 	dmsize[1] = 28;
192 	*tp++ = d0+1;
193 	*tp++ = d1;
194 	xtime.tm_isdst = 0;
195 	return(&xtime);
196 }
197 
198 char *
199 asctime(t)
200 struct tm *t;
201 {
202 	register char *cp, *ncp;
203 	register int *tp;
204 
205 	cp = cbuf;
206 	for (ncp = "Day Mon 00 00:00:00 1900\n"; *cp++ = *ncp++;);
207 	ncp = &"SunMonTueWedThuFriSat"[3*t->tm_wday];
208 	cp = cbuf;
209 	*cp++ = *ncp++;
210 	*cp++ = *ncp++;
211 	*cp++ = *ncp++;
212 	cp++;
213 	tp = &t->tm_mon;
214 	ncp = &"JanFebMarAprMayJunJulAugSepOctNovDec"[(*tp)*3];
215 	*cp++ = *ncp++;
216 	*cp++ = *ncp++;
217 	*cp++ = *ncp++;
218 	cp = ct_numb(cp, *--tp);
219 	cp = ct_numb(cp, *--tp+100);
220 	cp = ct_numb(cp, *--tp+100);
221 	cp = ct_numb(cp, *--tp+100);
222 	if (t->tm_year>=100) {
223 		cp[1] = '2';
224 		cp[2] = '0';
225 	}
226 	cp += 2;
227 	cp = ct_numb(cp, t->tm_year+100);
228 	return(cbuf);
229 }
230 
231 dysize(y)
232 {
233 	if((y%4) == 0)
234 		return(366);
235 	return(365);
236 }
237 
238 static char *
239 ct_numb(cp, n)
240 register char *cp;
241 {
242 	cp++;
243 	if (n>=10)
244 		*cp++ = (n/10)%10 + '0';
245 	else
246 		*cp++ = ' ';
247 	*cp++ = n%10 + '0';
248 	return(cp);
249 }
250