xref: /illumos-gate/usr/src/lib/libc/port/gen/ctime.c (revision 67dbe2be0c0f1e2eb428b89088bb5667e8f0b9f6)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 
22 /*
23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
24  * Use is subject to license terms.
25  */
26 
27 /*	Copyright (c) 1988 AT&T	*/
28 /*	  All Rights Reserved  	*/
29 
30 #pragma ident	"%Z%%M%	%I%	%E% SMI"
31 
32 /*
33  * This routine converts time as follows.
34  * The epoch is 0000 Jan 1 1970 GMT.
35  * The argument time is in seconds since then.
36  * The localtime(t) entry returns a pointer to an array
37  * containing
38  *  seconds (0-59)
39  *  minutes (0-59)
40  *  hours (0-23)
41  *  day of month (1-31)
42  *  month (0-11)
43  *  year-1970
44  *  weekday (0-6, Sun is 0)
45  *  day of the year
46  *  daylight savings flag
47  *
48  * The routine corrects for daylight saving
49  * time and will work in any time zone provided
50  * "timezone" is adjusted to the difference between
51  * Greenwich and local standard time (measured in seconds).
52  * In places like Michigan "daylight" must
53  * be initialized to 0 to prevent the conversion
54  * to daylight time.
55  * There is a table which accounts for the peculiarities
56  * undergone by daylight time in 1974-1975.
57  *
58  * The routine does not work
59  * in Saudi Arabia which runs on Solar time.
60  *
61  * asctime(tvec)
62  * where tvec is produced by localtime
63  * returns a ptr to a character string
64  * that has the ascii time in the form
65  *	Thu Jan 01 00:00:00 1970\n\0
66  *	01234567890123456789012345
67  *	0	  1	    2
68  *
69  * ctime(t) just calls localtime, then asctime.
70  *
71  * tzset() looks for an environment variable named
72  * TZ.
73  * If the variable is present, it will set the external
74  * variables "timezone", "altzone", "daylight", and "tzname"
75  * appropriately. It is called by localtime, and
76  * may also be called explicitly by the user.
77  */
78 
79 #include "lint.h"
80 #include <mtlib.h>
81 #include <sys/types.h>
82 #include <time.h>
83 #include <errno.h>
84 #include <thread.h>
85 #include <synch.h>
86 #include "libc.h"
87 #include "tsd.h"
88 
89 #define	dysize(A) (((A)%4)? 365: 366)
90 #define	CBUFSIZ 26
91 
92 static char *
93 ct_numb(char *cp, int n, char pad)
94 {
95 	cp++;
96 	if (n >= 10)
97 		*cp++ = (n / 10) % 10 + '0';
98 	else
99 		*cp++ = pad;
100 	*cp++ = n % 10 + '0';
101 	return (cp);
102 }
103 
104 /*
105  * POSIX.1c standard version of the function asctime_r.
106  * User gets it via static asctime_r from the header file.
107  */
108 char *
109 __posix_asctime_r(const struct tm *t, char *cbuf)
110 {
111 	char *cp;
112 	const char *ncp;
113 	const char *Date = "Day Mon 00 00:00:00 YYYY\n";
114 	const char *Day  = "SunMonTueWedThuFriSat";
115 	const char *Month = "JanFebMarAprMayJunJulAugSepOctNovDec";
116 
117 	int year = t->tm_year + 1900;
118 
119 	cp = cbuf;
120 	for (ncp = Date; *cp++ = *ncp++; /* */)
121 		;
122 	ncp = Day + (3 * t->tm_wday);
123 	cp = cbuf;
124 	*cp++ = *ncp++;
125 	*cp++ = *ncp++;
126 	*cp++ = *ncp++;
127 	cp++;
128 	ncp = Month + (3 * t->tm_mon);
129 	*cp++ = *ncp++;
130 	*cp++ = *ncp++;
131 	*cp++ = *ncp++;
132 	cp = ct_numb(cp, t->tm_mday, ' ');
133 	cp = ct_numb(cp, t->tm_hour, '0');
134 	cp = ct_numb(cp, t->tm_min, '0');
135 	cp = ct_numb(cp, t->tm_sec, '0');
136 
137 	if (year < 0 || year >= 10000) {
138 		/* Only positive, 4-digit years are supported */
139 		errno = EOVERFLOW;
140 		return (NULL);
141 	}
142 	cp = ct_numb(cp, year / 100, '0');
143 	cp--;
144 	(void) ct_numb(cp, year, '0');
145 	return (cbuf);
146 }
147 
148 /*
149  * POSIX.1c Draft-6 version of the function asctime_r.
150  * It was implemented by Solaris 2.3.
151  */
152 char *
153 asctime_r(const struct tm *t, char *cbuf, int buflen)
154 {
155 	if (buflen < CBUFSIZ) {
156 		errno = ERANGE;
157 		return (NULL);
158 	}
159 	return (__posix_asctime_r(t, cbuf));
160 }
161 
162 char *
163 ctime(const time_t *t)
164 {
165 	char *cbuf = tsdalloc(_T_CTIME, CBUFSIZ, NULL);
166 	struct tm *p;
167 
168 	if (cbuf == NULL)
169 		return (NULL);
170 	p = localtime(t);
171 	if (p == NULL)
172 		return (NULL);
173 	return (__posix_asctime_r(p, cbuf));
174 }
175 
176 char *
177 asctime(const struct tm *t)
178 {
179 	char *cbuf = tsdalloc(_T_CTIME, CBUFSIZ, NULL);
180 
181 	if (cbuf == NULL)
182 		return (NULL);
183 	return (__posix_asctime_r(t, cbuf));
184 }
185