1/*	$NetBSD: asctime.c,v 1.30 2024/01/20 14:52:49 christos Exp $	*/
2
3/* asctime and asctime_r a la POSIX and ISO C, except pad years before 1000.  */
4
5/*
6** This file is in the public domain, so clarified as of
7** 1996-06-05 by Arthur David Olson.
8*/
9
10/*
11** Avoid the temptation to punt entirely to strftime;
12** the output of strftime is supposed to be locale specific
13** whereas the output of asctime is supposed to be constant.
14*/
15
16#include <sys/cdefs.h>
17#if defined(LIBC_SCCS) && !defined(lint)
18#if 0
19static char	elsieid[] = "@(#)asctime.c	8.5";
20#else
21__RCSID("$NetBSD: asctime.c,v 1.30 2024/01/20 14:52:49 christos Exp $");
22#endif
23#endif /* LIBC_SCCS and not lint */
24
25/*LINTLIBRARY*/
26
27#include "namespace.h"
28#include "private.h"
29#include <stdio.h>
30
31#ifndef __LIBC12_SOURCE__
32
33#ifdef __weak_alias
34__weak_alias(asctime_r,_asctime_r)
35#endif
36
37/*
38** All years associated with 32-bit time_t values are exactly four digits long;
39** some years associated with 64-bit time_t values are not.
40** Vintage programs are coded for years that are always four digits long
41** and may assume that the newline always lands in the same place.
42** For years that are less than four digits, we pad the output with
43** leading zeroes to get the newline in the traditional place.
44** The -4 ensures that we get four characters of output even if
45** we call a strftime variant that produces fewer characters for some years.
46** The ISO C and POSIX standards prohibit padding the year,
47** but many implementations pad anyway; most likely the standards are buggy.
48*/
49static char const ASCTIME_FMT[] = "%s %s%3d %.2d:%.2d:%.2d %-4s\n";
50/*
51** For years that are more than four digits we put extra spaces before the year
52** so that code trying to overwrite the newline won't end up overwriting
53** a digit within a year and truncating the year (operating on the assumption
54** that no output is better than wrong output).
55*/
56static char const ASCTIME_FMT_B[] = "%s %s%3d %.2d:%.2d:%.2d     %s\n";
57
58enum { STD_ASCTIME_BUF_SIZE = 26 };
59#endif
60
61/*
62** Big enough for something such as
63** ??? ???-2147483648 -2147483648:-2147483648:-2147483648     -2147483648\n
64** (two three-character abbreviations, five strings denoting integers,
65** seven explicit spaces, two explicit colons, a newline,
66** and a trailing NUL byte).
67** The values above are for systems where an int is 32 bits and are provided
68** as an example; the size expression below is a bound for the system at
69** hand.
70*/
71static char buf_ctime[2*3 + 5*INT_STRLEN_MAXIMUM(int) + 7 + 2 + 1 + 1];
72
73/* A similar buffer for ctime.
74   C89 requires that they be the same buffer.
75   This requirement was removed in C99, so support it only if requested,
76   as support is more likely to lead to bugs in badly written programs.  */
77#ifndef __LIBC12_SOURCE__
78#if SUPPORT_C89
79# define buf_asctime buf_ctime
80#else
81static char buf_asctime[sizeof buf_ctime];
82#endif
83
84char *
85asctime_r(struct tm const *restrict timeptr, char *restrict buf)
86{
87	static const char	wday_name[][4] = {
88		"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
89	};
90	static const char	mon_name[][4] = {
91		"Jan", "Feb", "Mar", "Apr", "May", "Jun",
92		"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
93	};
94	const char *	wn;
95	const char *	mn;
96	char			year[INT_STRLEN_MAXIMUM(int) + 2];
97	char result[sizeof buf_ctime];
98
99	if (timeptr == NULL) {
100		errno = EINVAL;
101		return strcpy(buf, "??? ??? ?? ??:??:?? ????\n");
102	}
103	if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK)
104		wn = "???";
105	else	wn = wday_name[timeptr->tm_wday];
106	if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR)
107		mn = "???";
108	else	mn = mon_name[timeptr->tm_mon];
109	/*
110	** Use strftime's %Y to generate the year, to avoid overflow problems
111	** when computing timeptr->tm_year + TM_YEAR_BASE.
112	** Assume that strftime is unaffected by other out-of-range members
113	** (e.g., timeptr->tm_mday) when processing "%Y".
114	*/
115	(void) strftime(year, sizeof year, "%Y", timeptr);
116	(void) snprintf(result,
117		sizeof(result),
118		((strlen(year) <= 4) ? ASCTIME_FMT : ASCTIME_FMT_B),
119		wn, mn,
120		timeptr->tm_mday, timeptr->tm_hour,
121		timeptr->tm_min, timeptr->tm_sec,
122		year);
123	if (strlen(result) < STD_ASCTIME_BUF_SIZE
124	    || buf == buf_ctime || buf == buf_asctime)
125		return strcpy(buf, result);
126	else {
127		errno = EOVERFLOW;
128		return NULL;
129	}
130}
131
132char *
133asctime(const struct tm *timeptr)
134{
135	return asctime_r(timeptr, buf_asctime);
136}
137
138#endif /* !__LIBC12_SOURCE__ */
139
140char *
141ctime_rz(timezone_t sp, const time_t *timep, char *buf)
142{
143  struct tm mytm;
144  struct tm *tmp = localtime_rz(sp, timep, &mytm);
145  return tmp ? asctime_r(tmp, buf) : NULL;
146}
147
148char *
149ctime_r(const time_t *timep, char *buf)
150{
151  struct tm mytm;
152  struct tm *tmp = localtime_r(timep, &mytm);
153  return tmp ? asctime_r(tmp, buf) : NULL;
154}
155
156char *
157ctime(const time_t *timep)
158{
159  return ctime_r(timep, buf_ctime);
160}
161