1 /* $NetBSD: asctime.c,v 1.20 2014/10/23 18:45:58 christos Exp $ */
2
3 /*
4 ** This file is in the public domain, so clarified as of
5 ** 1996-06-05 by Arthur David Olson.
6 */
7
8 /*
9 ** Avoid the temptation to punt entirely to strftime;
10 ** the output of strftime is supposed to be locale specific
11 ** whereas the output of asctime is supposed to be constant.
12 */
13
14 #include <sys/cdefs.h>
15 #if defined(LIBC_SCCS) && !defined(lint)
16 #if 0
17 static char elsieid[] = "@(#)asctime.c 8.5";
18 #else
19 __RCSID("$NetBSD: asctime.c,v 1.20 2014/10/23 18:45:58 christos Exp $");
20 #endif
21 #endif /* LIBC_SCCS and not lint */
22
23 /*LINTLIBRARY*/
24
25 #include "namespace.h"
26 #include "private.h"
27 #include "tzfile.h"
28
29 #ifdef __weak_alias
__weak_alias(asctime_r,_asctime_r)30 __weak_alias(asctime_r,_asctime_r)
31 #endif
32
33 /*
34 ** Some systems only handle "%.2d"; others only handle "%02d";
35 ** "%02.2d" makes (most) everybody happy.
36 ** At least some versions of gcc warn about the %02.2d;
37 ** we conditionalize below to avoid the warning.
38 */
39 /*
40 ** All years associated with 32-bit time_t values are exactly four digits long;
41 ** some years associated with 64-bit time_t values are not.
42 ** Vintage programs are coded for years that are always four digits long
43 ** and may assume that the newline always lands in the same place.
44 ** For years that are less than four digits, we pad the output with
45 ** leading zeroes to get the newline in the traditional place.
46 ** The -4 ensures that we get four characters of output even if
47 ** we call a strftime variant that produces fewer characters for some years.
48 ** The ISO C 1999 and POSIX 1003.1-2004 standards prohibit padding the year,
49 ** but many implementations pad anyway; most likely the standards are buggy.
50 */
51 #ifdef __GNUC__
52 #define ASCTIME_FMT "%.3s %.3s%3d %2.2d:%2.2d:%2.2d %-4s\n"
53 #else /* !defined __GNUC__ */
54 #define ASCTIME_FMT "%.3s %.3s%3d %02.2d:%02.2d:%02.2d %-4s\n"
55 #endif /* !defined __GNUC__ */
56 /*
57 ** For years that are more than four digits we put extra spaces before the year
58 ** so that code trying to overwrite the newline won't end up overwriting
59 ** a digit within a year and truncating the year (operating on the assumption
60 ** that no output is better than wrong output).
61 */
62 #ifdef __GNUC__
63 #define ASCTIME_FMT_B "%.3s %.3s%3d %2.2d:%2.2d:%2.2d %s\n"
64 #else /* !defined __GNUC__ */
65 #define ASCTIME_FMT_B "%.3s %.3s%3d %02.2d:%02.2d:%02.2d %s\n"
66 #endif /* !defined __GNUC__ */
67
68 #define STD_ASCTIME_BUF_SIZE 26
69 /*
70 ** Big enough for something such as
71 ** ??? ???-2147483648 -2147483648:-2147483648:-2147483648 -2147483648\n
72 ** (two three-character abbreviations, five strings denoting integers,
73 ** seven explicit spaces, two explicit colons, a newline,
74 ** and a trailing NUL byte).
75 ** The values above are for systems where an int is 32 bits and are provided
76 ** as an example; the define below calculates the maximum for the system at
77 ** hand.
78 */
79 #define MAX_ASCTIME_BUF_SIZE (2*3+5*INT_STRLEN_MAXIMUM(int)+7+2+1+1)
80
81 static char buf_asctime[MAX_ASCTIME_BUF_SIZE];
82
83 /*
84 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
85 */
86
87 char *
88 asctime_r(const struct tm *timeptr, char *buf)
89 {
90 static const char wday_name[][3] = {
91 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
92 };
93 static const char mon_name[][3] = {
94 "Jan", "Feb", "Mar", "Apr", "May", "Jun",
95 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
96 };
97 const char * wn;
98 const char * mn;
99 char year[INT_STRLEN_MAXIMUM(int) + 2];
100 char result[MAX_ASCTIME_BUF_SIZE];
101
102 if (timeptr == NULL) {
103 errno = EINVAL;
104 return strcpy(buf, "??? ??? ?? ??:??:?? ????\n");
105 }
106 if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK)
107 wn = "???";
108 else wn = wday_name[timeptr->tm_wday];
109 if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR)
110 mn = "???";
111 else mn = mon_name[timeptr->tm_mon];
112 /*
113 ** Use strftime's %Y to generate the year, to avoid overflow problems
114 ** when computing timeptr->tm_year + TM_YEAR_BASE.
115 ** Assume that strftime is unaffected by other out-of-range members
116 ** (e.g., timeptr->tm_mday) when processing "%Y".
117 */
118 (void) strftime(year, sizeof year, "%Y", timeptr);
119 (void) snprintf(result,
120 sizeof(result),
121 ((strlen(year) <= 4) ? ASCTIME_FMT : ASCTIME_FMT_B),
122 wn, mn,
123 timeptr->tm_mday, timeptr->tm_hour,
124 timeptr->tm_min, timeptr->tm_sec,
125 year);
126 if (strlen(result) < STD_ASCTIME_BUF_SIZE || buf == buf_asctime)
127 return strcpy(buf, result);
128 else {
129 errno = EOVERFLOW;
130 return NULL;
131 }
132 }
133
134 /*
135 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
136 */
137
138 char *
asctime(const struct tm * timeptr)139 asctime(const struct tm *timeptr)
140 {
141 return asctime_r(timeptr, buf_asctime);
142 }
143