1 /* $OpenBSD: asctime.c,v 1.24 2019/07/03 03:24:04 deraadt Exp $ */
2 /*
3 ** This file is in the public domain, so clarified as of
4 ** 1996-06-05 by Arthur David Olson.
5 */
6
7 /*
8 ** Avoid the temptation to punt entirely to strftime;
9 ** the output of strftime is supposed to be locale specific
10 ** whereas the output of asctime is supposed to be constant.
11 */
12
13 #include <errno.h>
14 #include <stdio.h>
15 #include <string.h>
16 #include "private.h"
17 #include "tzfile.h"
18 #include "thread_private.h"
19
20 /*
21 ** Some systems only handle "%.2d"; others only handle "%02d";
22 ** "%02.2d" makes (most) everybody happy.
23 ** At least some versions of gcc warn about the %02.2d;
24 ** we conditionalize below to avoid the warning.
25 */
26 /*
27 ** All years associated with 32-bit time_t values are exactly four digits long;
28 ** some years associated with 64-bit time_t values are not.
29 ** Vintage programs are coded for years that are always four digits long
30 ** and may assume that the newline always lands in the same place.
31 ** For years that are less than four digits, we pad the output with
32 ** leading zeroes to get the newline in the traditional place.
33 ** The -4 ensures that we get four characters of output even if
34 ** we call a strftime variant that produces fewer characters for some years.
35 ** The ISO C 1999 and POSIX 1003.1-2004 standards prohibit padding the year,
36 ** but many implementations pad anyway; most likely the standards are buggy.
37 */
38 #define ASCTIME_FMT "%.3s %.3s%3d %2.2d:%2.2d:%2.2d %-4s\n"
39
40 /*
41 ** For years that are more than four digits we put extra spaces before the year
42 ** so that code trying to overwrite the newline won't end up overwriting
43 ** a digit within a year and truncating the year (operating on the assumption
44 ** that no output is better than wrong output).
45 */
46 #define ASCTIME_FMT_B "%.3s %.3s%3d %2.2d:%2.2d:%2.2d %s\n"
47
48 #define STD_ASCTIME_BUF_SIZE 26
49 /*
50 ** Big enough for something such as
51 ** ??? ???-2147483648 -2147483648:-2147483648:-2147483648 -2147483648\n
52 ** (two three-character abbreviations, five strings denoting integers,
53 ** seven explicit spaces, two explicit colons, a newline,
54 ** and a trailing ASCII nul).
55 ** The values above are for systems where an int is 32 bits and are provided
56 ** as an example; the define below calculates the maximum for the system at
57 ** hand.
58 */
59 #define MAX_ASCTIME_BUF_SIZE (2*3+5*INT_STRLEN_MAXIMUM(int)+7+2+1+1)
60
61 static char *
asctime3(const struct tm * timeptr,char * buf,int bufsize)62 asctime3(const struct tm *timeptr, char *buf, int bufsize)
63 {
64 static const char wday_name[][4] = {
65 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
66 };
67 static const char mon_name[][4] = {
68 "Jan", "Feb", "Mar", "Apr", "May", "Jun",
69 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
70 };
71 const char * wn;
72 const char * mn;
73 char year[INT_STRLEN_MAXIMUM(int) + 2];
74 int len;
75
76 if (timeptr == NULL) {
77 errno = EINVAL;
78 strlcpy(buf, "??? ??? ?? ??:??:?? ????\n", bufsize);
79 return buf;
80 }
81 if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK)
82 wn = "???";
83 else
84 wn = wday_name[timeptr->tm_wday];
85 if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR)
86 mn = "???";
87 else
88 mn = mon_name[timeptr->tm_mon];
89 /*
90 ** Use strftime's %Y to generate the year, to avoid overflow problems
91 ** when computing timeptr->tm_year + TM_YEAR_BASE.
92 ** Assume that strftime is unaffected by other out-of-range members
93 ** (e.g., timeptr->tm_mday) when processing "%Y".
94 */
95 (void) strftime(year, sizeof year, "%Y", timeptr);
96 len = snprintf(buf, bufsize,
97 ((strlen(year) <= 4) ? ASCTIME_FMT : ASCTIME_FMT_B),
98 wn, mn,
99 timeptr->tm_mday, timeptr->tm_hour,
100 timeptr->tm_min, timeptr->tm_sec,
101 year);
102 if (len >= 0 && len < bufsize) {
103 return buf;
104 } else {
105 errno = EOVERFLOW;
106 return NULL;
107 }
108 }
109
110 /*
111 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
112 */
113
114 char *
asctime_r(const struct tm * timeptr,char * buf)115 asctime_r(const struct tm *timeptr, char *buf)
116 {
117 /*
118 ** P1003 8.3.5.2 says that asctime_r() can only assume at most
119 ** a 26 byte buffer.
120 */
121 return asctime3(timeptr, buf, STD_ASCTIME_BUF_SIZE);
122 }
123 DEF_WEAK(asctime_r);
124
125 /*
126 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
127 */
128
129 char *
asctime(const struct tm * timeptr)130 asctime(const struct tm *timeptr)
131 {
132 static char result[MAX_ASCTIME_BUF_SIZE];
133 _THREAD_PRIVATE_KEY(asctime);
134 char *resultp = (char *)_THREAD_PRIVATE(asctime, result, NULL);
135
136 if (resultp == NULL)
137 return NULL;
138 else
139 return asctime3(timeptr, resultp, sizeof(result));
140 }
141 DEF_STRONG(asctime);
142