1 /*
2 ** This file is in the public domain, so clarified as of
3 ** 1996-06-05 by Arthur David Olson.
4 */
5
6 /*
7 ** Avoid the temptation to punt entirely to strftime;
8 ** the output of strftime is supposed to be locale specific
9 ** whereas the output of asctime is supposed to be constant.
10 */
11
12 /*LINTLIBRARY*/
13
14 #include "private.h"
15 #include "tzfile.h"
16
17 /*
18 ** Some systems only handle "%.2d"; others only handle "%02d";
19 ** "%02.2d" makes (most) everybody happy.
20 ** At least some versions of gcc warn about the %02.2d;
21 ** we conditionalize below to avoid the warning.
22 */
23 /*
24 ** All years associated with 32-bit time_t values are exactly four digits long;
25 ** some years associated with 64-bit time_t values are not.
26 ** Vintage programs are coded for years that are always four digits long
27 ** and may assume that the newline always lands in the same place.
28 ** For years that are less than four digits, we pad the output with
29 ** leading zeroes to get the newline in the traditional place.
30 ** The -4 ensures that we get four characters of output even if
31 ** we call a strftime variant that produces fewer characters for some years.
32 ** The ISO C 1999 and POSIX 1003.1-2004 standards prohibit padding the year,
33 ** but many implementations pad anyway; most likely the standards are buggy.
34 */
35 #ifdef __GNUC__
36 #define ASCTIME_FMT "%.3s %.3s%3d %2.2d:%2.2d:%2.2d %-4s\n"
37 #else /* !defined __GNUC__ */
38 #define ASCTIME_FMT "%.3s %.3s%3d %02.2d:%02.2d:%02.2d %-4s\n"
39 #endif /* !defined __GNUC__ */
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 #ifdef __GNUC__
47 #define ASCTIME_FMT_B "%.3s %.3s%3d %2.2d:%2.2d:%2.2d %s\n"
48 #else /* !defined __GNUC__ */
49 #define ASCTIME_FMT_B "%.3s %.3s%3d %02.2d:%02.2d:%02.2d %s\n"
50 #endif /* !defined __GNUC__ */
51
52 #define STD_ASCTIME_BUF_SIZE 26
53 /*
54 ** Big enough for something such as
55 ** ??? ???-2147483648 -2147483648:-2147483648:-2147483648 -2147483648\n
56 ** (two three-character abbreviations, five strings denoting integers,
57 ** seven explicit spaces, two explicit colons, a newline,
58 ** and a trailing ASCII nul).
59 ** The values above are for systems where an int is 32 bits and are provided
60 ** as an example; the define below calculates the maximum for the system at
61 ** hand.
62 */
63 #define MAX_ASCTIME_BUF_SIZE (2*3+5*INT_STRLEN_MAXIMUM(int)+7+2+1+1)
64
65 static char buf_asctime[MAX_ASCTIME_BUF_SIZE];
66
67 /*
68 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
69 */
70
71 char *
asctime_r(register const struct tm * timeptr,char * buf)72 asctime_r(register const struct tm *timeptr, char *buf)
73 {
74 static const char wday_name[][3] = {
75 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
76 };
77 static const char mon_name[][3] = {
78 "Jan", "Feb", "Mar", "Apr", "May", "Jun",
79 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
80 };
81 register const char * wn;
82 register const char * mn;
83 char year[INT_STRLEN_MAXIMUM(int) + 2];
84 char result[MAX_ASCTIME_BUF_SIZE];
85
86 if (timeptr == NULL) {
87 errno = EINVAL;
88 return strcpy(buf, "??? ??? ?? ??:??:?? ????\n");
89 }
90 if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK)
91 wn = "???";
92 else wn = wday_name[timeptr->tm_wday];
93 if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR)
94 mn = "???";
95 else mn = mon_name[timeptr->tm_mon];
96 /*
97 ** Use strftime's %Y to generate the year, to avoid overflow problems
98 ** when computing timeptr->tm_year + TM_YEAR_BASE.
99 ** Assume that strftime is unaffected by other out-of-range members
100 ** (e.g., timeptr->tm_mday) when processing "%Y".
101 */
102 (void) strftime(year, sizeof year, "%Y", timeptr);
103 /*
104 ** We avoid using snprintf since it's not available on all systems.
105 */
106 (void) sprintf(result,
107 ((strlen(year) <= 4) ? ASCTIME_FMT : ASCTIME_FMT_B),
108 wn, mn,
109 timeptr->tm_mday, timeptr->tm_hour,
110 timeptr->tm_min, timeptr->tm_sec,
111 year);
112 if (strlen(result) < STD_ASCTIME_BUF_SIZE || buf == buf_asctime)
113 return strcpy(buf, result);
114 else {
115 #ifdef EOVERFLOW
116 errno = EOVERFLOW;
117 #else /* !defined EOVERFLOW */
118 errno = EINVAL;
119 #endif /* !defined EOVERFLOW */
120 return NULL;
121 }
122 }
123
124 /*
125 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
126 */
127
128 char *
asctime(register const struct tm * timeptr)129 asctime(register const struct tm *timeptr)
130 {
131 return asctime_r(timeptr, buf_asctime);
132 }
133