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 #ifndef lint
13 #ifndef NOID
14 static char elsieid[] = "@(#)asctime.c 8.2";
15 #endif /* !defined NOID */
16 #endif /* !defined lint */
17
18 /*LINTLIBRARY*/
19
20 #include "private.h"
21 #include "tzfile.h"
22
23 /*
24 ** Some systems only handle "%.2d"; others only handle "%02d";
25 ** "%02.2d" makes (most) everybody happy.
26 ** At least some versions of gcc warn about the %02.2d;
27 ** we conditionalize below to avoid the warning.
28 */
29 /*
30 ** All years associated with 32-bit time_t values are exactly four digits long;
31 ** some years associated with 64-bit time_t values are not.
32 ** Vintage programs are coded for years that are always four digits long
33 ** and may assume that the newline always lands in the same place.
34 ** For years that are less than four digits, we pad the output with
35 ** leading zeroes to get the newline in the traditional place.
36 ** The -4 ensures that we get four characters of output even if
37 ** we call a strftime variant that produces fewer characters for some years.
38 ** The ISO C 1999 and POSIX 1003.1-2004 standards prohibit padding the year,
39 ** but many implementations pad anyway; most likely the standards are buggy.
40 */
41 #ifdef __GNUC__
42 #define ASCTIME_FMT "%.3s %.3s%3d %2.2d:%2.2d:%2.2d %-4s\n"
43 #else /* !defined __GNUC__ */
44 #define ASCTIME_FMT "%.3s %.3s%3d %02.2d:%02.2d:%02.2d %-4s\n"
45 #endif /* !defined __GNUC__ */
46 /*
47 ** For years that are more than four digits we put extra spaces before the year
48 ** so that code trying to overwrite the newline won't end up overwriting
49 ** a digit within a year and truncating the year (operating on the assumption
50 ** that no output is better than wrong output).
51 */
52 #ifdef __GNUC__
53 #define ASCTIME_FMT_B "%.3s %.3s%3d %2.2d:%2.2d:%2.2d %s\n"
54 #else /* !defined __GNUC__ */
55 #define ASCTIME_FMT_B "%.3s %.3s%3d %02.2d:%02.2d:%02.2d %s\n"
56 #endif /* !defined __GNUC__ */
57
58 #define STD_ASCTIME_BUF_SIZE 26
59 /*
60 ** Big enough for something such as
61 ** ??? ???-2147483648 -2147483648:-2147483648:-2147483648 -2147483648\n
62 ** (two three-character abbreviations, five strings denoting integers,
63 ** seven explicit spaces, two explicit colons, a newline,
64 ** and a trailing ASCII nul).
65 ** The values above are for systems where an int is 32 bits and are provided
66 ** as an example; the define below calculates the maximum for the system at
67 ** hand.
68 */
69 #define MAX_ASCTIME_BUF_SIZE (2*3+5*INT_STRLEN_MAXIMUM(int)+7+2+1+1)
70
71 static char buf_asctime[MAX_ASCTIME_BUF_SIZE];
72
73 /*
74 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
75 */
76
77 char *
asctime_r(timeptr,buf)78 asctime_r(timeptr, buf)
79 register const struct tm * timeptr;
80 char * buf;
81 {
82 static const char wday_name[][3] = {
83 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
84 };
85 static const char mon_name[][3] = {
86 "Jan", "Feb", "Mar", "Apr", "May", "Jun",
87 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
88 };
89 register const char * wn;
90 register const char * mn;
91 char year[INT_STRLEN_MAXIMUM(int) + 2];
92 char result[MAX_ASCTIME_BUF_SIZE];
93
94 if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK)
95 wn = "???";
96 else wn = wday_name[timeptr->tm_wday];
97 if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR)
98 mn = "???";
99 else mn = mon_name[timeptr->tm_mon];
100 /*
101 ** Use strftime's %Y to generate the year, to avoid overflow problems
102 ** when computing timeptr->tm_year + TM_YEAR_BASE.
103 ** Assume that strftime is unaffected by other out-of-range members
104 ** (e.g., timeptr->tm_mday) when processing "%Y".
105 */
106 (void) strftime(year, sizeof year, "%Y", timeptr);
107 /*
108 ** We avoid using snprintf since it's not available on all systems.
109 */
110 (void) sprintf(result,
111 ((strlen(year) <= 4) ? ASCTIME_FMT : ASCTIME_FMT_B),
112 wn, mn,
113 timeptr->tm_mday, timeptr->tm_hour,
114 timeptr->tm_min, timeptr->tm_sec,
115 year);
116 if (strlen(result) < STD_ASCTIME_BUF_SIZE || buf == buf_asctime) {
117 (void) strcpy(buf, result);
118 return buf;
119 } else {
120 #ifdef EOVERFLOW
121 errno = EOVERFLOW;
122 #else /* !defined EOVERFLOW */
123 errno = EINVAL;
124 #endif /* !defined EOVERFLOW */
125 return NULL;
126 }
127 }
128
129 /*
130 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
131 */
132
133 char *
asctime(timeptr)134 asctime(timeptr)
135 register const struct tm * timeptr;
136 {
137 return asctime_r(timeptr, buf_asctime);
138 }
139