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 ** $FreeBSD: head/contrib/tzcode/stdtime/asctime.c 214411 2010-10-27 07:14:46Z edwin $
12 */
13 /*LINTLIBRARY*/
14
15 #include "namespace.h"
16 #include "private.h"
17 #include "un-namespace.h"
18 #include "tzfile.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 #ifdef __GNUC__
39 #define ASCTIME_FMT "%.3s %.3s%3d %2.2d:%2.2d:%2.2d %-4s\n"
40 #else /* !defined __GNUC__ */
41 #define ASCTIME_FMT "%.3s %.3s%3d %02.2d:%02.2d:%02.2d %-4s\n"
42 #endif /* !defined __GNUC__ */
43 /*
44 ** For years that are more than four digits we put extra spaces before the year
45 ** so that code trying to overwrite the newline won't end up overwriting
46 ** a digit within a year and truncating the year (operating on the assumption
47 ** that no output is better than wrong output).
48 */
49 #ifdef __GNUC__
50 #define ASCTIME_FMT_B "%.3s %.3s%3d %2.2d:%2.2d:%2.2d %s\n"
51 #else /* !defined __GNUC__ */
52 #define ASCTIME_FMT_B "%.3s %.3s%3d %02.2d:%02.2d:%02.2d %s\n"
53 #endif /* !defined __GNUC__ */
54
55 #define STD_ASCTIME_BUF_SIZE 26
56 /*
57 ** Big enough for something such as
58 ** ??? ???-2147483648 -2147483648:-2147483648:-2147483648 -2147483648\n
59 ** (two three-character abbreviations, five strings denoting integers,
60 ** seven explicit spaces, two explicit colons, a newline,
61 ** and a trailing ASCII nul).
62 ** The values above are for systems where an int is 32 bits and are provided
63 ** as an example; the define below calculates the maximum for the system at
64 ** hand.
65 */
66 #define MAX_ASCTIME_BUF_SIZE (2*3+5*INT_STRLEN_MAXIMUM(int)+7+2+1+1)
67
68 static char buf_asctime[MAX_ASCTIME_BUF_SIZE];
69
70 /*
71 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
72 */
73
74 char *
asctime_r(const struct tm * __restrict timeptr,char * __restrict buf)75 asctime_r(const struct tm * __restrict timeptr, char * __restrict buf)
76 {
77 static const char wday_name[][3] = {
78 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
79 };
80 static const char mon_name[][3] = {
81 "Jan", "Feb", "Mar", "Apr", "May", "Jun",
82 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
83 };
84 char year[INT_STRLEN_MAXIMUM(int) + 2];
85 char result[MAX_ASCTIME_BUF_SIZE];
86 const char * wn;
87 const char * mn;
88
89 if (timeptr == NULL) {
90 errno = EINVAL;
91 return strcpy(buf, "??? ??? ?? ??:??:?? ????\n");
92 }
93 if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK)
94 wn = "???";
95 else wn = wday_name[timeptr->tm_wday];
96 if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR)
97 mn = "???";
98 else mn = mon_name[timeptr->tm_mon];
99 /*
100 ** Use strftime's %Y to generate the year, to avoid overflow problems
101 ** when computing timeptr->tm_year + TM_YEAR_BASE.
102 ** Assume that strftime is unaffected by other out-of-range members
103 ** (e.g., timeptr->tm_mday) when processing "%Y".
104 */
105 strftime(year, sizeof year, "%Y", timeptr);
106 snprintf(result, sizeof 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 errno = EOVERFLOW;
116 return NULL;
117 }
118 }
119
120 /*
121 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
122 */
123
124 char *
asctime(const struct tm * timeptr)125 asctime(const struct tm *timeptr)
126 {
127 return asctime_r(timeptr, buf_asctime);
128 }
129