1 /* asctime and asctime_r a la POSIX and ISO C, except pad years before 1000. */
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 /*LINTLIBRARY*/
15
16 #include "private.h"
17 #include <stdio.h>
18
19 /*
20 ** Some systems only handle "%.2d"; others only handle "%02d";
21 ** "%02.2d" makes (most) everybody happy.
22 ** At least some versions of gcc warn about the %02.2d;
23 ** we conditionalize below to avoid the warning.
24 */
25 /*
26 ** All years associated with 32-bit time_t values are exactly four digits long;
27 ** some years associated with 64-bit time_t values are not.
28 ** Vintage programs are coded for years that are always four digits long
29 ** and may assume that the newline always lands in the same place.
30 ** For years that are less than four digits, we pad the output with
31 ** leading zeroes to get the newline in the traditional place.
32 ** The -4 ensures that we get four characters of output even if
33 ** we call a strftime variant that produces fewer characters for some years.
34 ** The ISO C and POSIX standards prohibit padding the year,
35 ** but many implementations pad anyway; most likely the standards are buggy.
36 */
37 #ifdef __GNUC__
38 #define ASCTIME_FMT "%s %s%3d %2.2d:%2.2d:%2.2d %-4s\n"
39 #else /* !defined __GNUC__ */
40 #define ASCTIME_FMT "%s %s%3d %02.2d:%02.2d:%02.2d %-4s\n"
41 #endif /* !defined __GNUC__ */
42 /*
43 ** For years that are more than four digits we put extra spaces before the year
44 ** so that code trying to overwrite the newline won't end up overwriting
45 ** a digit within a year and truncating the year (operating on the assumption
46 ** that no output is better than wrong output).
47 */
48 #ifdef __GNUC__
49 #define ASCTIME_FMT_B "%s %s%3d %2.2d:%2.2d:%2.2d %s\n"
50 #else /* !defined __GNUC__ */
51 #define ASCTIME_FMT_B "%s %s%3d %02.2d:%02.2d:%02.2d %s\n"
52 #endif /* !defined __GNUC__ */
53
54 #define STD_ASCTIME_BUF_SIZE 26
55 /*
56 ** Big enough for something such as
57 ** ??? ???-2147483648 -2147483648:-2147483648:-2147483648 -2147483648\n
58 ** (two three-character abbreviations, five strings denoting integers,
59 ** seven explicit spaces, two explicit colons, a newline,
60 ** and a trailing NUL byte).
61 ** The values above are for systems where an int is 32 bits and are provided
62 ** as an example; the define below calculates the maximum for the system at
63 ** hand.
64 */
65 #define MAX_ASCTIME_BUF_SIZE (2*3+5*INT_STRLEN_MAXIMUM(int)+7+2+1+1)
66
67 static char buf_asctime[MAX_ASCTIME_BUF_SIZE];
68
69 char *
asctime_r(register const struct tm * timeptr,char * buf)70 asctime_r(register const struct tm *timeptr, char *buf)
71 {
72 static const char wday_name[][4] = {
73 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
74 };
75 static const char mon_name[][4] = {
76 "Jan", "Feb", "Mar", "Apr", "May", "Jun",
77 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
78 };
79 register const char * wn;
80 register const char * mn;
81 char year[INT_STRLEN_MAXIMUM(int) + 2];
82 char result[MAX_ASCTIME_BUF_SIZE];
83
84 if (timeptr == NULL) {
85 errno = EINVAL;
86 return strcpy(buf, "??? ??? ?? ??:??:?? ????\n");
87 }
88 if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK)
89 wn = "???";
90 else wn = wday_name[timeptr->tm_wday];
91 if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR)
92 mn = "???";
93 else mn = mon_name[timeptr->tm_mon];
94 /*
95 ** Use strftime's %Y to generate the year, to avoid overflow problems
96 ** when computing timeptr->tm_year + TM_YEAR_BASE.
97 ** Assume that strftime is unaffected by other out-of-range members
98 ** (e.g., timeptr->tm_mday) when processing "%Y".
99 */
100 strftime(year, sizeof year, "%Y", timeptr);
101 /*
102 ** We avoid using snprintf since it's not available on all systems.
103 */
104 sprintf(result,
105 ((strlen(year) <= 4) ? ASCTIME_FMT : ASCTIME_FMT_B),
106 wn, mn,
107 timeptr->tm_mday, timeptr->tm_hour,
108 timeptr->tm_min, timeptr->tm_sec,
109 year);
110 if (strlen(result) < STD_ASCTIME_BUF_SIZE || buf == buf_asctime)
111 return strcpy(buf, result);
112 else {
113 errno = EOVERFLOW;
114 return NULL;
115 }
116 }
117
118 char *
asctime(register const struct tm * timeptr)119 asctime(register const struct tm *timeptr)
120 {
121 return asctime_r(timeptr, buf_asctime);
122 }
123