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 "namespace.h" 17 #include "private.h" 18 #include "un-namespace.h" 19 #include <stdio.h> 20 21 /* 22 ** All years associated with 32-bit time_t values are exactly four digits long; 23 ** some years associated with 64-bit time_t values are not. 24 ** Vintage programs are coded for years that are always four digits long 25 ** and may assume that the newline always lands in the same place. 26 ** For years that are less than four digits, we pad the output with 27 ** leading zeroes to get the newline in the traditional place. 28 ** The -4 ensures that we get four characters of output even if 29 ** we call a strftime variant that produces fewer characters for some years. 30 ** The ISO C and POSIX standards prohibit padding the year, 31 ** but many implementations pad anyway; most likely the standards are buggy. 32 */ 33 static char const ASCTIME_FMT[] = "%s %s%3d %.2d:%.2d:%.2d %-4s\n"; 34 /* 35 ** For years that are more than four digits we put extra spaces before the year 36 ** so that code trying to overwrite the newline won't end up overwriting 37 ** a digit within a year and truncating the year (operating on the assumption 38 ** that no output is better than wrong output). 39 */ 40 static char const ASCTIME_FMT_B[] = "%s %s%3d %.2d:%.2d:%.2d %s\n"; 41 42 enum { STD_ASCTIME_BUF_SIZE = 26 }; 43 /* 44 ** Big enough for something such as 45 ** ??? ???-2147483648 -2147483648:-2147483648:-2147483648 -2147483648\n 46 ** (two three-character abbreviations, five strings denoting integers, 47 ** seven explicit spaces, two explicit colons, a newline, 48 ** and a trailing NUL byte). 49 ** The values above are for systems where an int is 32 bits and are provided 50 ** as an example; the size expression below is a bound for the system at 51 ** hand. 52 */ 53 static char buf_asctime[2*3 + 5*INT_STRLEN_MAXIMUM(int) + 7 + 2 + 1 + 1]; 54 55 /* A similar buffer for ctime. 56 C89 requires that they be the same buffer. 57 This requirement was removed in C99, so support it only if requested, 58 as support is more likely to lead to bugs in badly written programs. */ 59 #if SUPPORT_C89 60 # define buf_ctime buf_asctime 61 #else 62 static char buf_ctime[sizeof buf_asctime]; 63 #endif 64 65 char * 66 asctime_r(struct tm const *restrict timeptr, char *restrict buf) 67 { 68 static const char wday_name[][4] = { 69 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" 70 }; 71 static const char mon_name[][4] = { 72 "Jan", "Feb", "Mar", "Apr", "May", "Jun", 73 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" 74 }; 75 const char * wn; 76 const char * mn; 77 char year[INT_STRLEN_MAXIMUM(int) + 2]; 78 char result[sizeof buf_asctime]; 79 80 if (timeptr == NULL) { 81 errno = EINVAL; 82 return strcpy(buf, "??? ??? ?? ??:??:?? ????\n"); 83 } 84 if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK) 85 wn = "???"; 86 else wn = wday_name[timeptr->tm_wday]; 87 if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR) 88 mn = "???"; 89 else mn = mon_name[timeptr->tm_mon]; 90 /* 91 ** Use strftime's %Y to generate the year, to avoid overflow problems 92 ** when computing timeptr->tm_year + TM_YEAR_BASE. 93 ** Assume that strftime is unaffected by other out-of-range members 94 ** (e.g., timeptr->tm_mday) when processing "%Y". 95 */ 96 strftime(year, sizeof year, "%Y", timeptr); 97 /* 98 ** We avoid using snprintf since it's not available on all systems. 99 */ 100 sprintf(result, 101 ((strlen(year) <= 4) ? ASCTIME_FMT : ASCTIME_FMT_B), 102 wn, mn, 103 timeptr->tm_mday, timeptr->tm_hour, 104 timeptr->tm_min, timeptr->tm_sec, 105 year); 106 if (strlen(result) < STD_ASCTIME_BUF_SIZE 107 || buf == buf_ctime || buf == buf_asctime) 108 return strcpy(buf, result); 109 else { 110 errno = EOVERFLOW; 111 return NULL; 112 } 113 } 114 115 char * 116 asctime(register const struct tm *timeptr) 117 { 118 return asctime_r(timeptr, buf_asctime); 119 } 120 121 char * 122 ctime_r(const time_t *timep, char *buf) 123 { 124 struct tm mytm; 125 struct tm *tmp = localtime_r(timep, &mytm); 126 return tmp ? asctime_r(tmp, buf) : NULL; 127 } 128 129 char * 130 ctime(const time_t *timep) 131 { 132 return ctime_r(timep, buf_ctime); 133 } 134