1 /* $NetBSD: asctime.c,v 1.27 2019/01/27 02:40:49 dholland Exp $ */ 2 3 /* asctime and asctime_r a la POSIX and ISO C, except pad years before 1000. */ 4 5 /* 6 ** This file is in the public domain, so clarified as of 7 ** 1996-06-05 by Arthur David Olson. 8 */ 9 10 /* 11 ** Avoid the temptation to punt entirely to strftime; 12 ** the output of strftime is supposed to be locale specific 13 ** whereas the output of asctime is supposed to be constant. 14 */ 15 16 #include <sys/cdefs.h> 17 #if defined(LIBC_SCCS) && !defined(lint) 18 #if 0 19 static char elsieid[] = "@(#)asctime.c 8.5"; 20 #else 21 __RCSID("$NetBSD: asctime.c,v 1.27 2019/01/27 02:40:49 dholland Exp $"); 22 #endif 23 #endif /* LIBC_SCCS and not lint */ 24 25 /*LINTLIBRARY*/ 26 27 #include "namespace.h" 28 #include "private.h" 29 #include <stdio.h> 30 31 #ifdef __weak_alias 32 __weak_alias(asctime_r,_asctime_r) 33 #endif 34 35 /* 36 ** Some systems only handle "%.2d"; others only handle "%02d"; 37 ** "%02.2d" makes (most) everybody happy. 38 ** At least some versions of gcc warn about the %02.2d; 39 ** we conditionalize below to avoid the warning. 40 */ 41 /* 42 ** All years associated with 32-bit time_t values are exactly four digits long; 43 ** some years associated with 64-bit time_t values are not. 44 ** Vintage programs are coded for years that are always four digits long 45 ** and may assume that the newline always lands in the same place. 46 ** For years that are less than four digits, we pad the output with 47 ** leading zeroes to get the newline in the traditional place. 48 ** The -4 ensures that we get four characters of output even if 49 ** we call a strftime variant that produces fewer characters for some years. 50 ** The ISO C and POSIX standards prohibit padding the year, 51 ** but many implementations pad anyway; most likely the standards are buggy. 52 */ 53 #ifdef __GNUC__ 54 #define ASCTIME_FMT "%s %s%3d %2.2d:%2.2d:%2.2d %-4s\n" 55 #else /* !defined __GNUC__ */ 56 #define ASCTIME_FMT "%s %s%3d %02.2d:%02.2d:%02.2d %-4s\n" 57 #endif /* !defined __GNUC__ */ 58 /* 59 ** For years that are more than four digits we put extra spaces before the year 60 ** so that code trying to overwrite the newline won't end up overwriting 61 ** a digit within a year and truncating the year (operating on the assumption 62 ** that no output is better than wrong output). 63 */ 64 #ifdef __GNUC__ 65 #define ASCTIME_FMT_B "%s %s%3d %2.2d:%2.2d:%2.2d %s\n" 66 #else /* !defined __GNUC__ */ 67 #define ASCTIME_FMT_B "%s %s%3d %02.2d:%02.2d:%02.2d %s\n" 68 #endif /* !defined __GNUC__ */ 69 70 #define STD_ASCTIME_BUF_SIZE 26 71 /* 72 ** Big enough for something such as 73 ** ??? ???-2147483648 -2147483648:-2147483648:-2147483648 -2147483648\n 74 ** (two three-character abbreviations, five strings denoting integers, 75 ** seven explicit spaces, two explicit colons, a newline, 76 ** and a trailing NUL byte). 77 ** The values above are for systems where an int is 32 bits and are provided 78 ** as an example; the define below calculates the maximum for the system at 79 ** hand. 80 */ 81 #define MAX_ASCTIME_BUF_SIZE (2*3+5*INT_STRLEN_MAXIMUM(int)+7+2+1+1) 82 83 static char buf_asctime[MAX_ASCTIME_BUF_SIZE]; 84 85 char * 86 asctime_r(const struct tm *timeptr, char *buf) 87 { 88 static const char wday_name[][4] = { 89 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" 90 }; 91 static const char mon_name[][4] = { 92 "Jan", "Feb", "Mar", "Apr", "May", "Jun", 93 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" 94 }; 95 const char * wn; 96 const char * mn; 97 char year[INT_STRLEN_MAXIMUM(int) + 2]; 98 char result[MAX_ASCTIME_BUF_SIZE]; 99 100 if (timeptr == NULL) { 101 errno = EINVAL; 102 return strcpy(buf, "??? ??? ?? ??:??:?? ????\n"); 103 } 104 if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK) 105 wn = "???"; 106 else wn = wday_name[timeptr->tm_wday]; 107 if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR) 108 mn = "???"; 109 else mn = mon_name[timeptr->tm_mon]; 110 /* 111 ** Use strftime's %Y to generate the year, to avoid overflow problems 112 ** when computing timeptr->tm_year + TM_YEAR_BASE. 113 ** Assume that strftime is unaffected by other out-of-range members 114 ** (e.g., timeptr->tm_mday) when processing "%Y". 115 */ 116 (void) strftime(year, sizeof year, "%Y", timeptr); 117 (void) snprintf(result, 118 sizeof(result), 119 ((strlen(year) <= 4) ? ASCTIME_FMT : ASCTIME_FMT_B), 120 wn, mn, 121 timeptr->tm_mday, timeptr->tm_hour, 122 timeptr->tm_min, timeptr->tm_sec, 123 year); 124 if (strlen(result) < STD_ASCTIME_BUF_SIZE || buf == buf_asctime) 125 return strcpy(buf, result); 126 else { 127 errno = EOVERFLOW; 128 return NULL; 129 } 130 } 131 132 char * 133 asctime(const struct tm *timeptr) 134 { 135 return asctime_r(timeptr, buf_asctime); 136 } 137