1 /* $OpenBSD: asctime.c,v 1.23 2015/10/24 18:13:18 guenther Exp $ */ 2 /* 3 ** This file is in the public domain, so clarified as of 4 ** 1996-06-05 by Arthur David Olson. 5 */ 6 7 /* 8 ** Avoid the temptation to punt entirely to strftime; 9 ** the output of strftime is supposed to be locale specific 10 ** whereas the output of asctime is supposed to be constant. 11 */ 12 13 #include <errno.h> 14 #include <stdio.h> 15 #include <string.h> 16 #include "private.h" 17 #include "tzfile.h" 18 #include "thread_private.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 #define ASCTIME_FMT "%.3s %.3s%3d %2.2d:%2.2d:%2.2d %-4s\n" 39 40 /* 41 ** For years that are more than four digits we put extra spaces before the year 42 ** so that code trying to overwrite the newline won't end up overwriting 43 ** a digit within a year and truncating the year (operating on the assumption 44 ** that no output is better than wrong output). 45 */ 46 #define ASCTIME_FMT_B "%.3s %.3s%3d %2.2d:%2.2d:%2.2d %s\n" 47 48 #define STD_ASCTIME_BUF_SIZE 26 49 /* 50 ** Big enough for something such as 51 ** ??? ???-2147483648 -2147483648:-2147483648:-2147483648 -2147483648\n 52 ** (two three-character abbreviations, five strings denoting integers, 53 ** seven explicit spaces, two explicit colons, a newline, 54 ** and a trailing ASCII nul). 55 ** The values above are for systems where an int is 32 bits and are provided 56 ** as an example; the define below calculates the maximum for the system at 57 ** hand. 58 */ 59 #define MAX_ASCTIME_BUF_SIZE (2*3+5*INT_STRLEN_MAXIMUM(int)+7+2+1+1) 60 61 static char * 62 asctime3(const struct tm *timeptr, char *buf, int bufsize) 63 { 64 static const char wday_name[][4] = { 65 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" 66 }; 67 static const char mon_name[][4] = { 68 "Jan", "Feb", "Mar", "Apr", "May", "Jun", 69 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" 70 }; 71 const char * wn; 72 const char * mn; 73 char year[INT_STRLEN_MAXIMUM(int) + 2]; 74 int len; 75 76 if (timeptr == NULL) { 77 errno = EINVAL; 78 strlcpy(buf, "??? ??? ?? ??:??:?? ????\n", bufsize); 79 return buf; 80 } 81 if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK) 82 wn = "???"; 83 else 84 wn = wday_name[timeptr->tm_wday]; 85 if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR) 86 mn = "???"; 87 else 88 mn = mon_name[timeptr->tm_mon]; 89 /* 90 ** Use strftime's %Y to generate the year, to avoid overflow problems 91 ** when computing timeptr->tm_year + TM_YEAR_BASE. 92 ** Assume that strftime is unaffected by other out-of-range members 93 ** (e.g., timeptr->tm_mday) when processing "%Y". 94 */ 95 (void) strftime(year, sizeof year, "%Y", timeptr); 96 len = snprintf(buf, bufsize, 97 ((strlen(year) <= 4) ? ASCTIME_FMT : ASCTIME_FMT_B), 98 wn, mn, 99 timeptr->tm_mday, timeptr->tm_hour, 100 timeptr->tm_min, timeptr->tm_sec, 101 year); 102 if (len != -1 && len < bufsize) { 103 return buf; 104 } else { 105 errno = EOVERFLOW; 106 return NULL; 107 } 108 } 109 110 /* 111 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition. 112 */ 113 114 char * 115 asctime_r(const struct tm *timeptr, char *buf) 116 { 117 /* 118 ** P1003 8.3.5.2 says that asctime_r() can only assume at most 119 ** a 26 byte buffer. 120 */ 121 return asctime3(timeptr, buf, STD_ASCTIME_BUF_SIZE); 122 } 123 DEF_WEAK(asctime_r); 124 125 /* 126 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition. 127 */ 128 129 char * 130 asctime(const struct tm *timeptr) 131 { 132 static char result[MAX_ASCTIME_BUF_SIZE]; 133 _THREAD_PRIVATE_KEY(asctime); 134 char *resultp = (char *)_THREAD_PRIVATE(asctime, result, NULL); 135 136 if (resultp == NULL) 137 return NULL; 138 else 139 return asctime3(timeptr, resultp, sizeof(result)); 140 } 141 DEF_STRONG(asctime); 142