asctime.c (4324B)
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 12 /*LINTLIBRARY*/ 13 14 #include "private.h" 15 #include "tzfile.h" 16 17 /* 18 ** Some systems only handle "%.2d"; others only handle "%02d"; 19 ** "%02.2d" makes (most) everybody happy. 20 ** At least some versions of gcc warn about the %02.2d; 21 ** we conditionalize below to avoid the warning. 22 */ 23 /* 24 ** All years associated with 32-bit time_t values are exactly four digits long; 25 ** some years associated with 64-bit time_t values are not. 26 ** Vintage programs are coded for years that are always four digits long 27 ** and may assume that the newline always lands in the same place. 28 ** For years that are less than four digits, we pad the output with 29 ** leading zeroes to get the newline in the traditional place. 30 ** The -4 ensures that we get four characters of output even if 31 ** we call a strftime variant that produces fewer characters for some years. 32 ** The ISO C 1999 and POSIX 1003.1-2004 standards prohibit padding the year, 33 ** but many implementations pad anyway; most likely the standards are buggy. 34 */ 35 #ifdef __GNUC__ 36 #define ASCTIME_FMT "%.3s %.3s%3d %2.2d:%2.2d:%2.2d %-4s\n" 37 #else /* !defined __GNUC__ */ 38 #define ASCTIME_FMT "%.3s %.3s%3d %02.2d:%02.2d:%02.2d %-4s\n" 39 #endif /* !defined __GNUC__ */ 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 #ifdef __GNUC__ 47 #define ASCTIME_FMT_B "%.3s %.3s%3d %2.2d:%2.2d:%2.2d %s\n" 48 #else /* !defined __GNUC__ */ 49 #define ASCTIME_FMT_B "%.3s %.3s%3d %02.2d:%02.2d:%02.2d %s\n" 50 #endif /* !defined __GNUC__ */ 51 52 #define STD_ASCTIME_BUF_SIZE 26 53 /* 54 ** Big enough for something such as 55 ** ??? ???-2147483648 -2147483648:-2147483648:-2147483648 -2147483648\n 56 ** (two three-character abbreviations, five strings denoting integers, 57 ** seven explicit spaces, two explicit colons, a newline, 58 ** and a trailing ASCII nul). 59 ** The values above are for systems where an int is 32 bits and are provided 60 ** as an example; the define below calculates the maximum for the system at 61 ** hand. 62 */ 63 #define MAX_ASCTIME_BUF_SIZE (2*3+5*INT_STRLEN_MAXIMUM(int)+7+2+1+1) 64 65 static char buf_asctime[MAX_ASCTIME_BUF_SIZE]; 66 67 /* 68 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition. 69 */ 70 71 char * 72 asctime_r(register const struct tm *timeptr, char *buf) 73 { 74 static const char wday_name[][3] = { 75 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" 76 }; 77 static const char mon_name[][3] = { 78 "Jan", "Feb", "Mar", "Apr", "May", "Jun", 79 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" 80 }; 81 register const char * wn; 82 register const char * mn; 83 char year[INT_STRLEN_MAXIMUM(int) + 2]; 84 char result[MAX_ASCTIME_BUF_SIZE]; 85 86 if (timeptr == NULL) { 87 errno = EINVAL; 88 return strcpy(buf, "??? ??? ?? ??:??:?? ????\n"); 89 } 90 if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK) 91 wn = "???"; 92 else wn = wday_name[timeptr->tm_wday]; 93 if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR) 94 mn = "???"; 95 else mn = mon_name[timeptr->tm_mon]; 96 /* 97 ** Use strftime's %Y to generate the year, to avoid overflow problems 98 ** when computing timeptr->tm_year + TM_YEAR_BASE. 99 ** Assume that strftime is unaffected by other out-of-range members 100 ** (e.g., timeptr->tm_mday) when processing "%Y". 101 */ 102 (void) strftime(year, sizeof year, "%Y", timeptr); 103 /* 104 ** We avoid using snprintf since it's not available on all systems. 105 */ 106 (void) sprintf(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 #ifdef EOVERFLOW 116 errno = EOVERFLOW; 117 #else /* !defined EOVERFLOW */ 118 errno = EINVAL; 119 #endif /* !defined EOVERFLOW */ 120 return NULL; 121 } 122 } 123 124 /* 125 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition. 126 */ 127 128 char * 129 asctime(register const struct tm *timeptr) 130 { 131 return asctime_r(timeptr, buf_asctime); 132 }