asctime.c revision c73f511526464f8e56c242df80552e9b0d94ae3d 
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#ifndef lint
13#ifndef NOID
14static char	elsieid[] = "@(#)asctime.c	8.2";
15#endif /* !defined NOID */
16#endif /* !defined lint */
17
18/*LINTLIBRARY*/
19
20#include "private.h"
21#include "tzfile.h"
22
23/*
24** Some systems only handle "%.2d"; others only handle "%02d";
25** "%02.2d" makes (most) everybody happy.
26** At least some versions of gcc warn about the %02.2d;
27** we conditionalize below to avoid the warning.
28*/
29/*
30** All years associated with 32-bit time_t values are exactly four digits long;
31** some years associated with 64-bit time_t values are not.
32** Vintage programs are coded for years that are always four digits long
33** and may assume that the newline always lands in the same place.
34** For years that are less than four digits, we pad the output with
35** leading zeroes to get the newline in the traditional place.
36** The -4 ensures that we get four characters of output even if
37** we call a strftime variant that produces fewer characters for some years.
38** The ISO C 1999 and POSIX 1003.1-2004 standards prohibit padding the year,
39** but many implementations pad anyway; most likely the standards are buggy.
40*/
41#ifdef __GNUC__
42#define ASCTIME_FMT	"%.3s %.3s%3d %2.2d:%2.2d:%2.2d %-4s\n"
43#else /* !defined __GNUC__ */
44#define ASCTIME_FMT	"%.3s %.3s%3d %02.2d:%02.2d:%02.2d %-4s\n"
45#endif /* !defined __GNUC__ */
46/*
47** For years that are more than four digits we put extra spaces before the year
48** so that code trying to overwrite the newline won't end up overwriting
49** a digit within a year and truncating the year (operating on the assumption
50** that no output is better than wrong output).
51*/
52#ifdef __GNUC__
53#define ASCTIME_FMT_B	"%.3s %.3s%3d %2.2d:%2.2d:%2.2d     %s\n"
54#else /* !defined __GNUC__ */
55#define ASCTIME_FMT_B	"%.3s %.3s%3d %02.2d:%02.2d:%02.2d     %s\n"
56#endif /* !defined __GNUC__ */
57
58#define STD_ASCTIME_BUF_SIZE	26
59/*
60** Big enough for something such as
61** ??? ???-2147483648 -2147483648:-2147483648:-2147483648     -2147483648\n
62** (two three-character abbreviations, five strings denoting integers,
63** seven explicit spaces, two explicit colons, a newline,
64** and a trailing ASCII nul).
65** The values above are for systems where an int is 32 bits and are provided
66** as an example; the define below calculates the maximum for the system at
67** hand.
68*/
69#define MAX_ASCTIME_BUF_SIZE	(2*3+5*INT_STRLEN_MAXIMUM(int)+7+2+1+1)
70
71static char	buf_asctime[MAX_ASCTIME_BUF_SIZE];
72
73/*
74** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
75*/
76
77char *
78asctime_r(timeptr, buf)
79register const struct tm *	timeptr;
80char *				buf;
81{
82	static const char	wday_name[][3] = {
83		"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
84	};
85	static const char	mon_name[][3] = {
86		"Jan", "Feb", "Mar", "Apr", "May", "Jun",
87		"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
88	};
89	register const char *	wn;
90	register const char *	mn;
91	char			year[INT_STRLEN_MAXIMUM(int) + 2];
92	char			result[MAX_ASCTIME_BUF_SIZE];
93
94	if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK)
95		wn = "???";
96	else	wn = wday_name[timeptr->tm_wday];
97	if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR)
98		mn = "???";
99	else	mn = mon_name[timeptr->tm_mon];
100	/*
101	** Use strftime's %Y to generate the year, to avoid overflow problems
102	** when computing timeptr->tm_year + TM_YEAR_BASE.
103	** Assume that strftime is unaffected by other out-of-range members
104	** (e.g., timeptr->tm_mday) when processing "%Y".
105	*/
106	(void) strftime(year, sizeof year, "%Y", timeptr);
107	/*
108	** We avoid using snprintf since it's not available on all systems.
109	*/
110	(void) sprintf(result,
111		((strlen(year) <= 4) ? ASCTIME_FMT : ASCTIME_FMT_B),
112		wn, mn,
113		timeptr->tm_mday, timeptr->tm_hour,
114		timeptr->tm_min, timeptr->tm_sec,
115		year);
116	if (strlen(result) < STD_ASCTIME_BUF_SIZE || buf == buf_asctime) {
117		(void) strcpy(buf, result);
118		return buf;
119	} else {
120#ifdef EOVERFLOW
121		errno = EOVERFLOW;
122#else /* !defined EOVERFLOW */
123		errno = EINVAL;
124#endif /* !defined EOVERFLOW */
125		return NULL;
126	}
127}
128
129/*
130** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
131*/
132
133char *
134asctime(timeptr)
135register const struct tm *	timeptr;
136{
137	return asctime_r(timeptr, buf_asctime);
138}
139