1/* Copyright (C) 1991-2024 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18#include "../locale/localeinfo.h"
19#include <errno.h>
20#include <limits.h>
21#include <stdio.h>
22#include <time.h>
23
24/* This is defined in locale/C-time.c in the GNU libc. */
25extern const struct __locale_data _nl_C_LC_TIME attribute_hidden;
26#define ab_day_name(DAY) (_nl_C_LC_TIME.values[_NL_ITEM_INDEX (ABDAY_1)+(DAY)].string)
27#define ab_month_name(MON) (_nl_C_LC_TIME.values[_NL_ITEM_INDEX (ABMON_1)+(MON)].string)
28
29static const char format[] = "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n";
30static char result[ 3+1+ 3+1+20+1+20+1+20+1+20+1+20+1 + 1];
31
32
33static char *
34asctime_internal (const struct tm *tp, char *buf, size_t buflen)
35{
36 if (tp == NULL)
37 {
38 __set_errno (EINVAL);
39 return NULL;
40 }
41
42 /* We limit the size of the year which can be printed. Using the %d
43 format specifier used the addition of 1900 would overflow the
44 number and a negative value is printed. For some architectures we
45 could in theory use %ld or an evern larger integer format but
46 this would mean the output needs more space. This would not be a
47 problem if the 'asctime_r' interface would be defined sanely and
48 a buffer size would be passed. */
49 if (__glibc_unlikely (tp->tm_year > INT_MAX - 1900))
50 {
51 eoverflow:
52 __set_errno (EOVERFLOW);
53 return NULL;
54 }
55
56 int n = __snprintf (buf, buflen, format,
57 (tp->tm_wday < 0 || tp->tm_wday >= 7
58 ? "???" : ab_day_name (tp->tm_wday)),
59 (tp->tm_mon < 0 || tp->tm_mon >= 12
60 ? "???" : ab_month_name (tp->tm_mon)),
61 tp->tm_mday, tp->tm_hour, tp->tm_min,
62 tp->tm_sec, 1900 + tp->tm_year);
63 if (n < 0)
64 return NULL;
65 if (n >= buflen)
66 goto eoverflow;
67
68 return buf;
69}
70
71
72/* Like asctime, but write result to the user supplied buffer. The
73 buffer is only guaranteed to be 26 bytes in length. */
74char *
75__asctime_r (const struct tm *tp, char *buf)
76{
77 return asctime_internal (tp, buf, buflen: 26);
78}
79weak_alias (__asctime_r, asctime_r)
80
81
82/* Returns a string of the form "Day Mon dd hh:mm:ss yyyy\n"
83 which is the representation of TP in that form. */
84char *
85asctime (const struct tm *tp)
86{
87 return asctime_internal (tp, buf: result, buflen: sizeof (result));
88}
89libc_hidden_def (asctime)
90

source code of glibc/time/asctime.c