glibc/time/asctime.c

90 lines
2.9 KiB
C

/* Copyright (C) 1991-2023 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include "../locale/localeinfo.h"
#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <time.h>
/* This is defined in locale/C-time.c in the GNU libc. */
extern const struct __locale_data _nl_C_LC_TIME attribute_hidden;
#define ab_day_name(DAY) (_nl_C_LC_TIME.values[_NL_ITEM_INDEX (ABDAY_1)+(DAY)].string)
#define ab_month_name(MON) (_nl_C_LC_TIME.values[_NL_ITEM_INDEX (ABMON_1)+(MON)].string)
static const char format[] = "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n";
static char result[ 3+1+ 3+1+20+1+20+1+20+1+20+1+20+1 + 1];
static char *
asctime_internal (const struct tm *tp, char *buf, size_t buflen)
{
if (tp == NULL)
{
__set_errno (EINVAL);
return NULL;
}
/* We limit the size of the year which can be printed. Using the %d
format specifier used the addition of 1900 would overflow the
number and a negative vaue is printed. For some architectures we
could in theory use %ld or an evern larger integer format but
this would mean the output needs more space. This would not be a
problem if the 'asctime_r' interface would be defined sanely and
a buffer size would be passed. */
if (__glibc_unlikely (tp->tm_year > INT_MAX - 1900))
{
eoverflow:
__set_errno (EOVERFLOW);
return NULL;
}
int n = __snprintf (buf, buflen, format,
(tp->tm_wday < 0 || tp->tm_wday >= 7
? "???" : ab_day_name (tp->tm_wday)),
(tp->tm_mon < 0 || tp->tm_mon >= 12
? "???" : ab_month_name (tp->tm_mon)),
tp->tm_mday, tp->tm_hour, tp->tm_min,
tp->tm_sec, 1900 + tp->tm_year);
if (n < 0)
return NULL;
if (n >= buflen)
goto eoverflow;
return buf;
}
/* Like asctime, but write result to the user supplied buffer. The
buffer is only guaranteed to be 26 bytes in length. */
char *
__asctime_r (const struct tm *tp, char *buf)
{
return asctime_internal (tp, buf, 26);
}
weak_alias (__asctime_r, asctime_r)
/* Returns a string of the form "Day Mon dd hh:mm:ss yyyy\n"
which is the representation of TP in that form. */
char *
asctime (const struct tm *tp)
{
return asctime_internal (tp, result, sizeof (result));
}
libc_hidden_def (asctime)