time/asctime.c

   1 /* Copyright (C) 1991,1993,1995-1997,2000,2002,2005,2010
   2    Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include "../locale/localeinfo.h"
  20 #include <errno.h>
  21 #include <limits.h>
  22 #include <stdio.h>
  23 #include <time.h>
  24
  25 /* This is defined in locale/C-time.c in the GNU libc.  */
  26 extern const struct __locale_data _nl_C_LC_TIME attribute_hidden;
  27 #define ab_day_name(DAY) (_nl_C_LC_TIME.values[_NL_ITEM_INDEX (ABDAY_1)+(DAY)].string)
  28 #define ab_month_name(MON) (_nl_C_LC_TIME.values[_NL_ITEM_INDEX (ABMON_1)+(MON)].string)
  29
  30 static const char format[] = "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n";
  31 static char result[              3+1+ 3+1+20+1+20+1+20+1+20+1+20+1 + 1];
  32
  33
  34 static char *
  35 asctime_internal (const struct tm *tp, char *buf, size_t buflen)
  36 {
  37   if (tp == NULL)
  38     {
  39       __set_errno (EINVAL);
  40       return NULL;
  41     }
  42
  43   /* We limit the size of the year which can be printed.  Using the %d
  44      format specifier used the addition of 1900 would overflow the
  45      number and a negative vaue is printed.  For some architectures we
  46      could in theory use %ld or an evern larger integer format but
  47      this would mean the output needs more space.  This would not be a
  48      problem if the 'asctime_r' interface would be defined sanely and
  49      a buffer size would be passed.  */
  50   if (__builtin_expect (tp->tm_year > INT_MAX - 1900, 0))
  51     {
  52     eoverflow:
  53       __set_errno (EOVERFLOW);
  54       return NULL;
  55     }
  56
  57   int n = __snprintf (buf, buflen, format,
  58                       (tp->tm_wday < 0 || tp->tm_wday >= 7 ?
  59                        "???" : ab_day_name (tp->tm_wday)),
  60                       (tp->tm_mon < 0 || tp->tm_mon >= 12 ?
  61                        "???" : ab_month_name (tp->tm_mon)),
  62                       tp->tm_mday, tp->tm_hour, tp->tm_min,
  63                       tp->tm_sec, 1900 + tp->tm_year);
  64   if (n < 0)
  65     return NULL;
  66   if (n >= buflen)
  67     goto eoverflow;
  68
  69   return buf;
  70 }
  71
  72
  73 /* Like asctime, but write result to the user supplied buffer.  The
  74    buffer is only guaranteed to be 26 bytes in length.  */
  75 char *
  76 __asctime_r (const struct tm *tp, char *buf)
  77 {
  78   return asctime_internal (tp, buf, 26);
  79 }
  80 weak_alias (__asctime_r, asctime_r)
  81
  82
  83 /* Returns a string of the form "Day Mon dd hh:mm:ss yyyy\n"
  84    which is the representation of TP in that form.  */
  85 char *
  86 asctime (const struct tm *tp)
  87 {
  88   return asctime_internal (tp, result, sizeof (result));
  89 }
  90 libc_hidden_def (asctime)