debug/strncat_chk.c

   1 /* Copyright (C) 1991, 1997, 2004 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, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <string.h>
  20
  21 #include <memcopy.h>
  22
  23
  24 char *
  25 __strncat_chk (s1, s2, n, s1len)
  26      char *s1;
  27      const char *s2;
  28      size_t n;
  29      size_t s1len;
  30 {
  31   reg_char c;
  32   char *s = s1;
  33
  34   /* Find the end of S1.  */
  35   do
  36     {
  37       if (__builtin_expect (s1len-- == 0, 0))
  38         __chk_fail ();
  39       c = *s1++;
  40     }
  41   while (c != '\0');
  42
  43   /* Make S1 point before next character, so we can increment
  44      it while memory is read (wins on pipelined cpus).  */
  45   ++s1len;
  46   s1 -= 2;
  47
  48   if (n >= 4)
  49     {
  50       size_t n4 = n >> 2;
  51       do
  52         {
  53           if (__builtin_expect (s1len-- == 0, 0))
  54             __chk_fail ();
  55           c = *s2++;
  56           *++s1 = c;
  57           if (c == '\0')
  58             return s;
  59           if (__builtin_expect (s1len-- == 0, 0))
  60             __chk_fail ();
  61           c = *s2++;
  62           *++s1 = c;
  63           if (c == '\0')
  64             return s;
  65           if (__builtin_expect (s1len-- == 0, 0))
  66             __chk_fail ();
  67           c = *s2++;
  68           *++s1 = c;
  69           if (c == '\0')
  70             return s;
  71           if (__builtin_expect (s1len-- == 0, 0))
  72             __chk_fail ();
  73           c = *s2++;
  74           *++s1 = c;
  75           if (c == '\0')
  76             return s;
  77         } while (--n4 > 0);
  78       n &= 3;
  79     }
  80
  81   while (n > 0)
  82     {
  83       if (__builtin_expect (s1len-- == 0, 0))
  84         __chk_fail ();
  85       c = *s2++;
  86       *++s1 = c;
  87       if (c == '\0')
  88         return s;
  89       n--;
  90     }
  91
  92   if (c != '\0')
  93     {
  94       if (__builtin_expect (s1len-- == 0, 0))
  95         __chk_fail ();
  96       *++s1 = '\0';
  97     }
  98
  99   return s;
 100 }