debug/strncpy_chk.c

   1 /* Copyright (C) 1991, 1997, 2003, 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 #include <memcopy.h>
  21
  22
  23 char *
  24 __strncpy_chk (s1, s2, n, s1len)
  25      char *s1;
  26      const char *s2;
  27      size_t n;
  28      size_t s1len;
  29 {
  30   reg_char c;
  31   char *s = s1;
  32
  33   if (__builtin_expect (s1len < n, 0))
  34     __chk_fail ();
  35
  36   --s1;
  37
  38   if (n >= 4)
  39     {
  40       size_t n4 = n >> 2;
  41
  42       for (;;)
  43         {
  44           c = *s2++;
  45           *++s1 = c;
  46           if (c == '\0')
  47             break;
  48           c = *s2++;
  49           *++s1 = c;
  50           if (c == '\0')
  51             break;
  52           c = *s2++;
  53           *++s1 = c;
  54           if (c == '\0')
  55             break;
  56           c = *s2++;
  57           *++s1 = c;
  58           if (c == '\0')
  59             break;
  60           if (--n4 == 0)
  61             goto last_chars;
  62         }
  63       n = n - (s1 - s) - 1;
  64       if (n == 0)
  65         return s;
  66       goto zero_fill;
  67     }
  68
  69  last_chars:
  70   n &= 3;
  71   if (n == 0)
  72     return s;
  73
  74   do
  75     {
  76       c = *s2++;
  77       *++s1 = c;
  78       if (--n == 0)
  79         return s;
  80     }
  81   while (c != '\0');
  82
  83  zero_fill:
  84   do
  85     *++s1 = '\0';
  86   while (--n > 0);
  87
  88   return s;
  89 }