debug/strncpy_chk.c

   1 /* Copyright (C) 1991-2013 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    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <string.h>
  19 #include <memcopy.h>
  20
  21
  22 char *
  23 __strncpy_chk (s1, s2, n, s1len)
  24      char *s1;
  25      const char *s2;
  26      size_t n;
  27      size_t s1len;
  28 {
  29   char c;
  30   char *s = s1;
  31
  32   if (__builtin_expect (s1len < n, 0))
  33     __chk_fail ();
  34
  35   --s1;
  36
  37   if (n >= 4)
  38     {
  39       size_t n4 = n >> 2;
  40
  41       for (;;)
  42         {
  43           c = *s2++;
  44           *++s1 = c;
  45           if (c == '\0')
  46             break;
  47           c = *s2++;
  48           *++s1 = c;
  49           if (c == '\0')
  50             break;
  51           c = *s2++;
  52           *++s1 = c;
  53           if (c == '\0')
  54             break;
  55           c = *s2++;
  56           *++s1 = c;
  57           if (c == '\0')
  58             break;
  59           if (--n4 == 0)
  60             goto last_chars;
  61         }
  62       n = n - (s1 - s) - 1;
  63       if (n == 0)
  64         return s;
  65       goto zero_fill;
  66     }
  67
  68  last_chars:
  69   n &= 3;
  70   if (n == 0)
  71     return s;
  72
  73   do
  74     {
  75       c = *s2++;
  76       *++s1 = c;
  77       if (--n == 0)
  78         return s;
  79     }
  80   while (c != '\0');
  81
  82  zero_fill:
  83   do
  84     *++s1 = '\0';
  85   while (--n > 0);
  86
  87   return s;
  88 }