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glibc  2.9
strncat_chk.c
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00001 /* Copyright (C) 1991, 1997, 2004 Free Software Foundation, Inc.
00002    This file is part of the GNU C Library.
00003 
00004    The GNU C Library is free software; you can redistribute it and/or
00005    modify it under the terms of the GNU Lesser General Public
00006    License as published by the Free Software Foundation; either
00007    version 2.1 of the License, or (at your option) any later version.
00008 
00009    The GNU C Library is distributed in the hope that it will be useful,
00010    but WITHOUT ANY WARRANTY; without even the implied warranty of
00011    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00012    Lesser General Public License for more details.
00013 
00014    You should have received a copy of the GNU Lesser General Public
00015    License along with the GNU C Library; if not, write to the Free
00016    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00017    02111-1307 USA.  */
00018 
00019 #include <string.h>
00020 
00021 #include <memcopy.h>
00022 
00023 
00024 char *
00025 __strncat_chk (s1, s2, n, s1len)
00026      char *s1;
00027      const char *s2;
00028      size_t n;
00029      size_t s1len;
00030 {
00031   reg_char c;
00032   char *s = s1;
00033 
00034   /* Find the end of S1.  */
00035   do
00036     {
00037       if (__builtin_expect (s1len-- == 0, 0))
00038        __chk_fail ();
00039       c = *s1++;
00040     }
00041   while (c != '\0');
00042 
00043   /* Make S1 point before next character, so we can increment
00044      it while memory is read (wins on pipelined cpus).  */
00045   ++s1len;
00046   s1 -= 2;
00047 
00048   if (n >= 4)
00049     {
00050       size_t n4 = n >> 2;
00051       do
00052        {
00053          if (__builtin_expect (s1len-- == 0, 0))
00054            __chk_fail ();
00055          c = *s2++;
00056          *++s1 = c;
00057          if (c == '\0')
00058            return s;
00059          if (__builtin_expect (s1len-- == 0, 0))
00060            __chk_fail ();
00061          c = *s2++;
00062          *++s1 = c;
00063          if (c == '\0')
00064            return s;
00065          if (__builtin_expect (s1len-- == 0, 0))
00066            __chk_fail ();
00067          c = *s2++;
00068          *++s1 = c;
00069          if (c == '\0')
00070            return s;
00071          if (__builtin_expect (s1len-- == 0, 0))
00072            __chk_fail ();
00073          c = *s2++;
00074          *++s1 = c;
00075          if (c == '\0')
00076            return s;
00077        } while (--n4 > 0);
00078       n &= 3;
00079     }
00080 
00081   while (n > 0)
00082     {
00083       if (__builtin_expect (s1len-- == 0, 0))
00084        __chk_fail ();
00085       c = *s2++;
00086       *++s1 = c;
00087       if (c == '\0')
00088        return s;
00089       n--;
00090     }
00091 
00092   if (c != '\0')
00093     {
00094       if (__builtin_expect (s1len-- == 0, 0))
00095        __chk_fail ();
00096       *++s1 = '\0';
00097     }
00098 
00099   return s;
00100 }