debug/wcsncat_chk.c

   1 /* Copyright (C) 1995-2017 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu>, 1995.
   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 <wchar.h>
  20
  21
  22 /* Append no more than N wide-character of SRC onto DEST.  */
  23 wchar_t *
  24 __wcsncat_chk (wchar_t *dest, const wchar_t *src, size_t n, size_t destlen)
  25 {
  26   wchar_t c;
  27   wchar_t * const s = dest;
  28
  29   /* Find the end of DEST.  */
  30   do
  31     {
  32       if (__glibc_unlikely (destlen-- == 0))
  33         __chk_fail ();
  34       c = *dest++;
  35     }
  36   while (c != L'\0');
  37
  38   /* Make DEST point before next character, so we can increment
  39      it while memory is read (wins on pipelined cpus).  */
  40   ++destlen;
  41   dest -= 2;
  42
  43   if (n >= 4)
  44     {
  45       size_t n4 = n >> 2;
  46       do
  47         {
  48           if (__glibc_unlikely (destlen-- == 0))
  49             __chk_fail ();
  50           c = *src++;
  51           *++dest = c;
  52           if (c == L'\0')
  53             return s;
  54           if (__glibc_unlikely (destlen-- == 0))
  55             __chk_fail ();
  56           c = *src++;
  57           *++dest = c;
  58           if (c == L'\0')
  59             return s;
  60           if (__glibc_unlikely (destlen-- == 0))
  61             __chk_fail ();
  62           c = *src++;
  63           *++dest = c;
  64           if (c == L'\0')
  65             return s;
  66           if (__glibc_unlikely (destlen-- == 0))
  67             __chk_fail ();
  68           c = *src++;
  69           *++dest = c;
  70           if (c == L'\0')
  71             return s;
  72         } while (--n4 > 0);
  73       n &= 3;
  74     }
  75
  76   while (n > 0)
  77     {
  78       if (__glibc_unlikely (destlen-- == 0))
  79         __chk_fail ();
  80       c = *src++;
  81       *++dest = c;
  82       if (c == L'\0')
  83         return s;
  84       n--;
  85     }
  86
  87   if (c != L'\0')
  88     {
  89       if (__glibc_unlikely (destlen-- == 0))
  90         __chk_fail ();
  91       *++dest = L'\0';
  92     }
  93
  94   return s;
  95 }