debug/wcsncat_chk.c

   1 /* Copyright (C) 1995-2023 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    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <wchar.h>
  19
  20
  21 /* Append no more than N wide-character of SRC onto DEST.  */
  22 wchar_t *
  23 __wcsncat_chk (wchar_t *dest, const wchar_t *src, size_t n, size_t destlen)
  24 {
  25   wchar_t c;
  26   wchar_t * const s = dest;
  27
  28   /* Find the end of DEST.  */
  29   do
  30     {
  31       if (__glibc_unlikely (destlen-- == 0))
  32         __chk_fail ();
  33       c = *dest++;
  34     }
  35   while (c != L'\0');
  36
  37   /* Make DEST point before next character, so we can increment
  38      it while memory is read (wins on pipelined cpus).  */
  39   ++destlen;
  40   dest -= 2;
  41
  42   if (n >= 4)
  43     {
  44       size_t n4 = n >> 2;
  45       do
  46         {
  47           if (__glibc_unlikely (destlen-- == 0))
  48             __chk_fail ();
  49           c = *src++;
  50           *++dest = c;
  51           if (c == L'\0')
  52             return s;
  53           if (__glibc_unlikely (destlen-- == 0))
  54             __chk_fail ();
  55           c = *src++;
  56           *++dest = c;
  57           if (c == L'\0')
  58             return s;
  59           if (__glibc_unlikely (destlen-- == 0))
  60             __chk_fail ();
  61           c = *src++;
  62           *++dest = c;
  63           if (c == L'\0')
  64             return s;
  65           if (__glibc_unlikely (destlen-- == 0))
  66             __chk_fail ();
  67           c = *src++;
  68           *++dest = c;
  69           if (c == L'\0')
  70             return s;
  71         } while (--n4 > 0);
  72       n &= 3;
  73     }
  74
  75   while (n > 0)
  76     {
  77       if (__glibc_unlikely (destlen-- == 0))
  78         __chk_fail ();
  79       c = *src++;
  80       *++dest = c;
  81       if (c == L'\0')
  82         return s;
  83       n--;
  84     }
  85
  86   if (c != L'\0')
  87     {
  88       if (__glibc_unlikely (destlen-- == 0))
  89         __chk_fail ();
  90       *++dest = L'\0';
  91     }
  92
  93   return s;
  94 }