wcsmbs/wcsncat.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 #ifndef WCSNCAT
  22 # define WCSNCAT wcsncat
  23 #endif
  24
  25 /* Append no more than N wide-character of SRC onto DEST.  */
  26 wchar_t *
  27 WCSNCAT (wchar_t *dest, const wchar_t *src, size_t n)
  28 {
  29   wchar_t c;
  30   wchar_t * const s = dest;
  31
  32   /* Find the end of DEST.  */
  33   do
  34     c = *dest++;
  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   dest -= 2;
  40
  41   if (n >= 4)
  42     {
  43       size_t n4 = n >> 2;
  44       do
  45         {
  46           c = *src++;
  47           *++dest = c;
  48           if (c == L'\0')
  49             return s;
  50           c = *src++;
  51           *++dest = c;
  52           if (c == L'\0')
  53             return s;
  54           c = *src++;
  55           *++dest = c;
  56           if (c == L'\0')
  57             return s;
  58           c = *src++;
  59           *++dest = c;
  60           if (c == L'\0')
  61             return s;
  62         } while (--n4 > 0);
  63       n &= 3;
  64     }
  65
  66   while (n > 0)
  67     {
  68       c = *src++;
  69       *++dest = c;
  70       if (c == L'\0')
  71         return s;
  72       n--;
  73     }
  74
  75   if (c != L'\0')
  76     *++dest = L'\0';
  77
  78   return s;
  79 }