wcsmbs/wcsncat.c

   1 /* Copyright (C) 1995-2015 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 (dest, src, n)
  28      wchar_t *dest;
  29      const wchar_t *src;
  30      size_t n;
  31 {
  32   wchar_t c;
  33   wchar_t * const s = dest;
  34
  35   /* Find the end of DEST.  */
  36   do
  37     c = *dest++;
  38   while (c != L'\0');
  39
  40   /* Make DEST point before next character, so we can increment
  41      it while memory is read (wins on pipelined cpus).  */
  42   dest -= 2;
  43
  44   if (n >= 4)
  45     {
  46       size_t n4 = n >> 2;
  47       do
  48         {
  49           c = *src++;
  50           *++dest = c;
  51           if (c == L'\0')
  52             return s;
  53           c = *src++;
  54           *++dest = c;
  55           if (c == L'\0')
  56             return s;
  57           c = *src++;
  58           *++dest = c;
  59           if (c == L'\0')
  60             return s;
  61           c = *src++;
  62           *++dest = c;
  63           if (c == L'\0')
  64             return s;
  65         } while (--n4 > 0);
  66       n &= 3;
  67     }
  68
  69   while (n > 0)
  70     {
  71       c = *src++;
  72       *++dest = c;
  73       if (c == L'\0')
  74         return s;
  75       n--;
  76     }
  77
  78   if (c != L'\0')
  79     *++dest = L'\0';
  80
  81   return s;
  82 }