wcsmbs/wcsncat.c

   1 /* Copyright (C) 1995, 1996, 1997 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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <wchar.h>
  21
  22
  23 /* Append no more than N wide-character of SRC onto DEST.  */
  24 wchar_t *
  25 wcsncat (dest, src, n)
  26      wchar_t *dest;
  27      const wchar_t *src;
  28      size_t n;
  29 {
  30   wchar_t c;
  31   wchar_t * const s = dest;
  32
  33   /* Find the end of DEST.  */
  34   do
  35     c = *dest++;
  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   dest -= 2;
  41
  42   if (n >= 4)
  43     {
  44       size_t n4 = n >> 2;
  45       do
  46         {
  47           c = *src++;
  48           *++dest = c;
  49           if (c == L'\0')
  50             return s;
  51           c = *src++;
  52           *++dest = c;
  53           if (c == L'\0')
  54             return s;
  55           c = *src++;
  56           *++dest = c;
  57           if (c == L'\0')
  58             return s;
  59           c = *src++;
  60           *++dest = c;
  61           if (c == L'\0')
  62             return s;
  63         } while (--n4 > 0);
  64       n &= 3;
  65     }
  66
  67   while (n > 0)
  68     {
  69       c = *src++;
  70       *++dest = c;
  71       if (c == L'\0')
  72         return s;
  73       n--;
  74     }
  75
  76   if (c != L'\0')
  77     *++dest = L'\0';
  78
  79   return s;
  80 }