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glibc  2.9
wcsncat.c
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00001 /* Copyright (C) 1995, 1996, 1997 Free Software Foundation, Inc.
00002    This file is part of the GNU C Library.
00003    Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu>, 1995.
00004 
00005    The GNU C Library is free software; you can redistribute it and/or
00006    modify it under the terms of the GNU Lesser General Public
00007    License as published by the Free Software Foundation; either
00008    version 2.1 of the License, or (at your option) any later version.
00009 
00010    The GNU C Library is distributed in the hope that it will be useful,
00011    but WITHOUT ANY WARRANTY; without even the implied warranty of
00012    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013    Lesser General Public License for more details.
00014 
00015    You should have received a copy of the GNU Lesser General Public
00016    License along with the GNU C Library; if not, write to the Free
00017    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00018    02111-1307 USA.  */
00019 
00020 #include <wchar.h>
00021 
00022 
00023 /* Append no more than N wide-character of SRC onto DEST.  */
00024 wchar_t *
00025 wcsncat (dest, src, n)
00026      wchar_t *dest;
00027      const wchar_t *src;
00028      size_t n;
00029 {
00030   wchar_t c;
00031   wchar_t * const s = dest;
00032 
00033   /* Find the end of DEST.  */
00034   do
00035     c = *dest++;
00036   while (c != L'\0');
00037 
00038   /* Make DEST point before next character, so we can increment
00039      it while memory is read (wins on pipelined cpus).  */
00040   dest -= 2;
00041 
00042   if (n >= 4)
00043     {
00044       size_t n4 = n >> 2;
00045       do
00046        {
00047          c = *src++;
00048          *++dest = c;
00049          if (c == L'\0')
00050            return s;
00051          c = *src++;
00052          *++dest = c;
00053          if (c == L'\0')
00054            return s;
00055          c = *src++;
00056          *++dest = c;
00057          if (c == L'\0')
00058            return s;
00059          c = *src++;
00060          *++dest = c;
00061          if (c == L'\0')
00062            return s;
00063        } while (--n4 > 0);
00064       n &= 3;
00065     }
00066 
00067   while (n > 0)
00068     {
00069       c = *src++;
00070       *++dest = c;
00071       if (c == L'\0')
00072        return s;
00073       n--;
00074     }
00075 
00076   if (c != L'\0')
00077     *++dest = L'\0';
00078 
00079   return s;
00080 }