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glibc  2.9
wcsncpy.c
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00001 /* Copyright (C) 1995, 1996, 1997, 2005 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 /* Copy no more than N wide-characters of SRC to DEST.  */
00024 wchar_t *
00025 __wcsncpy (dest, src, n)
00026      wchar_t *dest;
00027      const wchar_t *src;
00028      size_t n;
00029 {
00030   wint_t c;
00031   wchar_t *const s = dest;
00032 
00033   --dest;
00034 
00035   if (n >= 4)
00036     {
00037       size_t n4 = n >> 2;
00038 
00039       for (;;)
00040        {
00041          c = *src++;
00042          *++dest = c;
00043          if (c == L'\0')
00044            break;
00045          c = *src++;
00046          *++dest = c;
00047          if (c == L'\0')
00048            break;
00049          c = *src++;
00050          *++dest = c;
00051          if (c == L'\0')
00052            break;
00053          c = *src++;
00054          *++dest = c;
00055          if (c == L'\0')
00056            break;
00057          if (--n4 == 0)
00058            goto last_chars;
00059        }
00060       n = n - (dest - s) - 1;
00061       if (n == 0)
00062        return s;
00063       goto zero_fill;
00064     }
00065 
00066  last_chars:
00067   n &= 3;
00068   if (n == 0)
00069     return s;
00070 
00071   do
00072     {
00073       c = *src++;
00074       *++dest = c;
00075       if (--n == 0)
00076        return s;
00077     }
00078   while (c != L'\0');
00079 
00080  zero_fill:
00081   do
00082     *++dest = L'\0';
00083   while (--n > 0);
00084 
00085   return s;
00086 }
00087 weak_alias (__wcsncpy, wcsncpy)