wcsmbs/wcsncpy.c

   1 /* Copyright (C) 1995, 1996, 1997, 2005 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 /* Copy no more than N wide-characters of SRC to DEST.  */
  24 wchar_t *
  25 __wcsncpy (dest, src, n)
  26      wchar_t *dest;
  27      const wchar_t *src;
  28      size_t n;
  29 {
  30   wint_t c;
  31   wchar_t *const s = dest;
  32
  33   --dest;
  34
  35   if (n >= 4)
  36     {
  37       size_t n4 = n >> 2;
  38
  39       for (;;)
  40         {
  41           c = *src++;
  42           *++dest = c;
  43           if (c == L'\0')
  44             break;
  45           c = *src++;
  46           *++dest = c;
  47           if (c == L'\0')
  48             break;
  49           c = *src++;
  50           *++dest = c;
  51           if (c == L'\0')
  52             break;
  53           c = *src++;
  54           *++dest = c;
  55           if (c == L'\0')
  56             break;
  57           if (--n4 == 0)
  58             goto last_chars;
  59         }
  60       n = n - (dest - s) - 1;
  61       if (n == 0)
  62         return s;
  63       goto zero_fill;
  64     }
  65
  66  last_chars:
  67   n &= 3;
  68   if (n == 0)
  69     return s;
  70
  71   do
  72     {
  73       c = *src++;
  74       *++dest = c;
  75       if (--n == 0)
  76         return s;
  77     }
  78   while (c != L'\0');
  79
  80  zero_fill:
  81   do
  82     *++dest = L'\0';
  83   while (--n > 0);
  84
  85   return s;
  86 }
  87 weak_alias (__wcsncpy, wcsncpy)