wcsmbs/wcsncpy.c

   1 /* Copyright (C) 1995-2017 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 #ifdef WCSNCPY
  22 # define __wcsncpy WCSNCPY
  23 #endif
  24
  25 /* Copy no more than N wide-characters of SRC to DEST.  */
  26 wchar_t *
  27 __wcsncpy (wchar_t *dest, const wchar_t *src, size_t n)
  28 {
  29   wint_t c;
  30   wchar_t *const s = dest;
  31
  32   --dest;
  33
  34   if (n >= 4)
  35     {
  36       size_t n4 = n >> 2;
  37
  38       for (;;)
  39         {
  40           c = *src++;
  41           *++dest = c;
  42           if (c == L'\0')
  43             break;
  44           c = *src++;
  45           *++dest = c;
  46           if (c == L'\0')
  47             break;
  48           c = *src++;
  49           *++dest = c;
  50           if (c == L'\0')
  51             break;
  52           c = *src++;
  53           *++dest = c;
  54           if (c == L'\0')
  55             break;
  56           if (--n4 == 0)
  57             goto last_chars;
  58         }
  59       n = n - (dest - s) - 1;
  60       if (n == 0)
  61         return s;
  62       goto zero_fill;
  63     }
  64
  65  last_chars:
  66   n &= 3;
  67   if (n == 0)
  68     return s;
  69
  70   do
  71     {
  72       c = *src++;
  73       *++dest = c;
  74       if (--n == 0)
  75         return s;
  76     }
  77   while (c != L'\0');
  78
  79  zero_fill:
  80   do
  81     *++dest = L'\0';
  82   while (--n > 0);
  83
  84   return s;
  85 }
  86 #ifndef WCSNCPY
  87 weak_alias (__wcsncpy, wcsncpy)
  88 #endif