wcsmbs/wcpncpy.c

   1 /* Copyright (C) 1996-2018 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 WCPNCPY
  22 # define __wcpncpy WCPNCPY
  23 #endif
  24
  25 /* Copy no more than N wide-characters of SRC to DEST, returning the
  26    address of the last character written into DEST.  */
  27 wchar_t *
  28 __wcpncpy (wchar_t *dest, const wchar_t *src, size_t n)
  29 {
  30   wint_t c;
  31   wchar_t *const s = dest;
  32
  33   if (n >= 4)
  34     {
  35       size_t n4 = n >> 2;
  36
  37       for (;;)
  38         {
  39           c = *src++;
  40           *dest++ = c;
  41           if (c == L'\0')
  42             break;
  43           c = *src++;
  44           *dest++ = c;
  45           if (c == L'\0')
  46             break;
  47           c = *src++;
  48           *dest++ = c;
  49           if (c == L'\0')
  50             break;
  51           c = *src++;
  52           *dest++ = c;
  53           if (c == L'\0')
  54             break;
  55           if (--n4 == 0)
  56             goto last_chars;
  57         }
  58       n -= dest - s;
  59       goto zero_fill;
  60     }
  61
  62  last_chars:
  63   n &= 3;
  64   if (n == 0)
  65     return dest;
  66
  67   for (;;)
  68     {
  69       c = *src++;
  70       --n;
  71       *dest++ = c;
  72       if (c == L'\0')
  73         break;
  74       if (n == 0)
  75         return dest;
  76     }
  77
  78  zero_fill:
  79   while (n-- > 0)
  80     dest[n] = L'\0';
  81
  82   return dest - 1;
  83 }
  84
  85 #ifndef WCPNCPY
  86 weak_alias (__wcpncpy, wcpncpy)
  87 #endif