wcstomb.c

ReactOS是一些高手根据Windows XP的内核编写出的类XP。内核实现机理和API函数调用几乎相同。甚至可以兼容XP的程序。喜欢研究系统内核的人可以看一看。

/* Copyright (C) 1991, 1992, 1995, 1996, 1997 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <precomp.h>
#include <wchar.h>

#ifndef EILSEQ
#define EILSEQ EINVAL
#endif

static const wchar_t encoding_mask[] =
{
  (wchar_t)~0x7ff, (wchar_t)~0xffff, (wchar_t)~0x1fffff, (wchar_t)~0x3ffffff
};

static const unsigned char encoding_byte[] =
{
  0xc0, 0xe0, 0xf0, 0xf8, 0xfc
};

/* The state is for this UTF8 encoding not used.  */
//static mbstate_t internal;


//extern mbstate_t __no_r_state;  /* Defined in mbtowc.c.  */

size_t
__wcrtomb (char *s, wchar_t wc);

/*
 * Convert WCHAR into its multibyte character representation,
 * putting this in S and returning its length.
 *
 * Attention: this function should NEVER be intentionally used.
 * The interface is completely stupid.  The state is shared between
 * all conversion functions.  You should use instead the restartable
 * version `wcrtomb'.
 *
 * @implemented
 */
int
wctomb (char *s, wchar_t wchar)
{
  /* If S is NULL the function has to return null or not null
     depending on the encoding having a state depending encoding or
     not.  This is nonsense because any multibyte encoding has a
     state.  The ISO C amendment 1 corrects this while introducing the
     restartable functions.  We simply say here all encodings have a
     state.  */
  if (s == NULL)
    return 1;

  return __wcrtomb (s, wchar);
}


size_t
__wcrtomb (char *s, wchar_t wc)
{
  char fake[1];
  size_t written = 0;



  if (s == NULL)
    {
      s = fake;
      wc = L'\0';
    }

  if (wc < 0x80)
    {
      /* It's a one byte sequence.  */
      if (s != NULL)
        *s = (char) wc;
      return 1;
    }

  for (written = 2; written < 6; ++written)
    if ((wc & encoding_mask[written - 2]) == 0)
      break;

  if (s != NULL)
    {
      size_t cnt = written;
      s[0] = encoding_byte[cnt - 2];

      --cnt;
      do
        {
          s[cnt] = 0x80 | (wc & 0x3f);
          wc >>= 6;
        }
      while (--cnt > 0);
      s[0] |= wc;
    }

  return written;
}