1  /* Test for initial conversion state.
       2     Copyright (C) 2008-2023 Free Software Foundation, Inc.
       3     Written by Bruno Haible <bruno@clisp.org>, 2008.
       4  
       5     This file is free software: you can redistribute it and/or modify
       6     it under the terms of the GNU Lesser General Public License as
       7     published by the Free Software Foundation; either version 2.1 of the
       8     License, or (at your option) any later version.
       9  
      10     This file 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
      13     GNU Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser General Public License
      16     along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
      17  
      18  #include <config.h>
      19  
      20  /* Specification.  */
      21  #include <wchar.h>
      22  
      23  
      24  #if GNULIB_defined_mbstate_t
      25  
      26  /* Platforms that lack mbsinit() also lack mbrlen(), mbrtowc(), mbsrtowcs()
      27     and wcrtomb(), wcsrtombs().
      28     We assume that
      29       - sizeof (mbstate_t) >= 4,
      30       - only stateless encodings are supported (such as UTF-8 and EUC-JP, but
      31         not ISO-2022 variants),
      32       - for each encoding, the number of bytes for a wide character is <= 4.
      33         (This maximum is attained for UTF-8, GB18030, EUC-TW.)
      34     We define the meaning of mbstate_t as follows:
      35       - In mb -> wc direction, mbstate_t's first byte contains the number of
      36         buffered bytes (in the range 0..3), followed by up to 3 buffered bytes.
      37         See mbrtowc.c.
      38       - In wc -> mb direction, mbstate_t contains no information. In other
      39         words, it is always in the initial state.  */
      40  
      41  static_assert (sizeof (mbstate_t) >= 4);
      42  
      43  int
      44  mbsinit (const mbstate_t *ps)
      45  {
      46    const char *pstate = (const char *)ps;
      47  
      48    return pstate == NULL || pstate[0] == 0;
      49  }
      50  
      51  #else
      52  
      53  int
      54  mbsinit (const mbstate_t *ps)
      55  {
      56  # if defined _WIN32 && !defined __CYGWIN__
      57    /* Native Windows.  */
      58    /* MSVC defines 'mbstate_t' as an 8-byte struct; the first 4 bytes matter.
      59       On mingw, 'mbstate_t' is sometimes defined as 'int', sometimes defined as
      60       an 8-byte struct, of which the first 4 bytes matter.  */
      61    return ps == NULL || *(const unsigned int *)ps == 0;
      62  # else
      63    /* Minix, HP-UX 11.00, Solaris 2.6, Interix, ...  */
      64    /* Maybe this definition works, maybe not...  */
      65    return ps == NULL || *(const char *)ps == 0;
      66  # endif
      67  }
      68  
      69  #endif