File: mbsinit.c

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/* Test for initial conversion state.
   Copyright (C) 2008-2018 Free Software Foundation, Inc.
   Written by Bruno Haible <bruno@clisp.org>, 2008.

   This program is free software: you can redistribute it and/or
   modify it under the terms of either:

     * the GNU Lesser General Public License as published by the Free
       Software Foundation; either version 3 of the License, or (at your
       option) any later version.

   or

     * the GNU General Public License as published by the Free
       Software Foundation; either version 2 of the License, or (at your
       option) any later version.

   or both in parallel, as here.
   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */

#include <config.h>

/* Specification.  */
#include <wchar.h>

#include "verify.h"

#if GNULIB_defined_mbstate_t

/* Platforms that lack mbsinit() also lack mbrlen(), mbrtowc(), mbsrtowcs()
   and wcrtomb(), wcsrtombs().
   We assume that
     - sizeof (mbstate_t) >= 4,
     - only stateless encodings are supported (such as UTF-8 and EUC-JP, but
       not ISO-2022 variants),
     - for each encoding, the number of bytes for a wide character is <= 4.
       (This maximum is attained for UTF-8, GB18030, EUC-TW.)
   We define the meaning of mbstate_t as follows:
     - In mb -> wc direction, mbstate_t's first byte contains the number of
       buffered bytes (in the range 0..3), followed by up to 3 buffered bytes.
       See mbrtowc.c.
     - In wc -> mb direction, mbstate_t contains no information. In other
       words, it is always in the initial state.  */

verify (sizeof (mbstate_t) >= 4);

int
mbsinit (const mbstate_t *ps)
{
  const char *pstate = (const char *)ps;

  return pstate == NULL || pstate[0] == 0;
}

#else

int
mbsinit (const mbstate_t *ps)
{
# if defined _WIN32 && !defined __CYGWIN__
  /* Native Windows.  */
#  ifdef __MINGW32__
  /* On mingw, 'mbstate_t' is defined as 'int'.  */
  return ps == NULL || *ps == 0;
#  else
  /* MSVC defines 'mbstate_t' as an 8-byte struct; the first 4-bytes matter.  */
  return ps == NULL || *(const unsigned int *)ps == 0;
#  endif
# else
  /* Minix, HP-UX 11.00, Solaris 2.6, Interix, ...  */
  /* Maybe this definition works, maybe not...  */
  return ps == NULL || *(const char *)ps == 0;
# endif
}

#endif