lib/mbsinit.c

   1 /* Test for initial conversion state.
   2    Copyright (C) 2008-2019 Free Software Foundation, Inc.
   3    Written by Bruno Haible <bruno@clisp.org>, 2008.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program 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 General Public License for more details.
  14
  15    You should have received a copy of the GNU 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 #include "verify.h"
  24
  25 #if GNULIB_defined_mbstate_t
  26
  27 /* Platforms that lack mbsinit() also lack mbrlen(), mbrtowc(), mbsrtowcs()
  28    and wcrtomb(), wcsrtombs().
  29    We assume that
  30      - sizeof (mbstate_t) >= 4,
  31      - only stateless encodings are supported (such as UTF-8 and EUC-JP, but
  32        not ISO-2022 variants),
  33      - for each encoding, the number of bytes for a wide character is <= 4.
  34        (This maximum is attained for UTF-8, GB18030, EUC-TW.)
  35    We define the meaning of mbstate_t as follows:
  36      - In mb -> wc direction, mbstate_t's first byte contains the number of
  37        buffered bytes (in the range 0..3), followed by up to 3 buffered bytes.
  38        See mbrtowc.c.
  39      - In wc -> mb direction, mbstate_t contains no information. In other
  40        words, it is always in the initial state.  */
  41
  42 verify (sizeof (mbstate_t) >= 4);
  43
  44 int
  45 mbsinit (const mbstate_t *ps)
  46 {
  47   const char *pstate = (const char *)ps;
  48
  49   return pstate == NULL || pstate[0] == 0;
  50 }
  51
  52 #else
  53
  54 int
  55 mbsinit (const mbstate_t *ps)
  56 {
  57 # if defined _WIN32 && !defined __CYGWIN__
  58   /* Native Windows.  */
  59 #  ifdef __MINGW32__
  60   /* On mingw, 'mbstate_t' is defined as 'int'.  */
  61   return ps == NULL || *ps == 0;
  62 #  else
  63   /* MSVC defines 'mbstate_t' as an 8-byte struct; the first 4-bytes matter.  */
  64   return ps == NULL || *(const unsigned int *)ps == 0;
  65 #  endif
  66 # else
  67   /* Minix, HP-UX 11.00, Solaris 2.6, Interix, ...  */
  68   /* Maybe this definition works, maybe not...  */
  69   return ps == NULL || *(const char *)ps == 0;
  70 # endif
  71 }
  72
  73 #endif