gl/mbsinit.c

   1 /* Test for initial conversion state.
   2    Copyright (C) 2008, 2009, 2010 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 <http://www.gnu.org/licenses/>.  */
  17
  18 #include <config.h>
  19
  20 /* Specification.  */
  21 #include <wchar.h>
  22
  23 #include "verify.h"
  24
  25 /* Platforms that lack mbsinit() also lack mbrlen(), mbrtowc(), mbsrtowcs()
  26    and wcrtomb(), wcsrtombs().
  27    We assume that
  28      - sizeof (mbstate_t) >= 4,
  29      - only stateless encodings are supported (such as UTF-8 and EUC-JP, but
  30        not ISO-2022 variants),
  31      - for each encoding, the number of bytes for a wide character is <= 4.
  32        (This maximum is attained for UTF-8, GB18030, EUC-TW.)
  33    We define the meaning of mbstate_t as follows:
  34      - In mb -> wc direction, mbstate_t's first byte contains the number of
  35        buffered bytes (in the range 0..3), followed by up to 3 buffered bytes.
  36      - In wc -> mb direction, mbstate_t contains no information. In other
  37        words, it is always in the initial state.  */
  38
  39 verify (sizeof (mbstate_t) >= 4);
  40
  41 int
  42 mbsinit (const mbstate_t *ps)
  43 {
  44   const char *pstate = (const char *)ps;
  45
  46   return pstate[0] == 0;
  47 }