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+/* Test for initial conversion state.
+ Copyright (C) 2008-2022 Free Software Foundation, Inc.
+ Written by Bruno Haible <bruno@clisp.org>, 2008.
+
+ This file is free software: you can redistribute it and/or modify
+ it under the terms of the GNU Lesser General Public License as
+ published by the Free Software Foundation; either version 2.1 of the
+ License, or (at your option) any later version.
+
+ This file 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 Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser 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. */
+ /* MSVC defines 'mbstate_t' as an 8-byte struct; the first 4 bytes matter.
+ On mingw, 'mbstate_t' is sometimes defined as 'int', sometimes defined as
+ an 8-byte struct, of which the first 4 bytes matter. */
+ return ps == NULL || *(const unsigned int *)ps == 0;
+# 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