1 files changed, 73 insertions, 0 deletions
diff --git a/lib/mbsinit.c b/lib/mbsinit.c
new file mode 100644
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--- /dev/null
+++ b/lib/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 the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   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