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+++ b/lib/utf16-ucs4.h
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+/* Conversion UTF-16 to UCS-4.
+   Copyright (C) 2001-2002, 2005-2007 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 2001.
+
+   This program is free software; you can redistribute it and/or modify it
+   under the terms of the GNU Library General Public License as published
+   by the Free Software Foundation; either version 2, 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
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
+   USA.  */
+
+#ifndef _UTF16_UCS4_H
+#define _UTF16_UCS4_H
+
+#include <stddef.h>
+#include "unitypes.h"
+
+extern int u16_mbtouc_aux (ucs4_t *puc, const uint16_t *s, size_t n);
+
+/* Return the length (number of units) of the first character in S, putting
+   its 'ucs4_t' representation in *PUC.
+   The number of available units, N, must be > 0.  */
+static inline int
+u16_mbtouc (ucs4_t *puc, const uint16_t *s, size_t n)
+{
+  uint16_t c = *s;
+
+  if (c < 0xd800 || c >= 0xe000)
+    {
+      *puc = c;
+      return 1;
+    }
+  else
+    return u16_mbtouc_aux (puc, s, n);
+}
+
+#endif /* _UTF16_UCS4_H */