/* Look at first character in UTF-16 string, returning an error code.

   Copyright (C) 1999-2002, 2006-2007, 2009-2023 Free Software Foundation, Inc.

   Written by Bruno Haible <bruno@clisp.org>, 2001.

   This file is free software.

   It is dual-licensed under "the GNU LGPLv3+ or the GNU GPLv2+".

   You can redistribute it and/or modify it under either

     - the terms of the GNU Lesser General Public License as published

       by the Free Software Foundation, either version 3, or (at your

       option) any later version, or

     - the terms of the GNU General Public License as published by the

       Free Software Foundation; either version 2, or (at your option)

       any later version, or

     - the same dual license "the GNU LGPLv3+ or the GNU GPLv2+".

   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 and the GNU General Public License

   for more details.

   You should have received a copy of the GNU Lesser General Public

   License and of the GNU General Public License along with this

   program.  If not, see <https://www.gnu.org/licenses/>.  */

#include <config.h>

/* Specification.  */

#include "unistr.h"

int

u16_mbtoucr (ucs4_t *puc, const uint16_t *s, size_t n)

{

  uint16_t c = *s;

  if (c < 0xd800 || c >= 0xe000)

    {

      *puc = c;

      return 1;

    }

  if (c < 0xdc00)

    {

      if (n >= 2)

        {

          if (s[1] >= 0xdc00 && s[1] < 0xe000)

            {

              *puc = 0x10000 + ((c - 0xd800) << 10) + (s[1] - 0xdc00);

              return 2;

            }

          /* invalid multibyte character */

        }

      else

        {

          /* incomplete multibyte character */

          *puc = 0xfffd;

          return -2;

        }

    }

  /* invalid multibyte character */

  *puc = 0xfffd;

  return -1;

}