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

   Copyright (C) 1999-2002, 2006-2007, 2009-2024 Free Software Foundation, Inc.

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

   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 "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;

}