/* Look at first character in UTF-8 string, returning an error code.

   Copyright (C) 1999-2002, 2006-2007, 2009-2018 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 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 "unistr.h"

int

u8_mbtoucr (ucs4_t *puc, const uint8_t *s, size_t n)

{

  uint8_t c = *s;

  if (c < 0x80)

    {

      *puc = c;

      return 1;

    }

  else if (c >= 0xc2)

    {

      if (c < 0xe0)

        {

          if (n >= 2)

            {

              if ((s[1] ^ 0x80) < 0x40)

                {

                  *puc = ((unsigned int) (c & 0x1f) << 6)

                         | (unsigned int) (s[1] ^ 0x80);

                  return 2;

                }

              /* invalid multibyte character */

            }

          else

            {

              /* incomplete multibyte character */

              *puc = 0xfffd;

              return -2;

            }

        }

      else if (c < 0xf0)

        {

          if (n >= 2)

            {

              if ((s[1] ^ 0x80) < 0x40

                  && (c >= 0xe1 || s[1] >= 0xa0)

                  && (c != 0xed || s[1] < 0xa0))

                {

                  if (n >= 3)

                    {

                      if ((s[2] ^ 0x80) < 0x40)

                        {

                          *puc = ((unsigned int) (c & 0x0f) << 12)

                                 | ((unsigned int) (s[1] ^ 0x80) << 6)

                                 | (unsigned int) (s[2] ^ 0x80);

                          return 3;

                        }

                      /* invalid multibyte character */

                    }

                  else

                    {

                      /* incomplete multibyte character */

                      *puc = 0xfffd;

                      return -2;

                    }

                }

              /* invalid multibyte character */

            }

          else

            {

              /* incomplete multibyte character */

              *puc = 0xfffd;

              return -2;

            }

        }

      else if (c < 0xf8)

        {

          if (n >= 2)

            {

              if ((s[1] ^ 0x80) < 0x40

                  && (c >= 0xf1 || s[1] >= 0x90)

                  && (c < 0xf4 || (c == 0xf4 && s[1] < 0x90)))

                {

                  if (n >= 3)

                    {

                      if ((s[2] ^ 0x80) < 0x40)

                        {

                          if (n >= 4)

                            {

                              if ((s[3] ^ 0x80) < 0x40)

                                {

                                  *puc = ((unsigned int) (c & 0x07) << 18)

                                         | ((unsigned int) (s[1] ^ 0x80) << 12)

                                         | ((unsigned int) (s[2] ^ 0x80) << 6)

                                         | (unsigned int) (s[3] ^ 0x80);

                                  return 4;

                                }

                              /* invalid multibyte character */

                            }

                          else

                            {

                              /* incomplete multibyte character */

                              *puc = 0xfffd;

                              return -2;

                            }

                        }

                      /* invalid multibyte character */

                    }

                  else

                    {

                      /* incomplete multibyte character */

                      *puc = 0xfffd;

                      return -2;

                    }

                }

              /* invalid multibyte character */

            }

          else

            {

              /* incomplete multibyte character */

              *puc = 0xfffd;

              return -2;

            }

        }

    }

  /* invalid multibyte character */

  *puc = 0xfffd;

  return -1;

}