/* Look at first character in UTF-8 string.
   Copyright (C) 1999-2000, 2002, 2006-2007 Free Software Foundation, Inc.
   Written by Bruno Haible <bruno@clisp.org>, 2002.

   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.  */

#include <config.h>

/* Specification.  */
#include "unistr.h"

int
u8_strmblen (const uint8_t *s)
{
  /* Keep in sync with unistr.h and utf8-ucs4.c.  */
  uint8_t c = *s;

  if (c < 0x80)
    return (c != 0 ? 1 : 0);
  if (c >= 0xc2)
    {
      if (c < 0xe0)
	{
#if CONFIG_UNICODE_SAFETY
	  if ((s[1] ^ 0x80) < 0x40)
#else
	  if (s[1] != 0)
#endif
	    return 2;
	}
      else if (c < 0xf0)
	{
#if CONFIG_UNICODE_SAFETY
	  if ((s[1] ^ 0x80) < 0x40 && (s[2] ^ 0x80) < 0x40
	      && (c >= 0xe1 || s[1] >= 0xa0)
	      && (c != 0xed || s[1] < 0xa0))
#else
	  if (s[1] != 0 && s[2] != 0)
#endif
	    return 3;
	}
      else if (c < 0xf8)
	{
#if CONFIG_UNICODE_SAFETY
	  if ((s[1] ^ 0x80) < 0x40 && (s[2] ^ 0x80) < 0x40
	      && (s[3] ^ 0x80) < 0x40
	      && (c >= 0xf1 || s[1] >= 0x90)
#if 1
	      && (c < 0xf4 || (c == 0xf4 && s[1] < 0x90))
#endif
	     )
#else
	  if (s[1] != 0 && s[2] != 0 && s[3] != 0)
#endif
	    return 4;
	}
#if 0
      else if (c < 0xfc)
	{
#if CONFIG_UNICODE_SAFETY
	  if ((s[1] ^ 0x80) < 0x40 && (s[2] ^ 0x80) < 0x40
	      && (s[3] ^ 0x80) < 0x40 && (s[4] ^ 0x80) < 0x40
	      && (c >= 0xf9 || s[1] >= 0x88))
#else
	  if (s[1] != 0 && s[2] != 0 && s[3] != 0 && s[4] != 0)
#endif
	    return 5;
	}
      else if (c < 0xfe)
	{
#if CONFIG_UNICODE_SAFETY
	  if ((s[1] ^ 0x80) < 0x40 && (s[2] ^ 0x80) < 0x40
	      && (s[3] ^ 0x80) < 0x40 && (s[4] ^ 0x80) < 0x40
	      && (s[5] ^ 0x80) < 0x40
	      && (c >= 0xfd || s[1] >= 0x84))
#else
	  if (s[1] != 0 && s[2] != 0 && s[3] != 0 && s[4] != 0 && s[5] != 0)
#endif
	    return 6;
	}
#endif
    }
  /* invalid or incomplete multibyte character */
  return -1;
}