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/***************************************************************************

 *

 * $Id: utf8.c 93 2009-08-24 20:57:31Z Michael.McTernan $

 *

 * UTF8 decode routine.

 * Copyright (C) 2008 Michael C McTernan, Michael.McTernan.2001@cs.bris.ac.uk

 *

 * 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 2

 * 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, write to the Free Software Foundation,

 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA

 **************************************************************************/

/**************************************************************************

 * Includes

 **************************************************************************/

#include "mscgen_utf8.h"


/**************************************************************************

 * Manfest Constants

 **************************************************************************/

/**************************************************************************

 * Macros

 **************************************************************************/

/**************************************************************************

 * Types

 **************************************************************************/

/**************************************************************************

 * Local Variables

 **************************************************************************/

/**************************************************************************

 * Local Functions

 **************************************************************************/

/** Count leading ones from the MSB.

 */
static unsigned int clo(char c)
{
    unsigned int t = 0;

    while((c & (0x80 >> t)) != 0 && t < 8)
    {
        t++;
    }

    return t;
}

/**************************************************************************

 * Global Functions

 **************************************************************************/

Boolean Utf8Decode(const char *s, unsigned int *r, unsigned int *bytes)
{
    if((*s & 0x80) == 0)
    {
        return FALSE;
    }
    else
    {
        unsigned int t;

        /* Set default return values */
        *bytes = clo(*s);
        *r = 0;

        /* Loop through string, checking for null termination */
        for(t = 0; t < *bytes && s[t] != '\0'; t++)
        {
            /* Shift up previous bits */
            *r <<= 6;

            /* Add the required bits */
            if(t == 0)
            {
                *r |= s[t] & (0xff >> (*bytes + 1));
            }
            else
            {
                *r |= s[t] & 0x3f;
            }
        }

        /* Success if no NULL was encountered */
        return t == *bytes;
    }
}

/* END OF FILE */