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//

//  bbx_utf8.c

//  babyxrc

//

//  Created by Malcolm McLean on 29/07/2023.

//



#include "bbx_utf8.h"



static const unsigned int offsetsFromUTF8[6] =

{

    0x00000000UL, 0x00003080UL, 0x000E2080UL,

    0x03C82080UL, 0xFA082080UL, 0x82082080UL

};



static const unsigned char trailingBytesForUTF8[256] = {

    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,

    2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, 3,3,3,3,3,3,3,3,4,4,4,4,5,5,5,5

};



int bbx_isutf8z(const char *str)

{

  int len = 0;

  int pos = 0;

  int nb;

  int i;

  int ch;



  while(str[len])

    len++;

  while(pos < len && *str)

  {

    nb = bbx_utf8_skip(str);

    if(nb < 1 || nb > 4)

      return 0;

    if(pos + nb > len)

      return 0;

    for(i=1;i<nb;i++)

      if( (str[i] & 0xC0) != 0x80 )

        return 0;

    ch = bbx_utf8_getch(str);

    if(ch < 0x80)

    {

      if(nb != 1)

        return 0;

    }

    else if(ch < 0x8000)

    {

      if(nb != 2)

        return 0;

    }

    else if(ch < 0x10000)

    {

      if(nb != 3)

        return 0;

    }

    else if(ch < 0x110000)

    {

      if(nb != 4)

        return 0;

    }

    pos += nb;

    str += nb;

  }



  return 1;

}



int bbx_utf8_skip(const char *utf8)

{

  return trailingBytesForUTF8[(unsigned char) *utf8] + 1;

}



int bbx_utf8_getch(const char *utf8)

{

    int ch;

    int nb;



    nb = trailingBytesForUTF8[(unsigned char)*utf8];

    ch = 0;

    switch (nb)

    {

            /* these fall through deliberately */

        case 3: ch += (unsigned char)*utf8++; ch <<= 6;

        case 2: ch += (unsigned char)*utf8++; ch <<= 6;

        case 1: ch += (unsigned char)*utf8++; ch <<= 6;

        case 0: ch += (unsigned char)*utf8++;

    }

    ch -= offsetsFromUTF8[nb];

    

    return ch;

}



int bbx_utf8_putch(char *out, int ch)

{

  char *dest = out;

  if (ch < 0x80)

  {

     *dest++ = (char)ch;

  }

  else if (ch < 0x800)

  {

    *dest++ = (ch>>6) | 0xC0;

    *dest++ = (ch & 0x3F) | 0x80;

  }

  else if (ch < 0x10000)

  {

     *dest++ = (ch>>12) | 0xE0;

     *dest++ = ((ch>>6) & 0x3F) | 0x80;

     *dest++ = (ch & 0x3F) | 0x80;

  }

  else if (ch < 0x110000)

  {

     *dest++ = (ch>>18) | 0xF0;

     *dest++ = ((ch>>12) & 0x3F) | 0x80;

     *dest++ = ((ch>>6) & 0x3F) | 0x80;

     *dest++ = (ch & 0x3F) | 0x80;

  }

  else

    return 0;

  return dest - out;

}



int bbx_utf8_charwidth(int ch)

{

    if (ch < 0x80)

    {

        return 1;

    }

    else if (ch < 0x800)

    {

        return 2;

    }

    else if (ch < 0x10000)

    {

        return 3;

    }

    else if (ch < 0x110000)

    {

        return 4;

    }

    else

        return 0;

}



int bbx_utf8_Nchars(const char *utf8)

{

  int answer = 0;



  while(*utf8)

  {

    utf8 += bbx_utf8_skip(utf8);

    answer++;

  }



  return answer;

}