Fossil

    c2 = c;
    c = *++z;
    if( c2>=0x80 ){
      if( ((c2<0xc2) || (c2>=0xf4) || ((c&0xc0)!=0x80)) &&
          (((c2!=0xf4) || (c>=0x90)) && ((c2!=0xc0) || (c!=0x80))) ){
        return LOOK_INVALID; /* Invalid UTF-8 */
      }
      /* the first byte of the sequence is okay
      ** but we need to check the rest
      ** convert next byte to a prefix byte of the next shorter sequence
      ** or a simple space character if the two byte seq was valid
      */
      c = (c2 >= 0xe0) ? (c2<<1)+1 : ' ';
      /* edge case: if three byte sequence started with 0xe0
      ** it becomes 0xc1, which is a too short two byte sequence
      ** so fix it up to be the start of a valid two byte sequence
      */
      if (c == 0xc1) c = 0xc2;
    }
  }
  return (c>=0x80) ? LOOK_INVALID : 0; /* Last byte must be ASCII. */
}


/*