LFS Forum - How can I read the Cars-Bytes

I think I found the solution by myself. Trial and error helped me.

This is how I do it (the function argument $cars is equal to the string $tmp from the 1st post):



<?php 
    function decode_cars($cars)
    {
        $binarystring = "";
        // turn the character to an int and this into a binary string
        $tmp = decbin(ord($cars[3])); 
        // add zeros in front of the string until it has 8 digits (because max value of byte is 255, i.e. 11111111)
        while(strlen($tmp) < 8 ) $tmp = "0".$tmp; 
        // the last byte will be the first 8 binary digits
        $binarystring .= $tmp;
        // and so on ...
        $tmp = decbin(ord($cars[2]));
        while(strlen($tmp) < 8 ) $tmp = "0".$tmp;
        $binarystring .= $tmp;
        $tmp = decbin(ord($cars[1]));
        while(strlen($tmp) < 8 ) $tmp = "0".$tmp;
        $binarystring .= $tmp;
        $tmp = decbin(ord($cars[0]));
        while(strlen($tmp) < 8 ) $tmp = "0".$tmp;
        $binarystring .= $tmp;
        
        // just for debugging ...
        // echo "binary string = ".$binarystring."<br>";
        
        $blen = strlen($binarystring); // length of the binary string
        $clen = count($this->carlist); // number of cars in car list
        $count = 0;
        $carnumber = 0;
        $allowedcars = array(); // init the array of allowed cars on the server
        for($i=$blen-1; $i>=0; $i--){ // reverse parsing of the binary string
            if ($binarystring[$i] == "1"){
                $allowedcars[$count] = $this->carlist[$carnumber];
                // just for debugging ...
                // echo "car = ".$this->carlist[$carnumber]."<br>";
                $count++;
            }
            $carnumber++;
        }
        // return the array of allowed cars
        return $allowedcars;
}
?>

The car list is defined by



<?php 
        $this->carlist = array(    "XFG", 
                                "XRG",
                                "XRT",
                                "RB4",
                                "FXO",
                                "LX4",
                                "LX6",
                                "MRT",
                                "UF1",
                                "RAC",
                                "FZ5",
                                "FOX",
                                "XFR",
                                "UFR",
                                "FO8",
                                "FXR",
                                "XRR",
                                "FZR",
                                "BF1"
                               );
?>

Maybe this will help some of you guys, too!

Note that these variables and functions are part of a PHP class, that's why the pointer $this sometimes occur. In a standalone version just remove "$this->".