var encscans = [0x05,0x10,0x13,0x09,0x32,0x03,0x25,0x11,0x1F,0x17,0x06,
                0x15,0x30,0x19,0x26,0x22,0x0A,0x02,0x2C,0x2F,0x16,0x14,0x07,
                0x18,0x24,0x23,0x31,0x20,0x1E,0x08,0x2D,0x21,0x04,0x0B,0x12,
                0x2E];



function ord(str){
    return str.charCodeAt(0);
}

function StrintToArray(str){
    var arr = [];
    for(var i=0;i<str.length;i++){
        arr[i] = ord(str.charAt(i));
    }
    return arr;
}

function toByte(arr){
    for(var i=0;i<arr.length;i++){
        arr[i] = arr[i] & 0xFF;
    }
    return arr;
}
        

function begin_calc(serial, s_arr){
    var ret_arr = [];
    if(typeof(serial)=="string"){
        serial = StrintToArray(serial);
    }
    
    ret_arr[0] = serial[ s_arr[3] ];
    ret_arr[1] = ( serial[ s_arr[3] ] >> 5) |
                 (( (serial[ s_arr[2] ] >> 5) | (serial[ s_arr[2] ] << 3))
                & 0xF1);
    ret_arr[2] = (serial[ s_arr[2] ] >> 2);
    ret_arr[3] = (serial[ s_arr[2] ] >> 7) | (serial[ s_arr[1] ] << 1);
    ret_arr[4] = (serial[ s_arr[1] ] >> 4) | (serial[ s_arr[0] ] << 4);


    ret_arr[5] = (serial[1] >> 1);
    ret_arr[6] = (serial[1] >> 6) | (serial[0] << 2);
    ret_arr[7] = (serial[0] >> 3);
    

    return toByte(ret_arr);
}

function end_calc(serial, calced_arr, s_arr){
    var r = 0;
    var ret_arr = [];
    for (var i=0;i<8;i++) {
        r = 0xAA;
        (calced_arr[i] & 1) && (r ^= serial[ s_arr[0] ]);
        (calced_arr[i] & 2) && (r ^= serial[ s_arr[1] ]);
        (calced_arr[i] & 4) && ( r ^= serial[ s_arr[2] ]);
        (calced_arr[i] & 8) && (r ^= serial[1]);
        (calced_arr[i] & 16) && (r ^= serial[0]);
        
        ret_arr[i] = encscans[r % encscans.length];
    }
    return ret_arr;
}

function calc_suffix_tag(serial){
    var serial_arr = StrintToArray(serial);
    var ret_arr = begin_calc(serial_arr,[1,2,3,4]);
    return end_calc(serial_arr, ret_arr, [4,3,2]); //8,9.10 For HDD
}

function dell_service_tag(serial){



}