Math or syntax error?

[ShawnD]

I'm trying to write a script which will show the IP of an Emule user based on the user ID entered. The format for the IP decoding is as follows. This is straight from the coders of Emule:

ID = A + B256 + C256² + D*256³

Having the ID you need to extract A, B, C, D using cartesian division of polynoms (int |x| means the non decimal part of x):
D = int |ID / 256³ |
C = int | (ID - D256³⁾ / 256² |
B = int | (ID - D256³ - C256²⁾ / 256 |
A = ID - D256³ - C256² - B256

Now here is my script's main part:

<?php
if (isset($HTTP_POST_VARS['id'])) {
$id = $HTTP_POST_VARS['id'];
$D = $id / (256^3);
$C = ($id - ($D*(256^3))) / (256^2);
$B = ($id - ($D*(256^3)) - ($C*(256^2))) / 256;
$A = ($id - ($D*(256^3)) - ($C*(256^2)) - ($B*256));

echo("The IP is: <br><br>" .$A. "<br>" .$B. "<br>" .$C. "<br>" .$D);
}

?>

Here is what it spits out when I enter the number 1131554628:

The IP is:

4368936.7876448

The first three numbers are 0 because the calculations are using floating point numbers instead of integers. What's driving me crazy is that last number. Remember that it calculates the last number first (the last number is D, the first calculation) and D is not tampered by anything floating point errors. 1131554628 divided by (256³⁾ is not some huge number, it's 67.446 (which would turn into 67 if done properly).

Any help would be very much appreciated.

PS.
Is there any way to force PHP to use integers instead of floating point, or at least force some truncation?

[LordShryku]

Have you tried using bcmath to see if you get closer?
I'm no mathmetician, but just calculating $C gave me 4.80625980584E-06, and I'd expect going father in, it get's uglier...

[drew010]

you can just cast the type.
see this page for examples and explanation

[ShawnD]

Ok I made them all integers, but the problem with the first calculated value (last displayed) still exists.

When I use the value 1131554628 again, here is what I get:

204

4368936

Where does it get 4368936? It's frustrating because it seems so simple but it just doesn't work for some reason. I'm not even sure if that little hat thing (⁾ is acknowledged by PHP. In my calculator, if I leave out the ³ after the 256, the answer for D (last number) is this:
4420135
That's close to the number the script gives:
4368936

My Emule ID is 3791599046, and if worked out with a pencil and paper, the formula really does work. Here is what my script gives:
144

14639378

That last huge number should be 255.

[ShawnD]

Awesome, I got it. Instead of looking for "exponent", I should have been searching for "power". I replaced the hat things with power functions and now the setup works beautifully.

So here's the final working version of the script which can find the IP of any Emule user who repeatedly tries to get a list of your files (probably associated with the RIAA).

<form action="" method="POST">
<table>
<tr>
<td><input type="text" name="id" value="<?php if(isset($HTTP_POST_VARS['id'])) { echo($HTTP_POST_VARS['id']); } ?>">
</td>
<td><input type="submit" name="submit" value="calculate the IP">
</td>
</tr>
</table>
</form>

<?php
if (isset($HTTP_POST_VARS['id'])) {
$id = $HTTP_POST_VARS['id'];
$D = intval( $id / pow(256,3) );
$C = intval( ($id - ($D * pow(256,3))) / pow(256,2) );
$B = intval( ($id - ($D * pow(256,3)) - ($C * pow(256,2))) / 256 );
$A = intval( $id - ($D * pow(256,3)) - ($C * pow(256,2)) - ($B * 256) );

echo("The IP is: <br><br>" .$A. "<br>" .$B. "<br>" .$C. "<br>" .$D);
}

?>

Thanks for all the help guys 🙂