help with this code, unpack/pack thing

[Shai-Hulud]

Hi everyone, I'm new here aswell to php

I have this script I'm working on, trying to understand it, it worked out so far until I get to the commands pack, unpack and the part where it is written to disk and then read from disk:

pack part:
$peer_ip = pack("C", $peer_ip[0], $peer_ip[1], $peer_ip[2], $peer_ip[3]);
$peer_port = pack("n", (int)$_GET['port']);

$handle = fopen($info_hash, "rb+");
flock($handle, LOCK_EX);
$peer_num = intval(filesize($info_hash) / 7);
$data = fread($handle, $peer_num 7);
$peer = array();
$updated = false;
for($i=0;$i<$peer_num;$i++)
{
if($peer_ip . $peer_port == substr($data, $i 7 + 1, 6))
{
$updated = true;
if($_GET['event'] == 'stopped')
{
$peer_num--;
}
else
{
$peer[$i] = $time . $peer_ip . $peer_port;
}

    }
    else
    {
            $peer[$i] = substr($data, $i * 7, 7);
    }

}
if($updated == false)
{
$peer[] = $time . $peer_ip . $peer_port;
$peer_num++;
}

rewind($handle);
ftruncate($handle, 0);
fwrite($handle, join('', $peer), $peer_num * 7);
flock($handle, LOCK_UN);
fclose($handle);

unpack part:
$handle = fopen($info_hash, "rb+");
$x = fread($handle, filesize($info_hash));

$ip = unpack("C", substr($x, $j 7 + 1, 4));
$ip = $ip[1] . '.' . $ip[2] . '.' . $ip[3] . '.' . $ip[4];
$port = join('', unpack("n", substr($x, $j 7 + 5, 2)));
$t_peer_seed = join('', unpack("C", substr($x, $j * 7, 1)));

the script I pasted here does not work! I only pasted the parts wich matter in this question!

first I dont understand where they get this numer 7, it pops out all the time

what I would like to ad extra info to the $data array? say I wanted to add uploaded wich ist in bytes so it would be al long string right?

could anyone who is good at php explane exactly what is done at each ommand? this way I can understand the code and I can modify it. (ofcource only if you are in the mood for it, it is a lot of work, thanks 🙂)

thanks in advance for any help on this,

Shai-Hulud

[marky2coats]

What are you trying acheive? This seems extremly complex maybe there is an easier way?

Mark.

[Shai-Hulud]

yes,

I seemed to be a little demanding. after I posted this post I read on an was a little embarresed by the largeness of this question.
I have however studied the code for days and I am beginnign to understand it. this question was simply a product of my impacience.

The only thing thas left actually is how long is the maximum lengh of the read data when you do:

$data = fread($file, "r")

thank,

Shai-Hulud 🙂

[marky2coats]

Well the fread reads in blocks of data. You specify the size of that the data block in the second argument:

fread ( int fp, int length)

$data = fread($file,"r") is in valid as "r" isnt a length. Normaly you would read in blocks of 1024 bytes but it all depends on what your reading. If you want to read the entire contents of a file you can use :

$data = fread($fp,filesize($file));

Also read the manual for any commands you dont understand!

Mark.