<?

/*
// +--------------------------------------------------------------------------+
// | Project:    NVTracker - NetVision BitTorrent Tracker                     |
// +--------------------------------------------------------------------------+
// | This file is part of NVTracker. NVTracker is based on BTSource,          |
// | originally by RedBeard of TorrentBits, extensively modified by           |
// | Gartenzwerg.                                                             |
// |                                                                          |
// | NVTracker is free software; you can redistribute it and/or modify        |
// | it under the terms of the GNU General Public License as published by     |
// | the Free Software Foundation; either version 2 of the License, or        |
// | (at your option) any later version.                                      |
// |                                                                          |
// | NVTracker is distributed in the hope that it will be useful,             |
// | but WITHOUT ANY WARRANTY; without even the implied warranty of           |
// | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the            |
// | GNU General Public License for more details.                             |
// |                                                                          |
// | You should have received a copy of the GNU General Public License        |
// | along with NVTracker; if not, write to the Free Software Foundation,     |
// | Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA            |
// +--------------------------------------------------------------------------+
// | Obige Zeilen dürfen nicht entfernt werden!    Do not remove above lines! |
// +--------------------------------------------------------------------------+
 */

/*

Basic knowledge of how bencoding works is assumed. Details can be found
at <http://bitconjurer.org/BitTorrent/protocol.html>.



How to use these functions:

An "object" is defined to be an associative array with at least the keys
"type" and "value" present. The "type" key contains a string which is
one of "string", "integer", "list" or "dictionary". The "value" key
contains the appropriate thing, either a string, an integer, a list which
is just a flat array, or a dictionary, which is an associative array. In
the case of "list" and "dictionary", the values of the contained array
are agaib "objects".



Description of the functions:



string benc($obj);

Takes an object as argument and returns the bencoded form of it as string.
Returns the undefined/unset value on failure.

Examples:

benc(array(type => "string", value => "spam"))        returns "4:spam".
benc(array(type => "integer", value => 3))        returns "i3e".
benc(array(type => "list", value => array(
    array(type => "string", value => "spam"),
    array(type => "string", value => "eggs")
)))
                        returns "l4:spam4:eggse"

benc(array(type => "dictionary", value => array(
    cow => array(type => "string", value => "moo"),
    spam => array(type => "string", value => "eggs"),
)))
                    returns "d3:cow3:moo4:spam4:eggse"




object bdec($str);

Returns the object that results from bdecoding the given string. Note
that those aren't real php objects, but merely "objects" as described
above. The returned objects have two additional keys: "string" and
"strlen". They represent the bencoded form of the returned objects, as
it was given in the original bencoded string. Use this to extract
certain portions of a bencoded string without having to re-encode it
(and avoiding possible re-ordering of dictionary keys). $x["strlen"]
is always equivalent to strlen($x["string"]). The "string" attribute
of the top-level returned object will be the same as the original
bencoded string, unless there's trailing garbage at the end of the
string.

This function returns the undefined/unset value on failure.

Example:

bdec("d4:spaml11:spiced pork3:hamee")
    returns this monster:

Array
(
    [type] => dictionary
    [value] => Array
        (
            [spam] => Array
                (
                    [type] => list
                    [value] => Array
                        (
                            [0] => Array
                                (
                                    [type] => string
                                    [value] => spiced pork
                                    [strlen] => 14
                                    [string] => 11:spiced pork
                                )

                            [1] => Array
                                (
                                    [type] => string
                                    [value] => ham
                                    [strlen] => 5
                                    [string] => 3:ham
                                )

                        )

                    [strlen] => 21
                    [string] => l11:spiced pork3:hame
                )

        )

    [strlen] => 29
    [string] => d4:spaml11:spiced pork3:hamee
)





object bdec_file($filename, $maxsize);

Opens the specified file, reads its contents (up to the specified length),
and returns whatever bdec() returns for those contents. This is a simple
convenience function.

*/

function benc($obj) {
    if (!is_array($obj) || !isset($obj["type"]) || !isset($obj["value"]))
        return;
    $c = $obj["value"];
    switch ($obj["type"]) {
        case "string":
            return benc_str($c);
        case "integer":
            return benc_int($c);
        case "list":
            return benc_list($c);
        case "dictionary":
            return benc_dict($c);
        default:
            return;
    }
}

function benc_str($s) {
    return strlen($s) . ":$s";
}

function benc_int($i) {
    return "i" . $i . "e";
}

function benc_list($a) {
    $s = "l";
    foreach ($a as $e) {
        $s .= benc($e);
    }
    $s .= "e";
    return $s;
}

function benc_dict($d) {
    $s = "d";
    $keys = array_keys($d);
    sort($keys);
    foreach ($keys as $k) {
        $v = $d[$k];
        $s .= benc_str($k);
        $s .= benc($v);
    }
    $s .= "e";
    return $s;
}

function bdec_file($f, $ms) {
    $fp = fopen($f, "rb");
    if (!$fp)
        return;
    $e = fread($fp, $ms);
    fclose($fp);
    return bdec($e);
}

function bdec($s) {
    if (preg_match('/^(\d+):/', $s, $m)) {
        $l = $m[1];
        $pl = strlen($l) + 1;
        $v = substr($s, $pl, $l);
        $ss = substr($s, 0, $pl + $l);
        if (strlen($v) != $l)
            return;
        return array(type => "string", value => $v, strlen => strlen($ss), string => $ss);
    }
    if (preg_match('/^i(\d+)e/', $s, $m)) {
        $v = $m[1];
        $ss = "i" . $v . "e";
        if ($v === "-0")
            return;
        if ($v[0] == "0" && strlen($v) != 1)
            return;
        return array(type => "integer", value => $v, strlen => strlen($ss), string => $ss);
    }
    switch ($s[0]) {
        case "l":
            return bdec_list($s);
        case "d":
            return bdec_dict($s);
        default:
            return;
    }
}

function bdec_list($s) {
    if ($s[0] != "l")
        return;
    $sl = strlen($s);
    $i = 1;
    $v = array();
    $ss = "l";
    for (;;) {
        if ($i >= $sl)
            return;
        if ($s[$i] == "e")
            break;
        $ret = bdec(substr($s, $i));
        if (!isset($ret) || !is_array($ret))
            return;
        $v[] = $ret;
        $i += $ret["strlen"];
        $ss .= $ret["string"];
    }
    $ss .= "e";
    return array(type => "list", value => $v, strlen => strlen($ss), string => $ss);
}

function bdec_dict($s) {
    if ($s[0] != "d")
        return;
    $sl = strlen($s);
    $i = 1;
    $v = array();
    $ss = "d";
    for (;;) {
        if ($i >= $sl)
            return;
        if ($s[$i] == "e")
            break;
        $ret = bdec(substr($s, $i));
        if (!isset($ret) || !is_array($ret) || $ret["type"] != "string")
            return;
        $k = $ret["value"];
        $i += $ret["strlen"];
        $ss .= $ret["string"];
        if ($i >= $sl)
            return;
        $ret = bdec(substr($s, $i));
        if (!isset($ret) || !is_array($ret))
            return;
        $v[$k] = $ret;
        $i += $ret["strlen"];
        $ss .= $ret["string"];
    }
    $ss .= "e";
    return array(type => "dictionary", value => $v, strlen => strlen($ss), string => $ss);
}

?>