Subversion Repositories svnkaklik

<?php

/*

Programming info

All functions output a small array, which we'll call $return for now.

$return[0] is the data expected of the function

$return[1] is the offset over the whole bencoded data of the next

          piece of data.

numberdecode returns [0] as the integer read, and [1]-1 points to the

symbol that was interprented as the end of the interger (either "e" or

":").

numberdecode is used for integer decodes both for i11e and 11:hello there

so it is tolerant of the ending symbol.

decodelist returns $return[0] as an integer indexed array like you would use in C

for all the entries. $return[1]-1 is the "e" that ends the list, so [1] is the next

useful byte.

decodeDict returns $return[0] as an array of text-indexed entries. For example,

$return[0]["announce"] = "http://www.whatever.com:6969/announce";

$return[1]-1 again points to the "e" that ends the dictionary.

decodeEntry returns [0] as an integer in the case $offset points to

i12345e or a string if $offset points to 11:hello there style strings.

It also calls decodeDict or decodeList if it encounters a d or an l.

Known bugs:

- The program doesn't pay attention to the string it's working on.

 A zero-sized or truncated data block will cause string offset errors

 before they get rejected by the decoder. This is worked around by

 suppressing errors.

*/

// Protect our namespace using a class

class BDecode

{

    function numberdecode($wholefile, $start)

    {

        $ret[0] = 0;

        $offset = $start;

        // Funky handling of negative numbers and zero

        $negative = false;

        if ($wholefile[$offset] == '-')

        {

             $negative = true;

             $offset++;

        }

        if ($wholefile[$offset] == '0')

        {

            $offset++;

            if ($negative)

            {

                return array(false);

            }

            if ($wholefile[$offset] == ':' || $wholefile[$offset] == 'e')

            {

                $offset++;

                $ret[0] = 0;

                $ret[1] = $offset;

                return $ret;

            }

            return array(false);

        }

        while (true)

        {

            if ($wholefile[$offset] >= '0' && $wholefile[$offset] <= '9')

            {

                $ret[0] *= 10;

            //Added 2005.02.21 - VisiGod

            //Changing the type of variable from integer to double to prevent a numeric overflow

                settype($ret[0],"double");

            //Added 2005.02.21 - VisiGod

                $ret[0] += ord($wholefile[$offset]) - ord("0");

                $offset++;

            }

            // Tolerate : or e because this is a multiuse function

            else if ($wholefile[$offset] == 'e' || $wholefile[$offset] == ':')

            {

                $ret[1] = $offset+1;

                if ($negative)

                {

                    if ($ret[0] == 0)

                    {

                        return array(false);

                    }

                    $ret[0] = - $ret[0];

                }

                return $ret;

            }

            else

            {

                return array(false);

            }

        }

        return array(false);

    }

    function decodeEntry($wholefile, $offset=0)

    {

        if ($wholefile[$offset] == 'd')

        {

            return $this->decodeDict($wholefile, $offset);

        }

        if ($wholefile[$offset] == 'l')

        {

            return $this->decodelist($wholefile, $offset);

        }

        if ($wholefile[$offset] == "i")

        {

            $offset++;

            return $this->numberdecode($wholefile, $offset);

        }

        // String value: decode number, then grab substring

        $info = $this->numberdecode($wholefile, $offset);

        if ($info[0] === false)

        {

            return array(false);

        }

        $ret[0] = substr($wholefile, $info[1], $info[0]);

        $ret[1] = $info[1]+strlen($ret[0]);

        return $ret;

    }

    function decodeList($wholefile, $start)

    {

        $offset = $start+1;

        $i = 0;

        if ($wholefile[$start] != 'l')

        {

            return array(false);

        }

        $ret = array();

        while (true)

        {

            if ($wholefile[$offset] == 'e')

            {

                break;

            }

            $value = $this->decodeEntry($wholefile, $offset);

            if ($value[0] === false)

            {

                return array(false);

            }

            $ret[$i] = $value[0];

            $offset = $value[1];

            $i ++;

        }

        // The empy list is an empty array. Seems fine.

        $final[0] = $ret;

        $final[1] = $offset+1;

        return $final;

    }

// Tries to construct an array

    function decodeDict($wholefile, $start=0)

    {

        $offset = $start;

        if ($wholefile[$offset] == 'l')

        {

            return $this->decodeList($wholefile, $start);

        }

        if ($wholefile[$offset] != 'd')

        {

            return false;

        }

        $ret = array();

        $offset++;

        while (true)

        {

            if ($wholefile[$offset] == 'e')

            {

                $offset++;

                break;

            }

            $left = $this->decodeEntry($wholefile, $offset);

            if (!$left[0])

            {

                return false;

            }

            $offset = $left[1];

            if ($wholefile[$offset] == 'd')

            {

                // Recurse

                $value = $this->decodedict($wholefile, $offset);

                if (!$value[0])

                {

                    return false;

                }

                $ret[addslashes($left[0])] = $value[0];

                $offset= $value[1];

                continue;

            }

            else if ($wholefile[$offset] == 'l')

            {

                $value = $this->decodeList($wholefile, $offset);

                if (!$value[0] && is_bool($value[0]))

                {

                    return false;

                }

                $ret[addslashes($left[0])] = $value[0];

                $offset = $value[1];

            }

            else

            {

                $value = $this->decodeEntry($wholefile, $offset);

                if ($value[0] === false)

                {

                    return false;

                }

                $ret[addslashes($left[0])] = $value[0];

                $offset = $value[1];

            }

        }

        if (empty($ret))

        {

            $final[0] = true;

        }

        else

        {

            $final[0] = $ret;

        }

        $final[1] = $offset;

        return $final;

    }

} // End of class declaration.

// Use this function. eg:  BDecode("d8:announce44:http://www. ... e");

function BDecode($wholefile)

{

    $decoder = new BDecode;

    $return = $decoder->decodeEntry($wholefile);

    return $return[0];

}

?>