Bencode
This is a library used for encoding and decoding bencoded streams. Bencoding
is primarily found in the makeup of .torrent files., (*1)
Bencoding Basics
Pronounced bee-encoding, this encoding focuses on binary encoding with four
basic element data structures., (*2)
IntegerByteListDictionary
The last two elements (List, Dictionary) are just collections of the
first two elements., (*3)
Integer
The Integer element is a positive or negative integer that is always
prefixed with an i, and suffixed with an e., (*4)
i45e
i-1e
Usage
<?php
use Bencode\Integer;
$int = new Integer(45);
echo $int->encode(); // i45e
$int->decode(i-445e);
echo $int->write(); // -445
Byte
Bytes are encoded with their size (in bytes), a : and then the sequence
of bytes., (*5)
5:hello
6:123456
Note that the second example will encode the character codes and not the
binary value of the integers., (*6)
Usage
<?php
use Bencode\Byte;
$byte = new Byte('hello');
echo $byte->encode(); // 5:hello
$byte->decode('5:world');
echo $byte->write(); // world
List
A List is just that, a list of Byte and Integer elements. It has a siilar
encoding as the Integer. The List is prefixed with l and suffixed with
e. Within are encoded Bytes and integers., (*7)
li45e5:hello5:worldi-45e
Usage
The class is named BList because List is a reserved keyword in PHP., (*8)
<?php
use Bencode\Collection\BList
$list = new BList([45, 'hello', 'world', -45]);
echo $list->encode(); // li45e5:hello5:worldi-45e
$list->decode('li34e4:davee');
print_r($list->write()); // [34, 'dave']
Dictionary
Dictionaries are key-value lists. The first element in the list is the key, and
the second is the value. The Dictionary is prefixed with a d and suffixed with
an e., (*9)
d3:key5:valuee
You can also use elements as values in the list., (*10)
d3:keyli3ei5eee
d3:keyd3:key5:valueee
Usage
<?php
use Bencode\Collection\Dictionary;
$dictionary = new Dictionary(['key' => 'value']);
echo $dictionary->encode(); // d3:key5:valuee
$dictionary->decode('d3:new6:valuese');
print_r($dictionary->write()); // ['new' => 'values']
Dictionaries are what your .torrent files are encoded with. You can easily
build objects to manipulate data of a torrent file., (*11)
<?php
use Bencode\Collection\Dictionary;
$dictionary = new Dictionary();
$torrent = file_get_contents('example.torrent');
$ditionary->decode($torrent);
$buffer = $dictionary->write();
echo $buffer['comment'];
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