dsmithhayes/bencode

A simple bencoding library for PHP.

v0.1.3 2015-10-13 01:26 UTC

Requires (Dev)

• phpunit/phpunit: ^4.7

BSD 3.0

• Dave Smith-Hayes

• bencode
• torrent

README

This is a library used for encoding and decoding bencoded streams. Bencoding is primarily found in the makeup of .torrent files.

Bencoding Basics

Pronounced bee-encoding, this encoding focuses on binary encoding with four basic element data structures.

1. Integer
2. Byte
3. List
4. Dictionary

The last two elements (List, Dictionary) are just collections of the first two elements.

Integer

The Integer element is a positive or negative integer that is always prefixed with an i, and suffixed with an e.

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:hello
6:123456

Note that the second example will encode the character codes and not the binary value of the integers.

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.

li45e5:hello5:worldi-45e

Usage

The class is named BList because List is a reserved keyword in PHP.

<?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.

d3:key5:valuee

You can also use elements as values in the list.

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.

<?php

use Bencode\Collection\Dictionary;

$dictionary = new Dictionary();
$torrent = file_get_contents('example.torrent');

$ditionary->decode($torrent);

$buffer = $dictionary->write();

echo $buffer['comment'];