PHP implementation of bencoding

Copyright 2021 Philippe Paquet

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Description

Bencoding is an encoding algorithm used by the peer-to-peer file sharing system BitTorrent for storing and transmitting loosely structured data. It specify and organize data in a terse format and supports the following types:

• byte strings
• dictionaries
• integers
• lists

Bencoding is part of the BitTorrent specification.

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Usage

Include bencoding.inc.php which specify the bencoding class:

require_once('include/bencoding.inc.php');

Create a bencoding object:

$bencoding = new bencoding();

After creation, the bencoding object offer 3 simple functions:

// Return $string decoded or NULL if there was an error
$value = $bencoding->decode($string);

// Return $value encoded or NULL if there was an error
$string = $bencoding->encode($value);

// Return the last error as a string
$error = $bencoding->error();

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Example

require_once('include/bencoding.inc.php');

$value = array(	'key_1' => 'string',
		'key_2' => 123456,
		'key_3' => array('item_1', 'item_2', 'item_3')
		);

// Create the bencoding object
$bencoding = new bencoding();

// Encode $value
$string = $bencoding->encode($value);
if (NULL === $string) {
	echo $bencoding->error() . PHP_EOL;
} else {
	var_dump($string);
}

echo PHP_EOL;

// Decode $string
$value = $bencoding->decode($string);
if (NULL === $value) {
	echo $bencoding->error() . PHP_EOL;
} else {
	var_dump($value);
}

Will display the following:

string(65) "d5:key_16:string5:key_2i123456e5:key_3l6:item_16:item_26:item_3ee"

array(3) {
  ["key_1"]=>
  string(6) "string"
  ["key_2"]=>
  int(123456)
  ["key_3"]=>
  array(3) {
    [0]=>
    string(6) "item_1"
    [1]=>
    string(6) "item_2"
    [2]=>
    string(6) "item_3"
  }
}

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Contributing

Bug reports and suggestions for improvements are most welcome.

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Contact

If you have any questions, comments or suggestions, do not hesitate to contact me at philippe@paquet.email