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itismadness
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<?php
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namespace ApolloRip\BencodeTorrent;
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/**
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* BEncode service that allows us to encode PHP objects into BEncode and decode
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* BEncode into PHP objects for torrents. BEncode supports the following PHP objects:
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* - Associated Array
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* - Lists
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* - Strings
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* - Integers
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* with any other type throwing an exception. A list is defined for our purposes
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* as an array with only numeric keys in perfect order, otherwise we assume it's
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* an associated array and will encode as a dictionary.
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*
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* Additionally, as this is for torrent files, we can make the following assumptions
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* and requirements:
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* 1. Top level data structure must be a dictionary
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* 2. Dictionary must contain an info key
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* If any of these are violated, then we raise an exception for this particular file.
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*
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* @see https://wiki.theory.org/index.php/BitTorrentSpecification
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*
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* For Gazelle, this also acts as a unification of the two original BEncode implementations
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* which were both used in separate areas of the codebase.
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*/
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class BencodeTorrent {
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const FILELIST_DELIM = 0xF7;
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private static $utf8_filelist_delim = null;
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private $data;
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public function __construct() {
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$this->setDelim();
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}
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private function setDelim() {
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if (BencodeTorrent::$utf8_filelist_delim === null) {
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BencodeTorrent::$utf8_filelist_delim = utf8_encode(chr(BencodeTorrent::FILELIST_DELIM));
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}
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}
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/**
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* @param array $data
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* @throws \Exception
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*/
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public function setData($data) {
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$this->data = $data;
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$this->validate();
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}
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/**
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* @param string $data
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* @throws \Exception
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*/
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public function decodeData(string $data) {
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$this->data = $this->decode($data);
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$this->validate();
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}
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/**
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* @param string $path
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* @throws \Exception
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*/
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public function decodeFile(string $path) {
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$this->data = $this->decode(file_get_contents($path, FILE_BINARY));
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$this->validate();
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}
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/**
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* @param string $data
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* @param int $pos
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* @return array|bool|float|string
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*/
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private function decode(string $data, int &$pos = 0) {
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if ($data[$pos] === 'd') {
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$pos++;
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$return = [];
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while ($data[$pos] !== 'e') {
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$key = $this->decode($data, $pos);
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$value = $this->decode($data, $pos);
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if (empty($key) || empty($value)) {
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break;
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}
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$return[$key] = $value;
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}
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$pos++;
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}
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elseif ($data[$pos] === 'l') {
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$pos++;
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$return = [];
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while ($data[$pos] !== 'e') {
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$value = $this->decode($data, $pos);
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$return[] = $value;
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}
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$pos++;
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}
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elseif ($data[$pos] === 'i') {
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$pos++;
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$digits = strpos($data, 'e', $pos) - $pos;
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$return = (int) substr($data, $pos, $digits);
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$pos += $digits + 1;
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}
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else {
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$digits = strpos($data, ':', $pos) - $pos;
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$len = (int) substr($data, $pos, $digits);
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$pos += ($digits + 1);
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$return = substr($data, $pos, $len);
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$pos += $len;
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}
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return $return;
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}
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public function getData() {
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return $this->data;
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}
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/**
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* @throws \Exception
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*/
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public function validate() {
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if (empty($this->data['info'])) {
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throw new \Exception("Torrent dictionary doesn't have info key");
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}
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}
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/**
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* @throws \RuntimeException
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*/
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private function hasData() {
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if (empty($this->data) || !is_array($this->data)) {
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throw new \RuntimeException('Must decode proper bencode string first');
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}
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}
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/**
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* @return string
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*/
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public function getEncode() {
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$this->hasData();
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return $this->encodeVal($this->data);
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}
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/**
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* @param $data
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* @return string
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*/
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private function encodeVal($data) {
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if (is_array($data)) {
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$return = '';
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$check = -1;
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$list = true;
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foreach ($data as $key => $value) {
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if ($key !== ++$check) {
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$list = false;
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break;
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}
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}
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if ($list) {
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$return .= 'l';
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foreach ($data as $value) {
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$return .= $this->encodeVal($value);
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}
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}
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else {
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$return .= 'd';
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foreach ($data as $key => $value) {
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$return .= $this->encodeVal(strval($key));
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$return .= $this->encodeVal($value);
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}
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}
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$return .= 'e';
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}
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elseif (is_integer($data)) {
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$return = 'i'.$data.'e';
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}
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else {
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$return = strlen($data) . ':' . $data;
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}
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return $return;
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}
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/**
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* Utility function to clean out keys in the data and info dictionaries that we don't need in our torrent file
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* when we go to store it in the DB or serve it up to the user (with the expectation that we'll be calling at
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* least setAnnounceUrl(...) when a user asks for a valid torrent file).
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*
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* @return bool flag to indicate if we altered the info dictionary
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*/
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public function clean() {
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$this->cleanDataDictionary();
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return $this->cleanInfoDictionary();
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}
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/**
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* Clean out keys within the data dictionary that are not strictly necessary or will be overwritten dynamically
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* on any downloaded torrent (like announce or comment), so that we store the smallest encoded string within the
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* database and cuts down on potential waste.
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*/
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public function cleanDataDictionary() {
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$allowed_keys = array('encoding', 'info');
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foreach ($this->data['info'] as $key => $value) {
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if (!in_array($key, $allowed_keys)) {
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unset($this->data['info'][$key]);
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}
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}
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}
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/**
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* Cleans out keys within the info dictionary (and would affect the info hash).
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* @return bool
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*/
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public function cleanInfoDictionary() {
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$cleaned = false;
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$allowed_keys = array('files', 'name', 'piece length', 'pieces', 'private', 'length', 'name.utf8', 'name.utf-8',
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'md5sum', 'sha1', 'source', 'file-duration', 'file-media');
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foreach ($this->data['info'] as $key => $value) {
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if (!in_array($key, $allowed_keys)) {
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unset($this->data['info'][$key]);
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$cleaned = true;
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}
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}
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return $cleaned;
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}
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/**
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* Returns a bool on whether the private flag set to 1 within the info dictionary.
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*
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* @return bool
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*/
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public function isPrivate() {
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$this->hasData();
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return isset($this->data['info']['private']) && $this->data['info']['private'] === 1;
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}
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/**
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* Sets the private flag (if not already set) in the info dictionary. Setting this to 1 makes it so a client
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* will only publish its presence in the swarm via the tracker in the announce URL, else it'll be discoverable
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* via other means such as PEX peer exchange or dht, which is a negative for security and privacy of a private
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* swarm. Returns a bool on whether or not the flag was changed so that an appropriate screen can be shown to the
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* user.
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*
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* @return bool
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*/
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public function makePrivate() {
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$this->hasData();
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if ($this->isPrivate()) {
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return false;
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}
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$this->data['info']['private'] = 1;
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ksort($this->data['info']);
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return true;
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}
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/**
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* Set the source flag in the info dictionary equal to $source. This can be used to ensure a unique info hash
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* across sites so long as all sites use the source flag. This isn't an 'official' flag (no accepted BEP on it),
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* but it has become the defacto standard with more clients supporting it natively. Returns a boolean on whether
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* or not the source was changed so that an appropriate screen can be shown to the user.
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*
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* @param $source
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*
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* @return bool true if the source was set/changed, false if no change
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*/
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public function setSource($source) {
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$this->hasData();
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if (isset($this->data['info']['source']) && $this->data['info']['source'] === $source) {
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return false;
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}
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$this->data['info']['source'] = $source;
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ksort($this->data['info']);
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return true;
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}
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public function setAnnounceUrl($announce_url) {
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$this->hasData();
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$this->data['announce'] = $announce_url;
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ksort($this->data);
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}
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public function setComment($comment) {
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$this->hasData();
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$this->data['comment'] = $comment;
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ksort($this->data);
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}
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/**
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* Get a sha1 encoding of the BEncoded info dictionary
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* @return string
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*/
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public function getInfoHash() {
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$this->hasData();
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return sha1($this->encodeVal($this->data['info']));
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}
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/**
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* @return string
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*/
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public function getName() {
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if (isset($this->data['info']['name.utf-8'])) {
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return $this->data['info']['name.utf-8'];
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}
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return $this->data['info']['name'];
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}
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public function getSize() {
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$cur_size = 0;
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if (!isset($this->data['info']['files'])) {
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$cur_size = $this->data['info']['length'];
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}
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else {
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foreach ($this->data['info']['files'] as $file) {
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$cur_size += $file['length'];
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}
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}
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return $cur_size;
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}
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public function getFileList() {
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$files = [];
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if (!isset($this->data['info']['files'])) {
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// Single-file torrent
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$name = (isset($this->data['info']['name.utf-8']) ? $this->data['info']['name.utf-8'] : $this->data['info']['name']);
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$size = $this->data['info']['length'];
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$files[] = array('name' => $name, 'size' => $size);
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}
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else {
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$path_key = isset($this->data['info']['files'][0]['path.utf-8']) ? 'path.utf-8' : 'path';
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foreach ($this->data['info']['files'] as $file) {
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$tmp_path = array();
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foreach ($file[$path_key] as $sub_path) {
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$tmp_path[] = $sub_path;
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}
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$files[] = array('name' => implode('/', $tmp_path), 'size' => $file['length']);
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}
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uasort($files, function($a, $b) {
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return strnatcasecmp($a['name'], $b['name']);
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});
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}
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return $files;
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}
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public function getGazelleFileList() {
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$files = [];
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foreach ($this->getFileList() as $file) {
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$name = $file['name'];
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$size = $file['length'];
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$name = BencodeTorrent::makeUTF8(strtr($name, "\n\r\t", ' '));
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$ext_pos = strrpos($name, '.');
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// Should not be $ExtPos !== false. Extensionless files that start with a . should not get extensions
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$ext = ($ext_pos ? trim(substr($name, $ext_pos + 1)) : '');
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$files[] = sprintf("%s s%ds %s %s", ".$ext", $size, $name, BencodeTorrent::$utf8_filelist_delim);
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}
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return $files;
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}
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private static function makeUTF8($Str) {
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if ($Str != '') {
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if (BencodeTorrent::isUTF8($Str)) {
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$Encoding = 'UTF-8';
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}
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if (empty($Encoding)) {
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$Encoding = mb_detect_encoding($Str, 'UTF-8, ISO-8859-1');
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}
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if (empty($Encoding)) {
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$Encoding = 'ISO-8859-1';
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}
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if ($Encoding == 'UTF-8') {
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return $Str;
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}
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else {
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return @mb_convert_encoding($Str, 'UTF-8', $Encoding);
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}
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}
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}
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private static function isUTF8($Str) {
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return preg_match('%^(?:
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[\x09\x0A\x0D\x20-\x7E] // ASCII
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| [\xC2-\xDF][\x80-\xBF] // non-overlong 2-byte
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| \xE0[\xA0-\xBF][\x80-\xBF] // excluding overlongs
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| [\xE1-\xEC\xEE\xEF][\x80-\xBF]{2} // straight 3-byte
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| \xED[\x80-\x9F][\x80-\xBF] // excluding surrogates
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| \xF0[\x90-\xBF][\x80-\xBF]{2} // planes 1-3
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| [\xF1-\xF3][\x80-\xBF]{3} // planes 4-15
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| \xF4[\x80-\x8F][\x80-\xBF]{2} // plane 16
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)*$%xs', $Str
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);
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}
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}
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