PHP 的 BEncode 操作类（Torrent 文件编码）

首发地址：http://fenying.blog.163.com/blog/static/1020559932014725155573/

原创代码，转载请保留本信息，谢谢阅读。

文/Fenying

　　BT 下载中的种子文件是采用一种叫做 BEncode 的编码表示的，这里给出一种 PHP 解析 BEncode 的方法，可以用来解析和产生 *.torrent 种子文件。

/** * Class xBEncoder * Author:  Angus.Fenying * Version: 0.1 * Date:    2014-06-03 * *   This class helps stringify or parse BENC *   codes. * * All Copyrights 2007 - 2014 Fenying Studio Reserved. * http://fenying.blog.163.com/ */class xBEncoder {const READY = 0;const READ_STR = 1;const READ_DICT = 2;const READ_LIST = 3;const READ_INT = 4;const READ_KEY = 5;public $y;protected $z, $m, $n;protected $stat;protected $stack;/** * This method saves the status of current * encode/decode work. */protected function push($newY, $newStat) {array_push($this->stack, array($this->y, $this->z, $this->m, $this->n, $this->stat));list($this->y, $this->z, $this->m, $this->n, $this->stat) = array($newY, 0, 0, 0, $newStat);}/** * This method restore the saved status of current * encode/decode work. */protected function pop() {$t = array_pop($this->stack);if ($t) {if ($t[4] == self::READ_DICT) {$t[0]->{$t[1]} = $this->y;$t[1] = 0;} elseif ($t[4] == self::READ_LIST)$t[0][] = $this->y;list($this->y, $this->z, $this->m, $this->n, $this->stat) = $t;}}/** * This method initializes the status of work. * YOU SHOULD CALL THIS METHOD BEFORE EVERYTHING. */public function init() {$this->stat = self::READY;$this->stack = array();$this->z = $this->m = $this->n = 0;}/** * This method decode $s($l as length). * You can get $obj->y as the result. */public function decode($s, $l) {$this->y = 0;for ($i = 0; $i < $l; ++$i) {switch ($this->stat) {case self::READY:if ($s[$i] == 'd') {$this->y = new xBDict();$this->stat = self::READ_DICT;} elseif ($s[$i] == 'l') {$this->y = array();$this->stat = self::READ_LIST;}break;case self::READ_INT:if ($s[$i] == 'e') {$this->y->val = substr($s, $this->m, $i - $this->m);$this->pop();}break;case self::READ_STR:if (xBInt::isNum($s[$i])) continue;if ($s[$i] = ':') {$this->z = substr($s, $this->m, $i - $this->m);$this->y = substr($s, $i + 1, $this->z + 0);$i += $this->z;$this->pop();}break;case self::READ_KEY:if (xBInt::isNum($s[$i])) continue;if ($s[$i] = ':') {$this->n = substr($s, $this->m, $i - $this->m);$this->z = substr($s, $i + 1, $this->n + 0);$i += $this->n;$this->stat = self::READ_DICT;}break;case self::READ_DICT:if ($s[$i] == 'e') {$this->pop();break;} elseif (!$this->z) {$this->m = $i;$this->stat = self::READ_KEY;break;}case self::READ_LIST:switch ($s[$i]) {case 'e':$this->pop();break;case 'd':$this->push(new xBDict(), self::READ_DICT);break;case 'i':$this->push(new xBInt(), self::READ_INT);$this->m = $i + 1;break;case 'l':$this->push(array(), self::READ_LIST);break;default:if (xBInt::isNum($s[$i])) {$this->push('', self::READ_STR);$this->m = $i;}}break;}}$rtn = empty($this->stack);$this->init();return $rtn;}/** * This method encode $obj->y into BEncode. */public function encode() {return $this->_encDo($this->y);}protected function _encStr($str) {return strlen($str).':'.$str;}protected function _encDo($o) {if (is_string($o))return $this->_encStr($o);if ($o instanceof xBInt)return 'i'.$o->val.'e';if ($o instanceof xBDict) {$r = 'd';foreach ($o as $k => $c)$r .= $this->_encStr($k).$this->_encDo($c);return $r.'e';}if (is_array($o)) {$r = 'l';foreach ($o as $c)$r .= $this->_encDo($c);return $r.'e';}}}class xBDict {}class xBInt {public $val;public function __construct($val = 0) {$this->val = $val;}public static function isNum($chr) {$chr = ord($chr);if ($chr <= 57 && $chr >= 48)return true;return false;}}

使用范例：

$s = file_get_contents("test.torrent");    $bc = new xBEncoder();    $bc->init();    $bc->decode($s, strlen($s));    var_dump($bc->y);