php读取torrent种子文件内容的方法(测试可用)

<?php
/**
 * 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.
 */
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;
  }
}
//使用实例
$s = file_get_contents("test.torrent");
$bc = new xbencoder();
$bc->init();
$bc->decode($s, strlen($s));
var_dump($bc->y);