How to read the contents of BT seed files in php

This article mainly introduces the method of reading the contents of BT seed files in PHP. It can realize the function of reading and displaying the contents of BT seed files. It is simple and practical. Friends in need can refer to it. I hope to be helpful.

The details are as follows:

<?php
/**
 * Class xBEncoder
 * Author: Angus.Fenying
 * Version: 0.1
 *
 *  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] == &#39;d&#39;) {
            $this->y = new xBDict();
            $this->stat = self::READ_DICT;
          } elseif ($s[$i] == &#39;l&#39;) {
            $this->y = array();
            $this->stat = self::READ_LIST;
          }
          break;
        case self::READ_INT:
          if ($s[$i] == &#39;e&#39;) {
            $this->y->val = substr($s, $this->m, $i - $this->m);
            $this->pop();
          }
          break;
        case self::READ_STR:
          if (xBInt::isNum($s[$i]))
            continue;
          if ($s[$i] = &#39;:&#39;) {
            $this->z = substr($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] = &#39;:&#39;) {
            $this->n = substr($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] == &#39;e&#39;) {
            $this->pop();
            break;
          } elseif (!$this->z) {
            $this->m = $i;
            $this->stat = self::READ_KEY;
            break;
          }
        case self::READ_LIST:
          switch ($s[$i]) {
            case &#39;e&#39;:
              $this->pop();
              break;
            case &#39;d&#39;:
              $this->push(new xBDict(), self::READ_DICT);
              break;
            case &#39;i&#39;:
              $this->push(new xBInt(), self::READ_INT);
              $this->m = $i + 1;
              break;
            case &#39;l&#39;:
              $this->push(array(), self::READ_LIST);
              break;
            default:
              if (xBInt::isNum($s[$i])) {
                $this->push(&#39;&#39;, 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) . &#39;:&#39; . $str;
  }
  protected function _encDo($o)
  {
    if (is_string($o))
      return $this->_encStr($o);
    if ($o instanceof xBInt)
      return &#39;i&#39; . $o->val . &#39;e&#39;;
    if ($o instanceof xBDict) {
      $r = &#39;d&#39;;
      foreach ($o as $k => $c)
        $r .= $this->_encStr($k) . $this->_encDo($c);
      return $r . &#39;e&#39;;
    }
    if (is_array($o)) {
      $r = &#39;l&#39;;
      foreach ($o as $c)
        $r .= $this->_encDo($c);
      return $r . &#39;e&#39;;
    }
  }
}
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);

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