php支持断点续传、分块下载的类

<"\n", "\r\n"))) {
          $is_header_end = 1;
        }
        continue;
      }
      $resp    = fread($fsocket, $speed);
      $read_length = strlen($resp);
      if ($resp === false || $content_length < $total_size + $read_length) {
        fclose($fsocket);
        fclose($file_fp);
        throw new Exception('Socket I/O Error Or File Was Changed');
      }
      $total_size += $read_length;
      fputs($file_fp, $resp);
      // check file end
      if ($content_length == $total_size) {
        break;
      }
      sleep(1);
      // for test
      //break;
    }
    fclose($fsocket);
    fclose($file_fp);
    return true;
 
  }
 
  /**
   * get content length
   *
   * @param $host
   * @param $port
   * @param $url_path
   * @param $headers
   * @param $timeout
   * @return int
   */
  static function get_content_size($host, $port, $url_path, &$headers, $timeout) {
    $request = self::build_header('HEAD', $url_path, $headers);
    $fsocket = @fsockopen($host, $port, $errno, $errstr, $timeout);
    stream_set_blocking($fsocket, TRUE);
    stream_set_timeout($fsocket, $timeout);
    fwrite($fsocket, $request);
    $status = stream_get_meta_data($fsocket);
    $length = 0;
    if ($status['timed_out']) {
      return 0;
    }
    while (!feof($fsocket)) {
      $line = @fgets($fsocket);
      if (in_array($line, array("\n", "\r\n"))) {
        break;
      }
      $line = strtolower($line);
      // get location
      if (substr($line, 0, 9) == 'location:') {
        $location = trim(substr($line, 9));
        $url_info = self::parse_url($location);
        if (!$url_info['host']) {
          return 0;
        }
        fclose($fsocket);
        return self::get_content_size($url_info['host'], $url_info['port'], $url_info['request'], $headers, $timeout);
      }
      // get content length
      if (strpos($line, 'content-length:') !== false) {
        list(, $length) = explode('content-length:', $line);
        $length = (int)trim($length);
      }
    }
    fclose($fsocket);
    return $length;
 
  }
 
  /**
   * build header for socket
   *
   * @param   $action
   * @param   $url_path
   * @param   $headers
   * @param int $range_start
   * @return string
   */
  static function build_header($action, $url_path, &$headers, $range_start = -1) {
    $out = $action . " {$url_path} HTTP/1.0\r\n";
    foreach ($headers as $hkey => $hval) {
      $out .= $hkey . ': ' . $hval . "\r\n";
    }
    if ($range_start > -1) {
      $out .= "Accept-Ranges: bytes\r\n";
      $out .= "Range: bytes={$range_start}-\r\n";
    }
    $out .= "\r\n";
 
    return $out;
  }
}
 
 
#use age
/*
try {
  if (downloader::get('http://dzs.aqtxt.com/files/11/23636/201604230358308081.rar', 'test.rar')) {
    //todo
    echo 'Download Succ';
  }
} catch (Exception $e) {
  echo 'Download Failed';
}
*/
?>