Method resize

plugin/handler_socket/libhsclient/string_buffer.hpp:45–51

    begin_offset = end_offset = 0;
  }
  void resize(size_t len) {
    if (size() < len) {
      reserve(len);
      memset(buffer + end_offset, 0, len - size());
    }
    end_offset = begin_offset + len;
  }
  void reserve(size_t len) {
    if (alloc_size >= begin_offset + len) {
      return;