std::ostream &stream() override { return stream_; }
    void map() override {
        std::istreambuf_iterator<char> eos;
        std::istreambuf_iterator<char> it(stream_);
        buf_.insert(buf_.end(), it, eos);
    }
    char *begin() override {
        if(buf_.empty())
            throw std::runtime_error("Buffer is empty: map() not called?");
        return buf_.data();
    }
    char *end() override {
        if(buf_.empty())
            throw std::runtime_error("Buffer is empty: map() not called?");
        return buf_.data() + buf_.size();
    }