gistfile1.txt

    class resource {
        recursive_mutex m_;
        condition_variable cv_;

    public:
        resource() {}
        void with_do(std::function<void()> body)
        {
            m_.lock();
            at_scope_exit u( [&]() { cv_.notify_all(); m_.unlock(); } );
            body();
        }

        void with_when_do(std::function<bool()> cond, std::function<void()> body)
        {
            with_do( [&]() {
                while( !cond() )
                {
                    cv_.wait(m_);
                }
                body(); });
        }

        void await(std::function<bool()> cond)
        {
            while(!cond())
            {
                cv_.wait(m_);
            }
        }

    private:
        resource(const resource&);
        resource& operator=(resource);
    };