rf_task.h

#pragma once
 
namespace resumef
{
#ifndef DOXYGEN_SKIP_PROPERTY
 
    struct task_t
    {
        task_t();
        virtual ~task_t();
 
    protected:
        friend scheduler_t;
        counted_ptr<state_base_t> _state;
    };
#endif
 
    //----------------------------------------------------------------------------------------------
 
    template<class _Ty, class = std::void_t<>>
    struct task_impl_t;
 
#ifndef DOXYGEN_SKIP_PROPERTY
    template<class _Ty>
    struct task_impl_t<_Ty, std::void_t<traits::is_future<std::remove_reference_t<_Ty>>>> : public task_t
    {
        using future_type = std::remove_reference_t<_Ty>;
        using value_type = typename future_type::value_type;
        using state_type = state_t<value_type>;
 
        task_impl_t() = default;
        task_impl_t(future_type& f)
        {
            initialize(f);
        }
    protected:
        void initialize(future_type& f)
        {
            _state = f._state.get();
        }
    };
 
    template<class _Ty>
    struct task_impl_t<generator_t<_Ty>> : public task_t
    {
        using value_type = _Ty;
        using future_type = generator_t<value_type>;
        using state_type = state_generator_t;
 
        task_impl_t() = default;
        task_impl_t(future_type& f)
        {
            initialize(f);
        }
    protected:
        void initialize(future_type& f)
        {
            _state = f.detach_state();
        }
    };
 
    //----------------------------------------------------------------------------------------------
 
    //ctx_task_t接受的是一个'函数对象'
    //这个'函数对象'被调用后，返回generator<_Ty>/future_t<_Ty>类型
    //然后'函数对象'作为异步执行的上下文状态保存起来
    template<class _Ctx>
    struct task_ctx_impl_t : public task_impl_t<remove_cvref_t<decltype(std::declval<_Ctx>()())>>
    {
        using context_type = _Ctx;
 
        context_type    _context;
 
        task_ctx_impl_t(context_type ctx)
            : _context(std::move(ctx))
        {
            decltype(auto) f = _context();
            this->initialize(f);
        }
    };
#endif  //DOXYGEN_SKIP_PROPERTY
}