take.hpp

//                  ReactivePlusPlus library
//
//          Copyright Aleksey Loginov 2022 - present.
// Distributed under the Boost Software License, Version 1.0.
//    (See accompanying file LICENSE_1_0.txt or copy at
//          https://www.boost.org/LICENSE_1_0.txt)
//
// Project home: https://github.com/victimsnino/ReactivePlusPlus
//
 
#pragma once
 
#include <rpp/operators/lift.hpp>                          // required due to operator uses lift
#include <rpp/operators/details/subscriber_with_state.hpp> // create_subscriber_with_state
#include <rpp/operators/fwd/take.hpp>
#include <rpp/subscribers/constraints.hpp>
#include <rpp/utils/functors.hpp>
 
IMPLEMENTATION_FILE(take_tag);
 
namespace rpp::details
{
struct take_state
{
    mutable size_t count;
};
 
struct take_on_next
{
    void operator()(auto&& value, const constraint::subscriber auto& subscriber, const take_state& state) const
    {
        if (state.count > 0)
        {
            --state.count;
            subscriber.on_next(std::forward<decltype(value)>(value));
        }
 
        if (state.count == 0)
            subscriber.on_completed();
    }
};
 
template<constraint::decayed_type Type>
struct take_impl
{
    size_t count;
 
    template<constraint::subscriber_of_type<Type> TSub>
    auto operator()(TSub&& subscriber) const
    {
        auto subscription = subscriber.get_subscription();
        // dynamic_state there to make shared_ptr for observer instead of making shared_ptr for state
        return create_subscriber_with_dynamic_state<Type>(std::move(subscription),
                                                          take_on_next{},
                                                          utils::forwarding_on_error{},
                                                          utils::forwarding_on_completed{},
                                                          std::forward<TSub>(subscriber),
                                                          take_state{count});
    }
};
} // namespace rpp::details