EventMultiplexer.h

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/*
 * SNode.C - A Slim Toolkit for Network Communication
 * Copyright (C) Volker Christian <me@vchrist.at>
 *               2020, 2021, 2022, 2023, 2024, 2025
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 * This program is free software: you can redistribute it and/or modify
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 *
 * You should have received a copy of the GNU Lesser General Public License
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 */
 
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 * MIT License
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#ifndef CORE_POLL_EVENTDISPATCHER_H
#define CORE_POLL_EVENTDISPATCHER_H
 
#include "core/EventMultiplexer.h" // IWYU pragma: export
 
namespace core {
    class DescriptorEventReceiver;
}
 
#ifndef DOXYGEN_SHOULD_SKIP_THIS
 
#include "core/system/poll.h" // IWYU pragma: export
 
#include <cstddef>
#include <functional>
#include <limits>
#include <new>
#include <tuple>
#include <unordered_map>
#include <utility>
#include <vector>
 
#endif /* DOXYGEN_SHOULD_SKIP_THIS */
 
namespace core::multiplexer::poll {
 
    class PollFdsManager {
    private:
        template <typename T, typename S>
        class VarSizeTypeAllocator {
        public:
            // Standard allocator typedefs
            using value_type = T;
            using pointer = T*;
            using const_pointer = const T*;
            using void_pointer = void*;
            using const_void_pointer = const void*;
            using size_type = S;
            using difference_type = std::ptrdiff_t;
 
            // Rebind allocator to type U.
            template <typename U>
            struct rebind {
                using other = VarSizeTypeAllocator<U, S>;
            };
 
            // Constructors
            VarSizeTypeAllocator() noexcept {
            }
 
            VarSizeTypeAllocator(const VarSizeTypeAllocator&) noexcept = default;
 
            template <typename U>
            VarSizeTypeAllocator(const VarSizeTypeAllocator<U, S>& /*unused*/) noexcept {
            }
 
            ~VarSizeTypeAllocator() {
            }
 
            // Allocate memory for n objects of type T.
            pointer allocate(size_type n) {
                if (n > max_size()) {
                    throw std::bad_alloc();
                }
                // Allocate using the global operator new.
                return static_cast<pointer>(::operator new(n * sizeof(T)));
            }
 
            // Deallocate memory for n objects of type T.
            void deallocate(pointer p, size_type /*n*/) noexcept {
                ::operator delete(p);
            }
 
            // Returns the maximum number of T objects that can be allocated.
            size_type max_size() const noexcept {
                return std::numeric_limits<size_type>::max() / sizeof(T);
            }
 
            // Construct an object of type U at the given memory location.
            template <typename U, typename... Args>
            void construct(U* p, Args&&... args) {
                ::new (static_cast<void*>(p)) U(std::forward<Args>(args)...);
            }
 
            // Destroy an object of type U.
            template <typename U>
            void destroy(U* p) noexcept {
                p->~U();
            }
 
            // Equality comparisons.
            template <typename U>
            bool operator==(const VarSizeTypeAllocator<U, S>& /*unused*/) const noexcept {
                return true;
            }
 
            template <typename U>
            bool operator!=(const VarSizeTypeAllocator<U, S>& /*unused*/) const noexcept {
                return false;
            }
        };
 
    public:
        using pollfd_vector = std::vector<pollfd, VarSizeTypeAllocator<pollfd, nfds_t>>;
 
        struct PollFdIndex {
            pollfd_vector::size_type index;
            short events;
        };
 
        using pollfdindex_map = std::unordered_map<int,
                                                   PollFdIndex,
                                                   std::hash<int>,
                                                   std::equal_to<>,
                                                   VarSizeTypeAllocator<std::pair<const int, PollFdIndex>, nfds_t>>;
 
        explicit PollFdsManager();
 
        void muxAdd(core::DescriptorEventReceiver* eventReceiver, short event);
        void muxDel(int fd, short event);
        void muxOn(const core::DescriptorEventReceiver* eventReceiver, short event);
        void muxOff(const DescriptorEventReceiver* eventReceiver, short event);
 
        pollfd* getEvents();
 
        const pollfdindex_map& getPollFdIndices() const;
 
        nfds_t getCurrentSize() const;
 
    private:
        nfds_t nextIndex = 0;
        void compress();
 
        pollfd_vector pollfds;
        pollfdindex_map pollFdIndices;
    };
 
    class EventMultiplexer : public core::EventMultiplexer {
    public:
        EventMultiplexer();
        ~EventMultiplexer() override = default;
 
    private:
        int monitorDescriptors(utils::Timeval& tickTimeOut, const sigset_t& sigMask) override;
        void spanActiveEvents(int activeDescriptorCount) override;
 
        PollFdsManager pollFdsManager;
    };
 
} // namespace core::multiplexer::poll
 
#endif // CORE_POLL_EVENTDISPATCHER_H