btrfs-sync-backend/Src/Asio.hpp

#pragma once

#include <boost/asio.hpp>
#include <boost/asio/experimental/awaitable_operators.hpp>
#include <boost/algorithm/string/replace.hpp>
#include <functional>
#include <iostream>
#include <boost/stacktrace.hpp>


using namespace boost::asio::experimental::awaitable_operators;


inline std::string tabulate(const std::string& tb) {
    return boost::algorithm::replace_all_copy(tb, "\n", "\n\t");
}

// #ifdef NDEBUG
#define MAKE_ERROR(text)    { std::stringstream error; error << text << std::endl; throw std::runtime_error(error.str()); }
#define MAKE_WARNING(text)  { std::stringstream error; error << text << std::endl; std::cerr << error.str(); }
// #else
// #define MAKE_ERROR(text)    { std::stringstream error; error << boost::stacktrace::stacktrace(); std::string tb = tabulate(error.str()); error.str(""); error << text << "\n\t" << tb << std::endl; throw std::runtime_error(error.str()); }
// #define MAKE_WARNING(text)  { std::stringstream error; error << boost::stacktrace::stacktrace(); std::string tb = tabulate(error.str()); error.str(""); error << text << "\n\t" << tb << std::endl; std::cerr << error.str(); }
// #endif

#define MAKE_INFO(text)     { std::stringstream info; info << text << std::endl; std::cout << info.str(); }

namespace Asio {

namespace asio = boost::asio;
template<typename Result = void, typename Executor = asio::any_io_executor>
using coro = asio::awaitable<Result, Executor>;

/*
    Асинхроный ожидатель завершения использования ресурса
*/
class AsyncUseControl {
public:
    class Lock {
        AsyncUseControl *AUC;

    public:
        Lock(AsyncUseControl *auc)
            : AUC(auc)
        {}

        Lock()
            : AUC(nullptr)
        {}

        ~Lock() {
            if(AUC)
                unlock();
        }

        Lock(const Lock&) = delete;
        Lock(Lock&& obj)
            : AUC(obj.AUC)
        {
            obj.AUC = nullptr;
        }

        Lock& operator=(const Lock&) = delete;
        Lock& operator=(Lock&& obj) {
            if(&obj == this)
                return *this;

            if(AUC)
                unlock();

            AUC = obj.AUC;
            obj.AUC = nullptr;

            return *this;           
        }

        void unlock() {
            assert(AUC);

            if(--AUC->Uses == 0 && AUC->OnNoUse) {
                asio::post(AUC->IOC, std::move(AUC->OnNoUse));
            }

            AUC = nullptr;
        }
    };

private:
    asio::io_context &IOC;
    bool NoUse = false;
    std::move_only_function<void()> OnNoUse;
    std::atomic_int Uses = 0;

public:
    AsyncUseControl(asio::io_context &ioc)
        : IOC(ioc)
    {}

    template<BOOST_ASIO_COMPLETION_TOKEN_FOR(void()) Token = asio::default_completion_token_t<asio::io_context>>
    auto wait(Token&& token = asio::default_completion_token_t<asio::io_context>()) {
        NoUse = true;

        auto initiation = [this](auto&& token) {
            int value;
            do {
                value = Uses.exchange(-1);
            } while(value == -1);

            OnNoUse = std::move(token);

            if(value == 0) {
                asio::post(IOC, std::move(OnNoUse));
            }

            Uses.exchange(value);
        };

        return asio::async_initiate<Token, void()>(initiation, token);
    }

    Lock use() {
        int value;
        do {
            value = Uses.exchange(-1);
        } while(value == -1);

        if(NoUse) {
            Uses.exchange(value);
            throw boost::system::system_error(asio::error::operation_aborted, "OnNoUse");
        }

        Uses.exchange(++value);
        return Lock(this);
    }
};


/*
    Используется, чтобы вместо уничтожения объекта в умной ссылке, вызвать корутину с co_await asyncDestructor()
*/
class IAsyncDestructible : public std::enable_shared_from_this<IAsyncDestructible> {
protected:
    asio::io_context &IOC;
    AsyncUseControl AUC;

    virtual coro<> asyncDestructor() { co_await AUC.wait(); }

public:
    IAsyncDestructible(asio::io_context &ioc)
        : IOC(ioc), AUC(ioc)
    {}

    virtual ~IAsyncDestructible() {}

protected:
    template<typename T, typename = typename std::is_same<IAsyncDestructible, T>>
    static std::shared_ptr<T> CreateShared(asio::io_context &ioc, T *ptr)
    {
        return std::shared_ptr<T>(ptr, [&ioc](T *ptr) {
            boost::asio::co_spawn(ioc,
                [ptr]() mutable -> coro<> {
                    try {
                        co_await dynamic_cast<IAsyncDestructible*>(ptr)->asyncDestructor();
                    } catch(const std::exception& exc) {
                        std::string error = "IAsyncDestructible<";
                        error += typeid(T).name();
                        error += ">:\n";
                        error += tabulate(exc.what());
                        std::cerr << error << std::endl;
                    }

                    try {
                        delete ptr;
                    } catch(const std::exception& exc) {
                        std::string error = "IAsyncDestructible~<";
                        error += typeid(T).name();
                        error += ">:\n";
                        error += tabulate(exc.what());
                        std::cerr << error << std::endl;
                    }
                    
                },
            boost::asio::detached);
        });
    }

    template<typename T, typename = typename std::is_same<IAsyncDestructible, T>>
    static coro<std::shared_ptr<T>> CreateShared(T *ptr)
    {
        co_return std::shared_ptr<T>(ptr, [ioc = asio::get_associated_executor(co_await asio::this_coro::executor)](T *ptr) {
            boost::asio::co_spawn(ioc,
                [ptr]() mutable -> coro<> {
                    try {
                        co_await dynamic_cast<IAsyncDestructible*>(ptr)->asyncDestructor(); 
                    } catch(const std::exception& exc) {
                        std::string error = "IAsyncDestructible<";
                        error += typeid(T).name();
                        error += ">:\n";
                        std::string subError = exc.what();
                        boost::replace_all(subError, "\n", "\n\t");
                        error += subError;
                        std::cerr << error << std::endl;
                    }

                    asio::post(asio::get_associated_executor(co_await asio::this_coro::executor), [ptr](){ delete ptr; });
                },
            boost::asio::detached);
        });
    }
};

}