MSharedMemoryObject.hpp

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// @formatter:off
//
// Balau core C++ library
//
// Copyright (C) 2017 Bora Software (contact@borasoftware.com)
//
// Licensed under the Boost Software License - Version 1.0 - August 17th, 2003.
// See the LICENSE file for the full license text.
//


#ifndef COM_BORA_SOFTWARE__BALAU_INTERPROCESS__MANAGED_SHARED_MEMORY_OBJECT
#define COM_BORA_SOFTWARE__BALAU_INTERPROCESS__MANAGED_SHARED_MEMORY_OBJECT

#include <Balau/Exception/ResourceExceptions.hpp>
#include <Balau/Interprocess/SharedMemoryUtils.hpp>
#include <Balau/Dev/Assert.hpp>
#include <Balau/Type/UUID.hpp>

#include <boost/interprocess/managed_shared_memory.hpp>

namespace Balau::Interprocess {

template <typename T> class MSharedMemoryObject {
    public: template <typename ... P> explicit MSharedMemoryObject(const P & ... params)
        : MSharedMemoryObject(CreateOnly, "SMO_" + UUID().asString(), params ...) {}

    public: template <typename ... P>
    MSharedMemoryObject(CreateOnlySelector, const std::string & name, const P & ... params) {
        const std::string memoryName = name + "_memory";

        boost::interprocess::shared_memory_object::remove(memoryName.c_str());

        segment = boost::interprocess::managed_shared_memory(
            CreateOnly, memoryName.c_str(), metadataOverhead + sizeof(T)
        );

        object = segment.construct<T>((name + "_object").c_str())(params ...);
    }

    public: template <typename ... P>
    MSharedMemoryObject(OpenOrCreateSelector, const std::string & name, const P & ... params) {
        const std::string memoryName = name + "_memory";

        boost::interprocess::shared_memory_object::remove(memoryName.c_str());

        segment = boost::interprocess::managed_shared_memory(
            boost::interprocess::open_or_create, memoryName.c_str(), metadataOverhead + sizeof(T)
        );

        object = segment.construct<T>((name + "_object").c_str())(params ...);
    }

    public: MSharedMemoryObject(OpenOnlySelector, const std::string & name) {
        const std::string memoryName = name + "_memory";
        segment = boost::interprocess::managed_shared_memory(boost::interprocess::open_only, memoryName.c_str());
        auto item = segment.find<T>((name + "_object").c_str());

        if (item.first == nullptr) {
            ThrowBalauException(
                Exception::NotFoundException, "The shared memory object with name prefix " + name + " was not found."
            );
        }

        object = item.first;
    }

    public: MSharedMemoryObject(OpenReadOnlySelector, const std::string & name) {
        const std::string memoryName = name + "_memory";
        segment = boost::interprocess::managed_shared_memory(boost::interprocess::open_read_only, memoryName.c_str());
        auto item = segment.find<T>((name + "_object").c_str());

        if (item.first == nullptr) {
            ThrowBalauException(
                Exception::NotFoundException, "The shared memory object with name prefix " + name + " was not found."
            );
        }

        object = item.first;
    }

    public: ~MSharedMemoryObject() {
        segment.destroy<T>((name + "_memory").c_str());
        boost::interprocess::shared_memory_object::remove((name + "_object").c_str());
    }

    public: MSharedMemoryObject(MSharedMemoryObject && rhs) noexcept
        : name(std::move(rhs.name))
        , segment(std::move(rhs.segment))
        , object(rhs.object) {
        rhs.object = nullptr;
    }

    public: MSharedMemoryObject & operator = (MSharedMemoryObject && rhs) noexcept {
        name = std::move(rhs.name);
        segment = std::move(rhs.segment);
        object = rhs.object;
        rhs.object = nullptr;
        return *this;
    }

    public: T * operator -> () {
        Assert::assertion(object != nullptr, "Attempt to dereference null object in shared memory object.");
        return object;
    }

    public: const T * operator -> () const {
        Assert::assertion(object != nullptr, "Attempt to dereference null object in shared memory object.");
        return object;
    }

    public: T & operator * () {
        Assert::assertion(object != nullptr, "Attempt to dereference null object in shared memory object.");
        return *object;
    }

    public: const T & operator * () const {
        Assert::assertion(object != nullptr, "Attempt to dereference null object in shared memory object.");
        return *object;
    }


    // Reserved memory for metadata/index used in the allocated block.
    private: static const size_t metadataOverhead = 512;

    private: std::string name;
    private: boost::interprocess::managed_shared_memory segment;
    private: T * object = nullptr;
};

} // namespace Balau::Interprocess

#endif // COM_BORA_SOFTWARE__BALAU_INTERPROCESS__MANAGED_SHARED_MEMORY_OBJECT