在对象的构造函数中打开 Boost 进程间段

答案有很多组成部分：

• 使用简化的类型别名
• 该区段必须保持映射状态，因此您必须将其作为类中的成员（或具有更长的生存期）
• 只有当一致地使用作用域分配器并且插入使用分配器构造（例如 方法）emplace

我在使用 Boost Container 的实现方面有很好的经验，所以让我们展示一下。

简化的类型别名

// Typedefs for shared data structures
namespace bip = boost::interprocess;

namespace Shared {
    namespace bc  = boost::container;
    using Segment = bip::managed_shared_memory;
    using Mgr     = Segment::segment_manager;

    template <typename T> using Alloc  = bc::scoped_allocator_adaptor<bip::allocator<T, Mgr>>;
    template <typename T> using Vector = bc::vector<T, Alloc<T>>;
    template <typename K, typename V, typename Cmp = std::less<K>, typename P = std::pair<K const, V>>
    using Map = bc::map<K, V, Cmp, Alloc<P>>;
} // namespace Shared

现在您可以简单地声明：

using IVMap = Shared::Map<int, Shared::Vector<int>>; // Int_Vector_Map

它将扩展到正确的比较器、分配器等。

辈子

若要从构造函数构造段，需要使用初始值设定项列表。例如：

class Communication {
  public:
    Communication() //
        : segment_{bip::open_only, "Shared"}
        , map_(*segment_.find<IVMap>("Map").first) {}

    void addData(int key, int value);

  private:
    Shared::Segment segment_;
    IVMap&          map_;
};

Emplace（安居酒店）

要插入新元素，请实现如下：addData

void addData(int key, int value) {
    auto it = map_.find(key);

    if (it == map_.end())
        it = map_.emplace(key).first;

    it->second.push_back(value);
}

请注意，该区段仅存在。请注意，分配器是由于作用域分配器适配器与结构相结合而传播的。emplace

编辑可悲的是，我无法使 emplace 编译。我敢肯定我错过了一些微不足道的东西，但我已经解决了它，比如：

if (it == map_.end()) {
    IVMap::mapped_type v(map_.get_allocator());
    it = map_.emplace(key, std::move(v)).first;
}

现场演示

在 Coliru 上直播

#include <boost/container/scoped_allocator.hpp>
#include <boost/interprocess/allocators/allocator.hpp>
#include <boost/interprocess/containers/map.hpp>
#include <boost/interprocess/containers/vector.hpp>
#include <boost/interprocess/managed_mapped_file.hpp>
#include <boost/interprocess/managed_shared_memory.hpp>
#include <set>

// Typedefs for shared data structures
namespace bip = boost::interprocess;

namespace Shared {
    namespace bc  = boost::container;
#ifdef COLIRU // online compiler
    using Segment = bip::managed_mapped_file;
#else
    using Segment = bip::managed_shared_memory;
#endif
    using Mgr     = Segment::segment_manager;

    template <typename T> using Alloc  = bc::scoped_allocator_adaptor<bip::allocator<T, Mgr>>;
    template <typename T> using Vector = bc::vector<T, Alloc<T>>;
    template <typename K, typename V, typename Cmp = std::less<K>, typename P = std::pair<K const, V>>
    using Map = bc::map<K, V, Cmp, Alloc<P>>;
} // namespace Shared

using IVMap = Shared::Map<int, Shared::Vector<int>>; // Int_Vector_Map

class Communication {
  public:
    Communication() //
        : segment_{bip::open_only, "Shared"}
        , map_(*segment_.find<IVMap>("Map").first) {}

    void addData(int key, int value) {
        auto it = map_.find(key);

        if (it == map_.end()) {
            IVMap::mapped_type v(map_.get_allocator());
            it = map_.emplace(key, std::move(v)).first;
        }

        it->second.push_back(value);
    }

    auto const& get() const { return map_; }

  private:
    Shared::Segment segment_;
    IVMap&          map_;
};

#include <fmt/ranges.h>
#include <functional>
#include <random>
static auto vals = bind(std::uniform_int_distribution(100, 999), std::mt19937{std::random_device{}()});

int main(int argc, char** argv) {
    auto const args = std::set<std::string_view>(argv + 1, argv + argc);

    if (args.contains("parent")) {
        Shared::Segment seg{bip::open_or_create, "Shared", 10 << 10};
        seg.find_or_construct<IVMap>("Map")(seg.get_segment_manager());
    }

    if (args.contains("child")) {
        Communication comm;

        for (unsigned n = 10; n--;) {
            auto v = vals();
            comm.addData(v / 100, v);
        }

        fmt::print("After insertion:\n - {}\n", fmt::join(comm.get(), "\n - "));
    }
}

印刷

+ ./a.out parent
+ ./a.out child
After insertion:
 - (1, [155, 170])
 - (2, [248])
 - (4, [418])
 - (5, [542, 562])
 - (6, [642, 674, 659])
 - (7, [783])
+ ./a.out child
After insertion:
 - (1, [155, 170, 143, 130])
 - (2, [248, 222])
 - (3, [325])
 - (4, [418, 428])
 - (5, [542, 562, 556])
 - (6, [642, 674, 659, 671])
 - (7, [783, 793, 733, 745])
+ ./a.out child
After insertion:
 - (1, [155, 170, 143, 130])
 - (2, [248, 222])
 - (3, [325, 320, 362])
 - (4, [418, 428, 486, 437])
 - (5, [542, 562, 556])
 - (6, [642, 674, 659, 671, 695, 609])
 - (7, [783, 793, 733, 745, 786, 777, 793])
 - (9, [995])

本地现场演示：