c++ - 将进程间包装器 boost 到分配器

Question

我在共享内存中有多个索引容器

//Create hash
typedef boost::multi_index::multi_index_container<
  My_Key,
  My_Key_hash_indices,
  bip::allocator<MyKey, bip::managed_shared_memory::segment_manager>
> MyGlobalHash;

我需要根据配置使用以下之一:

1. bip::managed_mapped_file
2. bip::managed_shared_memory

有没有办法在不创建这两种类型的情况下做到这一点，比如为分配器创建一个包装类并为这两种类型继承。

更多代码在 http://coliru.stacked-crooked.com/a/09ea79752512fad8

Answer 1

不，你不需要那个。一个快速的静态断言得知默认的段管理器类型是相同的:

static_assert(std::is_same<
        bip::managed_shared_memory::segment_manager,
        bip::managed_mapped_file::segment_manager>{}, "incompatible segments");

所以，你可以只使用一个:

using SegmentManager = bip::managed_shared_memory::segment_manager;

演示

Live On Coliru

#include <iostream>
#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/managed_mapped_file.hpp>
#include <boost/interprocess/allocators/allocator.hpp>

namespace bip = boost::interprocess;

static_assert(std::is_same<
        bip::managed_shared_memory::segment_manager,
        bip::managed_mapped_file::segment_manager>{}, "incompatible segments");
using SegmentManager = bip::managed_shared_memory::segment_manager;

struct X {
    int i = 0;
};

#include <boost/multi_index_container.hpp>
#include <boost/multi_index/member.hpp>
#include <boost/multi_index/ordered_index.hpp>

namespace bmi = boost::multi_index;

using Table = bmi::multi_index_container<X,
      bmi::indexed_by< bmi::ordered_unique< bmi::tag<struct byI>, bmi::member<X, int, &X::i> > >,
      bip::allocator<X, SegmentManager>
  >;

void dump(Table const& t) {
    std::cout << "table: ";
    for(auto& x : t)
        std::cout << x.i << "; ";
    std::cout << std::endl;
}

void run_test(Table& table) {
    dump(table);

    if (table.empty()) {
        table.insert({{1}, {2}, {3}, {4}});
    } else {
        table.insert({5});
    }

    dump(table);

    table.erase(table.begin());
    dump(table);
}

int main() {
    {
        bip::managed_shared_memory segment(bip::open_or_create, "msm", 10ul<<20);
        run_test(*segment.template find_or_construct<Table>("name")(segment.get_segment_manager()));
    }
    {
        bip::managed_mapped_file segment(bip::open_or_create, "mmf", 10ul<<20);
        run_test(*segment.template find_or_construct<Table>("name")(segment.get_segment_manager()));
    }
}

打印(在我的系统上)例如:

table: 2; 3; 4; 
table: 2; 3; 4; 5; 
table: 3; 4; 5; 
table: 2; 3; 4; 
table: 2; 3; 4; 5; 
table: 3; 4; 5;