boost - 如何创建进程间容器的 boost 进程间向量？

Question

我喜欢创建包含进程间容器的类的 boost 进程间向量。以下代码在调整大小函数调用之前一直有效，当然是因为我的类没有默认构造函数。我该如何解决这个问题？该示例基于 boost Containers of containers例子

谢谢马库斯

#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/allocators/allocator.hpp>
#include <boost/interprocess/containers/map.hpp>
#include <boost/interprocess/containers/vector.hpp>
#include <boost/interprocess/containers/string.hpp>

using namespace boost::interprocess;

//Typedefs of allocators and containers
typedef managed_shared_memory::segment_manager                       segment_manager_t;
typedef allocator<void, segment_manager_t>                           void_allocator;
typedef allocator<int, segment_manager_t>                            int_allocator;
typedef vector<int, int_allocator>                                   int_vector;
typedef allocator<char, segment_manager_t>                           char_allocator;
typedef basic_string<char, std::char_traits<char>, char_allocator>   char_string;

class complex_data
{
public:
   int               id_;
   char_string       char_string_;
   int_vector int_vector_;

   //Since void_allocator is convertible to any other allocator<T>, we can simplify
   //the initialization taking just one allocator for all inner containers.
   complex_data(const void_allocator &void_alloc)
      : id_(-1), char_string_(void_alloc), int_vector_(void_alloc)
   {}
   //Other members...
};


typedef allocator<complex_data, segment_manager_t>     complex_data_allocator;
typedef vector<complex_data, complex_data_allocator>   complex_data_vector;

int main ()
{
   //Remove shared memory on construction and destruction
   struct shm_remove
   {
      shm_remove() { shared_memory_object::remove("MySharedMemory"); }
      ~shm_remove(){ shared_memory_object::remove("MySharedMemory"); }
   } remover;

   //Create shared memory
   managed_shared_memory segment(create_only,"MySharedMemory", 65536);

   //An allocator convertible to any allocator<T, segment_manager_t> type
   void_allocator alloc_inst (segment.get_segment_manager());

   //Construct the shared memory map and fill it
   complex_data *complex_data0_ = segment.construct<complex_data> ("MyCompexData")(alloc_inst);

   complex_data0_->char_string_ = "Hello Wold";
   complex_data0_->int_vector_.push_back(3);

   complex_data *complex_data1_ = segment.find_or_construct<complex_data> ("MyCompexData")(alloc_inst);
   complex_data1_->int_vector_.push_back(6);

   std::cout << complex_data1_->id_ << ", " << complex_data0_->char_string_;
   for(size_t i = 0; i < complex_data1_->int_vector_.size(); i++) std::cout << ", " << complex_data1_->int_vector_[i];


   complex_data_vector *complex_data_vector0 = segment.construct<complex_data_vector> ("MyCompexDataVector")(alloc_inst);

   /**
    * Problem
    * How to I resize or add new elements?
    **/
   complex_data_vector0->resize(3);  


   return 0;
}

Answer 1

重写

由于 Boost Containers 支持作用域分配器模式，您可以只使用作用域分配器，并且当该元素具有 uses_allocator<> 时，容器会自动将其传递给新元素的内部构造(或放置)。特质积极地专门化它:

Live On Coliru

#include <boost/interprocess/managed_shared_memory.hpp>
#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/containers/string.hpp>

using namespace boost::interprocess;

//Typedefs of allocators and containers
typedef managed_shared_memory::segment_manager                       segment_manager_t;
typedef boost::container::scoped_allocator_adaptor<allocator<void, segment_manager_t> >
                                                                     void_allocator;
typedef void_allocator::rebind<int>::other                           int_allocator;
typedef vector<int, int_allocator>                                   int_vector;

typedef void_allocator::rebind<char>::other                          char_allocator;
typedef basic_string<char, std::char_traits<char>, char_allocator>   char_string;

class complex_data
{
public:
   int               id_;
   char_string       char_string_;
   int_vector int_vector_;

   //Since void_allocator is convertible to any other allocator<T>, we can simplify
   //the initialization taking just one allocator for all inner containers.
   typedef void_allocator allocator_type;

   complex_data(complex_data const& other, const allocator_type &void_alloc)
       : id_(other.id_), char_string_(other.char_string_, void_alloc), int_vector_(other.int_vector_, void_alloc)
   {}
   complex_data(const allocator_type &void_alloc)
      : id_(-1), char_string_(void_alloc), int_vector_(void_alloc)
   {}
   //Other members...
   //
};

typedef void_allocator::rebind<complex_data>::other    complex_data_allocator;
typedef vector<complex_data, complex_data_allocator>   complex_data_vector;

int main ()
{
   //Remove shared memory on construction and destruction
   struct shm_remove
   {
      shm_remove() { shared_memory_object::remove("MySharedMemory"); }
      ~shm_remove(){ shared_memory_object::remove("MySharedMemory"); }
   } remover;

   //Create shared memory
   managed_shared_memory segment(create_only,"MySharedMemory", 65536);

   //An allocator convertible to any allocator<T, segment_manager_t> type
   void_allocator alloc_inst (segment.get_segment_manager());

   //Construct the shared memory map and fill it
   complex_data *complex_data0_ = segment.construct<complex_data> ("MyCompexData")(alloc_inst);

   complex_data0_->char_string_ = "Hello Wold";
   complex_data0_->int_vector_.push_back(3);

   complex_data *complex_data1_ = segment.find_or_construct<complex_data> ("MyCompexData")(alloc_inst);
   complex_data1_->int_vector_.push_back(6);

   std::cout << complex_data1_->id_ << ", " << complex_data0_->char_string_;
   for(size_t i = 0; i < complex_data1_->int_vector_.size(); i++) std::cout << ", " << complex_data1_->int_vector_[i];


   complex_data_vector *complex_data_vector0 = segment.construct<complex_data_vector> ("MyCompexDataVector")(alloc_inst);

   complex_data_vector0->resize(3);
   complex_data_vector0->emplace_back();
}

请注意我是如何重新绑定(bind) void_allocator 的分配器定义的类型，使更改代码的“根分配器”实现变得更加容易。