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#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/containers/vector.hpp>
#include <boost/interprocess/allocators/allocator.hpp>
#include <boost/interprocess/containers/string.hpp>
#include <cstdlib> //std::system
#include <jsoncons/json.hpp>
#include <scoped_allocator>
using shmem_allocator = boost::interprocess::allocator<int,
boost::interprocess::managed_shared_memory::segment_manager>;
using cust_allocator = std::scoped_allocator_adaptor<shmem_allocator>;
struct boost_sorted_policy
{
template <typename KeyT,typename Json>
using object = jsoncons::sorted_json_object<KeyT,Json,boost::interprocess::vector>;
template <typename Json>
using array = jsoncons::json_array<Json,boost::interprocess::vector>;
template <typename CharT,typename CharTraits,typename Allocator>
using member_key = boost::interprocess::basic_string<CharT, CharTraits, Allocator>;
};
using cust_json = jsoncons::basic_json<char,boost_sorted_policy, cust_allocator>;
int main(int argc, char *argv[])
{
typedef std::pair<double, int> MyType;
if (argc == 1) // Parent process
{
//Remove shared memory on construction and destruction
struct shm_remove
{
shm_remove() { boost::interprocess::shared_memory_object::remove("MySharedMemory"); }
~shm_remove() noexcept { boost::interprocess::shared_memory_object::remove("MySharedMemory"); }
} remover;
//Construct managed shared memory
boost::interprocess::managed_shared_memory segment(boost::interprocess::create_only,
"MySharedMemory", 65536);
//Initialize shared memory STL-compatible allocator
const shmem_allocator alloc(segment.get_segment_manager());
// Create json value with all dynamic allocations in shared memory
cust_json* j = segment.construct<cust_json>("MyJson")(jsoncons::json_array_arg, alloc);
j->push_back(10);
cust_json o(jsoncons::json_object_arg, alloc);
o.try_emplace("category", "reference");
o.try_emplace("author", "Nigel Rees");
o.insert_or_assign("title", "Sayings of the Century");
o.insert_or_assign("price", 8.95);
j->push_back(o);
cust_json a(jsoncons::json_array_arg, 2, cust_json(jsoncons::json_object_arg, alloc),
jsoncons::semantic_tag::none, alloc);
a[0]["first"] = 1;
j->push_back(a);
std::pair<cust_json*, boost::interprocess::managed_shared_memory::size_type> res;
res = segment.find<cust_json>("MyJson");
std::cout << "Parent process:\n";
std::cout << pretty_print(*(res.first)) << "\n\n";
//Launch child process
std::string s(argv[0]); s += " child ";
if (0 != std::system(s.c_str()))
return 1;
//Check child has destroyed all objects
if (segment.find<MyType>("MyJson").first)
return 1;
}
else // Child process
{
//Open managed shared memory
boost::interprocess::managed_shared_memory segment(boost::interprocess::open_only,
"MySharedMemory");
std::pair<cust_json*, boost::interprocess::managed_shared_memory::size_type> res;
res = segment.find<cust_json>("MyJson");
if (res.first != nullptr)
{
std::cout << "Child process:\n";
std::cout << pretty_print(*(res.first)) << "\n";
}
else
{
std::cout << "Result is null\n";
}
//We're done, delete all the objects
segment.destroy<cust_json>("MyJson");
}
return 0;
}
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