Subject: Re: [boost] [interprocess] map of vectors
From: Jan Stetka (janpstetka_at_[hidden])
Date: 2008-11-30 08:30:29
Ion Gaztañaga wrote:
> Jan Stetka wrote:
>> Hi,
>>
>> Is something like this likely to work?
>>
>> typedef interprocess::vector<int, ShmemAllocator> MyVector
>>
>> typedef std::pair<const long, MyVector> ValueType;
>>
>> typedef allocator<ValueType,
>> managed_shared_memory::segment_manager> ShmemAllocator;
>>
>> typedef interprocess::map<long, MyVector, std::less<long>,
>> ShmemAllocator> MyMap;
>
> Yes, it should:
>
> #include <boost/interprocess/containers/vector.hpp>
> #include <boost/interprocess/containers/map.hpp>
> #include <boost/interprocess/managed_shared_memory.hpp>
>
> using namespace boost::interprocess;
>
> typedef managed_shared_memory::segment_manager Mngr;
>
> typedef allocator<int, Mngr> ShmemIntAllocator;
> typedef vector<int, ShmemIntAllocator> MyVector;
> typedef std::pair<const long, MyVector>ValueType;
> typedef allocator<ValueType, Mngr> ShmemValueTypeAllocator;
> typedef map<long, MyVector
> , std::less<long>, ShmemValueTypeAllocator> MyMap;
>
> int main()
> {
> {
> shared_memory_object::remove("name");
> managed_shared_memory shmem(open_or_create, "name", 65536);
>
> MyMap *m = shmem.construct<MyMap>("Map name")
> (std::less<long>(), shmem.get_segment_manager());
>
> //This is the usual way
> ValueType v(0, MyVector(shmem.get_segment_manager()));
> m->insert(v);
> //This is more efficient(data is moved instead of copied)
> //Note that "long" is not "const long"
> std::pair<long, MyVector> mv
> (1, MyVector(shmem.get_segment_manager()));
> m->insert(move(mv));
>
> //Even more efficient, in-place construction:
> //the first argument is for the key (long),
> //the rest are for the mapped type
> m->emplace(2, shmem.get_segment_manager());
> }
> shared_memory_object::remove("name");
> return 0;
> }
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Does every instance of a container need its own segment?