Re: [Boost-users] [interprocess] Container

Subject: Re: [Boost-users] [interprocess] Container
From: Moritz (mokoman_at_[hidden])
Date: 2009-07-09 15:24:38

> is there a possibility to put something like this into the shared_memory?
> 
> class A
> {
>   int a;
>   double d;
>   // ...
>   boost::interprocess string s;
> }

I need to save classes in the managed_shared_memory that contain strings 
and vectors and all that stuff.
So the general way to put a string into the shared_mem is like this:

typedef boost::interprocess::allocator<char, 
boost::interprocess::managed_shared_memory::segment_manager> CharAllocator;
typedef boost::interprocess::basic_string<char, std::char_traits<char>, 
CharAllocator> string;

string *s = managed_shm.find_or_construct<string>("String")("bla", 
managed_shm.get_segment_manager());

So I now want to save a class that contains a string. Therefore I wanted 
  to use a class like this:

class A
{
public:
A(boost::interprocess::managed_shared_memory::segment_manager *seg)
  : calloc(seg), s(calloc)
{};

CharAllocator calloc;
string s;
}

and then I wanted to do something like this:
A *a = 
managed_shm.find_or_construct<A>("name")(managed_shm.get_segment_manager());
//to save in the shared_mem

BUT for some reason the = operator of allocator is private. The first 
question is now if there is a general way to save a class like this in 
the shared_memory.

And if so, the second question is how I can create an instance of this 
class that does _not_ allocate memory from the shared_memory (for 
purposes of the process that writes to the shared_mem). To write to the 
shared_mem I just want to say:

(*a) = anotherA;

where anotherA is an instance from A that does not allocate memory from 
the shared memory.

I hope it is not too confusing.

Thanks in advance
Best regards,
Moritz