Re: [boost] [interprocess][multi_index] emplace() is not sufficient for maps

Subject: Re: [boost] [interprocess][multi_index] emplace() is not sufficient for maps
From: Thorsten Ottosen (thorsten.ottosen_at_[hidden])
Date: 2009-09-24 11:23:43

Howard Hinnant skrev:
> On Sep 24, 2009, at 10:02 AM, Thorsten Ottosen wrote:

>> It doesn't quite address my first issue though, namely that I need to 
>> construct the mapped value in the node, and then compute the key from 
>> this mapped value (after some modification).
>>
>> I think if the node_ptr class had
>>
>> a) a forwarding (Key,Value) constructor
>>
>> b) an emplacing constructor that
>> constructed the pair with (Key,...)
>>
>> then I could do exactly what I needed :-)
> 
> With what allocator would the node_ptr allocate the node?
> 

Ok, I guess that is why I originally spoke about the following interface:

   typedef ... map;
   map m;
   map::node_ptr p = m.get_node_ptr(<like emplace, but only for
                                    constructing the mapped value>);
   p->pair.first = modify( p->pair.second );
   m.insert( boost::move(p) );

So get_node_ptr( ... ) with two overloads would be needed.

-Thorsten