Re: [Boost-users] [Boost.Interprocess] int key and flat_multimap_index

From: Robert Kubrick (robertkubrick_at_[hidden])
Date: 2008-08-17 12:01:27

On Aug 17, 2008, at 5:15 AM, Ion Gaztañaga wrote:

> Robert Kubrick wrote:
>> A couple of beginner questions on basic_managed_heap_memory:
>> 1) I want to access elements in the contiguous memory segment by  
>> using an int key,  rather than a char string. Can I declare  
>> something like this:
>> typedef basic_managed_heap_memory <    int, /* my key is an  
>> integer */    rbtree_best_fit<null_mutex_family>,
>>    flat_map_index
>>    >  managed_heap_memory;
>> I need to lookup objects using an external integer ID but the ID  
>> can have any value (ie, does not match the 0-N array element order  
>> of my memory segment).
>
> No sorry, named allocation is only availables for chars. One  
> workaround thing you can do is to allocate anonymous objects in the  
> managed segment and create another map-like structure pointing to  
> those anonymous objects. More inefficient, I know, but I can't  
> think another way. Anyway, I think you've shown me a good use case  
> to study the possibility of using non-char indexes (something I  
> suspect will require a lot of work, because all the code supposes  
> string keys).
>
>> 2) If I want to insert multiple objects with the same char* name  
>> (ala multimap) can I create a flat_multimap_index?
>
> You can't. Names must be unique because it should identify a unique  
> named object. Otherwise, we wouldn't be capable to find an object  
> correctly.

A subset of objects could have the same name, but each object would  
be assigned to a unique slot in the segment. A multimap search on the  
non-unique name would return an equal_range object.

>
> Regards,
>
> Ion
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