Re: [boost] Proposal: Monotonic Containers

Subject: Re: [boost] Proposal: Monotonic Containers
From: Thorsten Ottosen (thorsten.ottosen_at_[hidden])
Date: 2009-06-10 17:08:10

Christopher Jefferson skrev:

> Very interesting. I have been working on a similar, but much more 
> limited, proposal which just does this for vector.
> 
> I decided I had to implement a new class, because building on top of the 
> 'allocator' framework wasn't sensible, because you waste too much buffer 
> space. For example, I believe your example won't work. I'd be interested 
> to see what you think.
> 
> Consider your example, in g++ (which I know how it operates internally)
> 
> boost::monotonic::inline_storage<100*sizeof(Object)> storage; // create 
> local storage on the stack boost::monotonic::vector<Object> 
> deathrow(storage); // create a std::vector that uses this storage
> foreach (object in world)
>  { if (IsDead(object)) deathrow.push_back(object); // allocation is just 
> advancing a pointer }
> 
> 
> This will build a vector which will continuously expand, through sizes 
> 1,2,4,8,16,32. At each step, it will allocate a new block of memory and 
> free the old one, making the storage size 1,3,7,15,31,63. When we try to 
> push_back beyond 32 elements, the next allocation will overflow the buffer.
> 
> Am I missing something?

Maybe

http://www.cs.aau.dk/~nesotto/boost/trunk/libs/auto_buffer/doc/html/
http://www.cs.aau.dk/~nesotto/boost/trunk/boost/auto_buffer/

is what you are looking for?

-Thorsten