Re: [boost] Proposal: Monotonic Containers

Subject: Re: [boost] Proposal: Monotonic Containers
From: Ion Gaztañaga (igaztanaga_at_[hidden])
Date: 2009-06-10 11:26:56

Christopher Jefferson wrote:

> Thanks!
> 
> No offence, but while that method is good as it is as general as 
> possible, it perhaps doesn't look very "C-like", and is maybe too 
> complex to try to pursade them to add.

Yes, it's not a proposal, it was just what I needed to add to implement 
C++ features.

> How important is backward expansion, and try_shrink_in_place? While 
> obviously these things are useful, do you think they are "vital"? I'm 
> interested as you have clearly written a lot of code which uses these 
> mechanisms.

Shrink in place is quite useful, because it offers no-throw trimming for 
containers like vector.

> My thought is that adding a function which is exactly "realloc, except 
> don't move, just return", with the option to try to get as much memory 
> as possible, say:
> 
> int realloc_try(void* ptr, size_t size, size_t* new_size)
> 
> With the same semantics as relloc except it doesn't move, and if it can 
> do a partial expansion (or shrink) tries to do as much as it can and 
> returns the new size in new_size, is (from looking at source) a very 
> easy addition to many mallocs, and less invasive.

It's an alternative, the advantage of a possible allocation is that the 
internal mutex and memory algorithm security checks are performed only once.

> Chris

Another note: containers that implement this also support stateful 
allocators so they can be used also for your proposed arena-like allocators.

Best,

Ion