Re: Yet Another Container: DynamicArray

From: Gavin Lambert (boost_at_[hidden])
Date: 2020-01-29 04:11:28

Mere moments ago, quoth I:
> On 25/01/2020 01:21, Glen Fernandes wrote:
>> Heap storage, fixed size at runtime:
>> Â Â Â  allocate_unique<T[]>(alloc, size, ...)
>>
>> Â  Gives users everything they need for buffers. (They don't need a 
>> Container that is copyable).
> 
> Not quite.  These keep the storage pointer and the storage size 
> separately, so you still need a wrapper type (such as the Asio buffer 
> types), or to keep passing them around separately (which is error-prone) 
> or to make assumptions instead of passing it around (which is very 
> error-prone).
> 
> C++20 introduces std::span, which is a good way of passing around a 
> pointer and size together -- but it's non-owning, so still isn't a 
> solution for the above.

To clarify: the Asio buffer types are also non-owning.

The need for an owning wrapper type is presumably what:

On 24/01/2020 21:44, Alexander Grund wrote:
> - Heap storage, fixed size at runtime: dynamic_array

was referring to (a type that contains a unique_ptr<T[]> and its size, 
or equivalent thereof), thus can act as an owning container.  (And you 
can then extract a span or Asio buffer from this, to then pass around 
without transferring ownership, or move the original container to 
transfer ownership.)

Though I'm not familiar with any existing standard/Boost implementation 
of this.  It probably is a thing that ought to exist.

(But that's a terrible name for a container that cannot change size.)