buffer type naming and concept taxonomy

[sgerbino]

From the review result:

I'm unpersuaded that the current design handles the buffer abstractions and buffer concepts correctly. [...] the asio derived mutable and const buffer types become the foundation. [...] These two types are actually minimalist versions of std::span. [...]

 std::array<char, 1024> buf;
 auto buffer = capy::make_buffer( buf ); // make a view of the buffer not an actual buffer

[...] I'd be much happier if this api used the terms buffer_span or buffer_ref to clarify what the types mean. Even though that breaks from asio tradition the concept of a span was developed later.

The review also sketches dimensions a richer buffer concept set could express (storage, capacity, access, ownership, flow direction, range type, consumption, lifetime) and asks for this to be discussed in a separate mailing-list thread.

Source: Boost review result (conditional acceptance), Boost mailing list, September 2026.

Current state: mutable_buffer, const_buffer, and make_buffer are unchanged; the concept taxonomy recently moved in the opposite direction (the source/sink concept family was removed post-review, and #393/#396 already contest parts of that). This issue records the review item and will link the mailing-list thread once it starts; the direction should be settled there, not here.

[akrzemi1]

This item hinges on a more fundamental decision. In places where we believe ASIO got the wrong naming, can we afford to change the names to correctly describe the concepts, or is being a drop-in replacement a non-negotiable property?

Second, only because someone suggests useful additional tools should not be on itself enough to make that change. We have to know the motivation and the cost-to-benefit ration. The current buffer design is sufficient to make the streams work. This looks like a good balance.

[akrzemi1]

I can see that, unlike other names, buffer_length doesn't come from ASIO. Can we rename it? The names buffer_length and buffer_size are so similar, that they will get mixed. The former could be called either something uncommon, like buffer_num, or something very descriptive, like buffer_sequence_size.

[akrzemi1]

I also note that if you rename the function overloads from make_buffer to buffer_view, not only do you address the original concern, but also you make all the functions operating on buffers have prefix buffer_.