Re: A solution to return dynamic strings without heap allocation. Any interest?

From: Roberto Hinz (robhz786_at_[hidden])
Date: 2019-09-12 17:21:18

On Tue, Sep 10, 2019 at 11:05 PM Vinnie Falco <vinnie.falco_at_[hidden]>
wrote:

> `std::basic_ostream` is actually quite usable once you figure out how
> it works
>

Let me illustrate why I disagree with that. Suppose you want to
implement a base64 encoder. You want it to be fast, agnostic,
and simple to use. Now suppose you adopt `std::ostream` as
the destination type:

  void to_base64( std::ostream& dest, const std::byte* src, std::size_t
count );

You will face two issues:

1) It doesn't matter how well you (as the library author) understand
   basic_ostream. The *user* needs to implement derivates of
   basic_ostream to customize the destination types.

2) It's impossible to achieve a decent performance. If you used
   `outbuf` you could write directly into  the buffer. But with
   `std::ostream` you have to call member functions like `put`
   or `write` to for each little piece of the content, or to use an
   additional intermediate buffer.

And this is far to be a specific use case. The same issues apply
for any kind of encoding, binary or text.