The header and write callback now uses a std::string_view as argument for data to avoid copying

[COM8]

Old

std::function<bool(std::string data, intptr_t userdata)> callback;

New

std::function<bool(const std::string_view& data, intptr_t userdata)> callback;

With the new way we avoid copying the payload.

[wonbinbk]

How does passing a string_view by reference can avoid copying the payload?

[COM8]

Every time you make a call to the following function data will be copied.

std::function<bool(std::string data, intptr_t userdata)> callback;

This means if e.g. data is multiple MB of size this copying is awfully inefficient.

If we now change it to const std::string_view& data best case we only "copy" 8 byte (on x86_64 systems) for the pointer we are using to access data.

[wonbinbk]

Should we pass string_view by value here instead of const&?

https://quuxplusone.github.io/blog/2021/11/09/pass-string-view-by-value/

Also it's worth to note that string_view depends on life time of the actual array it points too, since it's used in a constructor here, I think we should be careful about string life time as well.

Thanks for your time and effort on this library @COM8

[COM8]

I guess this was a classical case where I extremely successfully applied over optimization. Would you like to create a PR to convert const std::string_view& to std::string_view?