Add StringView template typename to basic_json

[dv1]

Currently, basic_json expects one string type, which is used for everything - arguments, temporary strings, etc. This may be inefficient if data is available as some sort of a "string view". For example, if a C API offers a const char* value and a length integer, then it is possible to wrap these in a boost::string_ref instance. Since the JSON parser does not modify the source string, it would be possible to allow for specifying something like boost::string_ref as a "StringView" template typename, and std::string as a "String" type, which is then used internally.

The net gain is that a copy is avoided. In the example mentioned above, I have to create a temporary std::string and do a copy of the source string. With a StringView typename, I could avoid that copy.

[nlohmann]

I don't fully understand. Where exactly would this be added?

[dv1]

I'd add a json::parse() overload that accepts string views.

EDIT: Related: a templated parse() variant that passes through universal references would also be useful. See for example this article about perfect forwarding and universal references.

[nlohmann]

I need more information on this to assess whether and how to extend the library.