Parsing from std::string_view

[GoldsteinE]

Currently e.g. rfl::json provides two ways to parse a string: from std::string or from std::istream (where the second delegates to the first). That means that parsing from std::string_view currently requires an allocation. yyjson_read() doesn’t take ownership of the passed string, so parsing directly from std::string_view should be possible unless I’m missing something.

I think the same holds for other formats, but I only checked yyjson and pugixml.

[liuzicheng1987]

@GoldsteinE , true, none of the formats support std::string_view. But it would be a good idea and should be fairly easy to implement.