Update DataStorm strings

[bernardnormier]

This PR updates the DataStorm to use string (copies) instead of const string& where appropriate.

[bernardnormier]

Keep in mind that even if the caller keeps his string (neglects to move it), the performance is identical - the previous code was copying this string.

[bernardnormier]

The focus of this PR was strings. It's possible other parameters should be by value too.

[bernardnormier]

We need a more systematic cleanup in a follow-up PR for final / override and similar.

[pepone]

Do you mean the std::regex constructor? We don't pass criteria to regex_match

[bernardnormier]

Here is the full code:

        // std::regex_match accepts a const string&.
        return [](const std::string& criteria)
        {
            std::regex expr(criteria);
            return [expr](const Value& value)
            {
                std::ostringstream os;
                os << value;
                return std::regex_match(os.str(), expr);
            };
        };

[pepone]

Value can be anything that defines << osstream operator, it doesn't have to be a string.

For the regex constructor can we use 8 https://en.cppreference.com/w/cpp/regex/basic_regex/basic_regex

And do:

return [](std::string criteria)
        {
            std::regex expr(std::move(criteria));

I think the complication here is this template factory are used for different things and, pass by value might be not supported for all usages.

[bernardnormier]

What I meant with this comment is a typical regex filter function - regex_match - accepts a const string& and not a string_view (which in theory it could), and as a result it's ok/reasonable for our makeRegexFilter function to return a function that accepts a const string& and not a string_view.

basic_regex does not provide a constructor with string parameter. I don't see how (8) would work with:

std::regex expr(std::move(criteria));

I think you would still get (6).

In any case, I'll update to comment to refer to the regex constructor.