Boost regexp how to translate such PHP unescape function to C++?

Question

Whe I had to create CMS in PHP I created simple unescape html function that looked like this:

function unescape($s) {
    $s= preg_replace('/%u(....)/', '&#x$1;', $s);
    $s= preg_replace('/%(..)/', '&#x$1;', $s);
return $s;
}

How to translate it into C++ using Boost.Regex?

Answer 1

I'd guess it would look a bit like this:

std::string unescape(const std::string s)
{
  std::string temp = boost::regex_replace(s, "%u(....)", "&#x$1;", boost::match_default);
  temp = boost::regex_replace(temp, "%u(..)", "&#x$1;", boost::match_default);
  return temp;
}

But I assume the . (DOT) should only match hexadecimal values, in which case I'd go for something like this instead:

std::string unescape(const std::string s)
{
  return boost::regex_replace(s, "%u([0-9a-fA-F]{2}|[0-9a-fA-F]{4})", "&#x$1;",
                              boost::match_default);
}

(note that I did not test this!)