Convert string to Unicode hex representation and back in C++

Convert string to Unicode hex representation and back in C++

I want to convert a string into a string which contains all characters of
the given string in their Unicode hex notation and back again. Target
language is C/C++.
For example, given the German word Hände, I want to be able to convert
this string into it's Unicode hex notation U+0068 U+00E4 U+006E U+0064
U+0065, and from it back to its original representation Hände.
How can this be accomplished?
Thank you!