How do I write a std::codecvt facet?

Question

How do I write a std::codecvt facet? I\'d like to write ones that go from UTF-16 to UTF-8, which go from UTF-16 to the systems current code page (windows, so CP_ACP), and to

Answer 1

The problem with this std::codecvt is it's a solution looking for a problem. Or rather, the problem it's trying to solve is unsolvable, so anybody trying to use it as a solution is going to be very disappointed.

If you don't know which character set your input or output is, then std::codecvt isn't ever going to be able to help you. Conversely, if you do know which character sets you're using, then you can trivially convert between them with a single function call. Wrapping that function call in a complicated mess of templates doesn't change those fundamentals.

...and that's why nobody uses std::codecvt. I recommend you just do what everybody else does, and pretend it never happened.