String Theory is a flexible modern C++ library for string manipulation
and storage.  It stores data internally as UTF-8, for ease of use
with existing C/C++ APIs.  It can also handle conversion to and
from UTF-16, UTF-32, and Latin-1, and has a variety of methods to
simplify text manipulation.

In addition, String Theory includes a powerful and fast type-safe
string formatter (ST::format), which can be extended with custom
type formatters by end-user code.

WWW: https://github.com/zrax/string_theory