This might be duplicated to C CSV API for unicode, or How can I read and parse CSV files in C++?, but not exactly. The first one talks about a C library which has the potential to work but needs some code modification. The second one doesn't mention much about unicode support. I would rather open a new question instead of polluting the existing ones.
Since I am not an expert in i18n and unicode encoding stuff, I just wonder if there is such an library for C++ out-of-box?
Currently, my best effort is to call Python's csv parser in C++, which is pretty slow.