SEIN Parser

Very lightweight single-file config parser in .ini style for C++17/C11/Python

Capabilities:
No external dependencies
File reading via mmap (POSIX and Windows) – no unnecessary copying through the kernel
Lock-free hot paths in C (_Atomic counters, acquire/release)
std::from_chars in C++ - no allocations and exceptions when parsing numbers
Background parsing in a thread (pthreads/std::thread/Python threading)
Recognition of bool case-insensitively (true/yes/1, false/no/0)
Safe default values in all getters