C++ library like ASE

Perhaps a bit of a stretch for this category, but does anyone know of a C++ library that’s similar to ASE’s core functionality, i.e. atomic configurations, positions, cells, etc (no need for any calculator functionality)? Ideally something whose internal storage is compatible with the way one would use LAMMPS as a library, i.e. positions are stored in a float array in order x1y1z1x2y2z2…xNyNzN, etc.