FOXXLL is a C++ library for asynchronous I/O and block management. It is used by STXXL and Thrill for external memory support.

FOXXLL usually opens one big file and the user program then allocates regularly-sized blocks inside the file. These blocks can then be read/written using asynchronous operations. This is the basic layer for many large data structures or stream processing algorithms.

See STXXL for more information of external memory algorithms: https://stxxl.org

And Thrill for distributed (external) memory processing: http://project-thrill.org