An efficient implementation of the Aho-Corasick string matching algorithm, compiled into a deterministic finite automaton (DFA). The code optimizes memory by using row-based state transitions and supports anchored patterns and wildcards. It is self-contained, with a clean public interface (struct SMACK and operations like smack_add_pattern, smack_compile, smack_search). This could be extracted as a standalone pattern-matching library for any application needing fast multi-pattern search.

Implements a Feistel network cipher based on DES S-boxes to create a pseudorandom permutation over an arbitrary range. This allows mapping a linear index to a shuffled IP:port combination deterministically. The code is isolated, with clear functions for initialization, shuffle, and unshuffle, and includes self-tests. It can be extracted as a reusable component for any scenario requiring efficient, repeatable random ordering of indices (e.g., load testing, data shuffling).

A lock-free multi-producer/multi-consumer ring buffer derived from Intel DPDK/FreeBSD. It uses atomic operations for head and tail indices, supporting concurrent enqueue and dequeue without locks. The implementation is a single header file with inline functions, making it easy to drop into other C projects. It is well-tested and demonstrates careful cache-line alignment and memory ordering.