llrb.h is an iterative implementation of Robert Sedgewick's 2-3 variant left-leaning red-black tree algorithm. It's written to be a drop-in replacement for Niels Provos' <sys/tree.h> C preprocessor red-black tree library.
Open source project that offer summary and download services on this page is a project that carry out their development work on other open source development sites. Their work is linked to this page via a feature called OFI, and their work is not carried out here on OSDN site.