The IPDR.org reference libraries encode and decode IPDR usage documents in either XML or the binary format. Libraries are available in C and Java.
FastGEO is a computational geometry library written in the object pascal language.
Midea is a robust c string api set with regex support, handling fixed width 8 to 64 bit character sets at runtime (no recompilation is required). Initialization routines convert multibyte encodings such as utf8.