Apache Portable Runtime (APR) Library

The mission of the Apache Portable Runtime (APR) project is to create
and maintain software libraries that provide a predictable and
consistent interface to underlying platform-specific implementations.
The primary goal is to provide an API to which software developers may
code and be assured of predictable if not identical behaviour
regardless of the platform on which their software is built, relieving
them of the need to code special-case conditions to work around or take
advantage of platform-specific deficiencies or features.

The APR is used by both Open Source and Commercial projects, prominent
examples being the Apache HTTP server.