One of the more important but somewhat mysterious aspects of hashtables is writing hash functions. A hash function needs to take your data (possibly fixed-size, possibly variable-sized) and turn it into a fixed-size number that has “good distribution”. If you manage this, you won’t get a lot of collisions. This means each hash lookup will have to look at only a few buckets in the table and so will be fast.
The Apache Portable Runtime (APR) is a supporting library for the Apache web server. It provides a set of APIs that map to the underlying operating system. Where the OS doesn’t support a particular function, APR will provide a replacement. Thus, the APR can be used to make a program truly portable across platforms.
The Apache C++ Standard Library project (code name stdcxx, pronounced “standard C++ library”, not S-T-D-C-X-X) is a collection of algorithms, containers, iterators, and other fundamental components of every piece of software, implemented as C++ classes, templates, and functions essential for writing C++ programs.