zfec is a fast, portable, and programmable implementation of erasure coding. It includes a C library, a Python library, and a command-line tool. Erasure coding is also known as "forward error correction", which is the generation of redundant blocks of information such that if some blocks are lost then the original data can be recovered from the remaining blocks. The RAID-5 algorithm is an erasure code, but while RAID-5 can recover from the loss of any one element, zfec can be parameterized to choose in advance the number of elements whose loss it can tolerate.
zlib is designed to be a free, general-purpose, legally unencumbered, lossless data-compression library for use on virtually any computer hardware and operating system. The zlib data format is itself portable across platforms. Unlike the LZW compression method used in Unix compress(1), the compression method currently used in zlib essentially never expands the data. (LZW can double or triple the file size in extreme cases.) zlib's memory footprint is also independent of the input data and can be reduced, if necessary, at some cost in compression.