Armadillo is a C++ linear algebra library (matrix maths) aiming towards a good balance between speed and ease of use. The API is deliberately similar to Matlab's. Integer, floating point, and complex numbers are supported, as well as a subset of trigonometric and statistics functions. Various matrix decompositions are provided through optional integration with LAPACK and ATLAS numerics libraries. A delayed evaluation approach, based on template meta-programming, is used (during compile time) to combine several operations into one and reduce or eliminate the need for temporaries.
libxmp is a module player library which supports many mainstream and obscure module formats, including Protracker MOD, Scream Tracker III S3M, and Impulse Tracker IT. Possible applications for libxmp include standalone module players, module player plugins for other players, module information extractors, background music replayers for games and other applications, module-to-mp3 converters, etc.
HC-SR04 Ultrasonic Arduino Library is specifically for the HC-SR04 ultrasonic sensor. It features timing, metric conversion, and standard deviation methods, plus a few support methods. It is written in C++ to conserve the namespace. The conversion formula can be easily modified to optimize the accuracy of conversion at different distances for inches and centimeters. Multiple buffers of different lengths can be created for determining standard deviation.
MeteoIO is a C++ library whose main design goals are: providing meteorological data format/protocol independent data access; providing safe and robust I/O; making I/O code as unobtrusive and simple as possible for the user; providing ready to use data to the user (transparent caching, filtering, resampling, and spatial interpolation); enabling unattended use from an I/O point of view; offering high modularity so that individual elements of the library can easily be replaced/expanded/added; and by its modularity, help interdisciplinary development, each module being targeted at a specific developer profile.
The OATH Toolkit makes it easy to build one-time password authentication systems. It contains shared libraries, commandline tools, and a PAM module. Supported technologies include the event-based HOTP algorithm (RFC4226) and the time-based TOTP algorithm (RFC6238). OATH stands for Open AuTHentication, which is the organization which specifies the algorithms. For managing secret key files, the Portable Symmetric Key Container (PSKC) format described in RFC6030 is supported.
libusbx is a library which provides generic access to USB devices. As a library, it is meant to facilitate the development of applications which communicate with USB hardware. Its main features are portability (a single cross-platform API for Linux, OS X, Windows, and *BSD), user-mode (no special privileges required), and USB version-agnosticism (all versions of the protocol supported, including USB 3.0).