zoo

zoo is a basic implementation of a plugin architecture in C++. I had originally created this for a segment of my dissertation work that I later dropped for being out of scope. Regardless, it was a valuable exercise in understanding loading and using symbols and creating generic APIs.

Logo from photo by Waldemar Brandt from Pexels

zoo overview

Plugins must comply with a basic API:

• A plugin called name must expose createName and destroyName
• createName must return a pointer to a new'd Name held by the plugin
  • Using a shared_ptr instead would be more C++
• destroyName must destroy an existing Name object
• Name objects must implement makeSound -- they are zoo animals after all

Plugins may be added to the designated plugins directory at any time, even while zoo is running. If added, plugins will be picked up and started on the fly.

building zoo

zoo uses the typical CMake build process. I have only tested it with GCC 5.4 and Clang 11.0, but it should work with any modern C++ compiler.

mkdir build
cd build
cmake ..
make
./zoo

zoo directory layout

Below is an example directory layout describing how each directory is designed to be used in the plugin architecture.

├── build
│   └── plugins               directory for installed plugins
├── CMakeLists.txt
├── doc                       directory for documentation
├── ext_plugins               directory for external (user defined) plugins
│   ├── cow.o
│   ├── plugins
│   │   ├── libcow.so
│   │   └── libzebra.so
│   ├── README                build instructions for external plugins
│   ├── src                   user-defined plugin sources
│   │   ├── cow.cpp
│   │   ├── cow.h
│   │   ├── zebra.cpp
│   │   └── zebra.h
│   └── zebra.o
├── include                   main include directory
│   └── animal.h              base abstract plugin class definition
├── plugins                   derived plugin class sources shipped with repo
│   ├── cat.cpp
│   ├── cat.h
│   ├── CMakeLists.txt        builds .so files for each derived plugin
│   ├── dog.cpp
│   ├── dog.h
│   ├── tiger.cpp
│   └── tiger.h
├── README                    this file
└── src                       main repo source
    ├── util                  utilities
    │   ├── globothy.cpp      glob files, used to find .so files
    │   ├── globothy.h
    │   ├── libnameothy.cpp   extract lib name from .so files
    │   └── libnameothy.h
    └── zoo.cpp               main(), runs two threads to find/call plugins