Mittelib

Nice C++17 goodies made in Mittelab

Repo: https://git.mittelab.org/proj/mittelib
Documentation: https://proj.mittelab.dev/mittelib/
PlatformIO lib: https://platformio.org/lib/show/12998/mitteLib

This library aim at providing some handy, general purpose functionalities to embedded development. The C++ STL is rich but some functionalities (e.g. std::variant) require features (e.g. CTTI) that are generally disabled on embedded platforms; other helper classes instead are common patterns when interoperating with C libraries. This was originally developed for ESP-IDF, in C++17, but it should be platform and framework independent (depending only on C++ 17). Among the added functionalities, binary streams, enum-based variants, and observer-pattern helper classes.

Using the library in your project

1. This library requires you to enable C++17 (or above) and is developed for ESP-IDF. If you are using another framework, e.g. Arduino, or a different C++ version, it might work, or it might not, but you are on your own.
2. Make sure you have enabled C++17. For ESP-IDF, this requires to unset C++11 and C++17. In your platformio.ini:

   [env:your_env]
   platform = espressif32
   framework = espidf

3. Check that your app compiles with these settings, first, using pio run or pio test. If it does,
4. add to platformio.ini the dependency on mitteLib:

   [env:your_env]
   ; ... all the above flags, plus:
   lib_deps = mittelab/mitteLib

5. You can now use mitteLib. The includes are in the subfolder mlab/, and the objects in the mlab namespace:

   {c++}
     #include <mlab/observable.hpp>
     
     // ...
     
     extern "C" void app_main() {
         mlab::observable<unsigned int> observable;
         // ...
     }

Developer guide

Folder structure

Important folders:

• mittelib/
  Library source code, divided in headers and source code.
  • mittelib/{include, src}/mlab/
    All sources are placed in the subfolder mlab. This reflects the namespace in which all the objects are located, and keeps the includes clean.
• tests/
  Subfolder containing the unit test projects.
  • tests/lib/mittelib/
    Symlink to mittelib/, to allow the unit tests to pick up the local library folder
  • tests/test/.keep
    We need to keep this folder for PlatformIO to believe we are providing unit test in our own custom entry point..

Secondary folders:

• cicd/ Helper files needed by CI/CD
• docs/ Doxygen config and additional doxygen sources
• misc/ Helper files needed for setting up development, logos, non-source material.

Setting up development

0. Install PlatformIO CLI.

1. Prepare tests/platformio.ini. You can, for example
   • Customize tests/platformio.ini.sample to your board and setup, or
   • Copy cicd/platformio.ini, the file used by CI/CD
2. Generate a compilation database for your IDE of choice using

   $> ./misc/gen-compiledb.py tests/platformio.ini       

   You have to regenerate this when a new file is added.
3. You are now using the unit test project to "host" the library (so you will see all usages of instantiated templates, for example).
4. Use the provided .clang-format file to format the source, e.g. by

   $> clang-format --style file -i mittelib/src/mlab/my_file.cpp

Running the tests

Note on the test project structure. We set up the unit test project in such a way that we can use both pio run and pio test to run the unit tests. The two commands are similar but different enough that some commands are available for one and not the other (for example, the compilation database is generated for pio run but not pio test). We work around this by providing a test transport (similar to the one provided by pio test), our own app_main() function and building sources and tests together.

0. Make sure you have setup your tests/platformio.ini as above.

1. Change directory and use either pio test or pio run, as follows:

   $> cd tests/
   $> pio run -t upload -t monitor  # or
   $> pio test

Building the documentation

1. Install Doxygen (or run through Docker), and run

   $> doxygen ./doxygen.conf

2. The documentation can be seen at ./docs/_build/html/index.html.