Add label_override field option

This lets proto3 files define submessage fields which nanopb treats as
required (even though proto3 doesn't support 'required'). This means that
nanopb won't generate a has_xxx field, will reject messages where this
field is missing, and will always serialize the field. However, other
consumers of the proto file won't see the field as required, and are
therefore safe to it being removed in future.

To do this, use:

    Submessage some_submessage = 1 [(nanopb).label_override = LABEL_REQUIRED];

This mechanism also lets users change whether nanopb treats the field as
optional or repeated in both proto2 and proto3.

Fixes: #962
4 files changed
tree: 9fdbc4cbfe00fda4e711c21a8465c65fdc08d65f
  1. .github/
  2. build-tests/
  3. conan-wrapper/
  4. docs/
  5. examples/
  6. extra/
  7. generator/
  8. spm-test/
  9. spm_headers/
  10. spm_resources/
  11. tests/
  12. tools/
  13. zephyr/
  14. .bazelignore
  15. .gitattributes
  16. .gitignore
  17. AUTHORS.txt
  18. BUILD.bazel
  19. build.py
  20. CHANGELOG.txt
  21. CMakeLists.txt
  22. conanfile.py
  23. CONTRIBUTING.md
  24. library.json
  25. LICENSE.txt
  26. MODULE.bazel
  27. MODULE.bazel.lock
  28. Package.swift
  29. pb.h
  30. pb_common.c
  31. pb_common.h
  32. pb_decode.c
  33. pb_decode.h
  34. pb_encode.c
  35. pb_encode.h
  36. README.md
  37. requirements.txt
  38. WORKSPACE
README.md

Nanopb - Protocol Buffers for Embedded Systems

Latest change Weekly build

Nanopb is a small code-size Protocol Buffers implementation in ansi C. It is especially suitable for use in microcontrollers, but fits any memory restricted system.

Using the nanopb library

To use the nanopb library, you need to do two things:

  1. Compile your .proto files for nanopb, using protoc.
  2. Include pb_encode.c, pb_decode.c and pb_common.c in your project.

The easiest way to get started is to study the project in “examples/simple”. It contains a Makefile, which should work directly under most Linux systems. However, for any other kind of build system, see the manual steps in README.txt in that folder.

Generating the headers

Protocol Buffers messages are defined in a .proto file, which follows a standard format that is compatible with all Protocol Buffers libraries. To use it with nanopb, you need to generate .pb.c and .pb.h files from it:

python generator/nanopb_generator.py myprotocol.proto  # For source checkout
generator-bin/nanopb_generator myprotocol.proto        # For binary package

(Note: For instructions for nanopb-0.3.9.x and older, see the documentation of that particular version here)

The binary packages for Windows, Linux and Mac OS X should contain all necessary dependencies, including Python, python-protobuf library and protoc. If you are using a git checkout or a plain source distribution, you will need to install Python separately. Once you have Python, you can install the other dependencies with pip install --upgrade protobuf grpcio-tools.

You can further customize the header generation by creating an .options file. See documentation for details.

Running the tests

If you want to perform further development of the nanopb core, or to verify its functionality using your compiler and platform, you'll want to run the test suite. The build rules for the test suite are implemented using Scons, so you need to have that installed (ex: sudo apt install scons or pip install scons). To run the tests:

cd tests
scons

This will show the progress of various test cases. If the output does not end in an error, the test cases were successful.

Note: Mac OS X by default aliases ‘clang’ as ‘gcc’, while not actually supporting the same command line options as gcc does. To run tests on Mac OS X, use: scons CC=clang CXX=clang++. Same way can be used to run tests with different compilers on any platform.

For embedded platforms, there is currently support for running the tests on STM32 discovery board and simavr AVR simulator. Use scons PLATFORM=STM32 and scons PLATFORM=AVR to run these tests.

Build systems and integration

Nanopb C code itself is designed to be portable and easy to build on any platform. Often the bigger hurdle is running the generator which takes in the .proto files and outputs .pb.c definitions.

There exist build rules for several systems:

And also integration to platform interfaces: