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Overview¶
protobluff is not the only C implementation for Protocol Buffers in the world, but it's actually one of the more recent ones. It has a different approach for handling messages than other libraries, like already described in the designal rationale.
This document compares protobluff to other Protocol Buffers implementations for the C language, in particular protobuf-c, nanopb, lwpb and pbc. Compared are only libraries that are not exclusively targeted at microcontrollers, but are designed for 32- and 64-bit systems.
Feature comparison¶
proto2¶
protobluff implements all features of the Protocol Buffers specification version 2 (known as proto2), except groups and generic services which are both deprecated. However, as Google is pushing out gRPC, there may be a gRPC-based service implementation in form of a plugin in the future. Below is a table showing the supported features of protobluff next to other Protocol Buffers libraries for C:
| Feature / Implementation | protobluff | protobuf-c | nanopb | lwpb | pbc |
|---|---|---|---|---|---|
| Message types | yes | yes | yes | yes | yes |
| Nested message types | yes | yes | yes | yes | yes |
| Cyclic message types | yes | yes | partial | yes | yes |
| Scalar types | yes | yes | yes | yes | yes |
| Default values | yes | yes | yes | yes | yes |
| Enumerations | yes | yes | yes | yes | yes |
| Extensions | yes | - | yes | - | yes |
| Oneofs | yes | yes | yes | - | - |
| Packages | yes | yes | yes | yes | yes |
| Packed option | yes | yes | yes | yes | yes |
| Deprecations | yes | partial | - | - | - |
In respect to the deprecation of generic services and groups, protobluff is the only library which is feature complete. nanopb is pretty close: it only misses deprecations and is inconvenient for working with cyclic messages. Furthermore, it's targeted at microcontrollers. protobuf-c doesn't support extensions and supports deprecations for fields only. lwpb and pbc seem inactive, as they don't support oneofs, a feature introduced in version 2.6.
Both, protobuf-c and lwpb provide a custom service implementation. However, the benefit is questionable, because the way messages are handled within a service may be highly application-dependent. Therefore, the solution proposed by both libraries may or may not be a good fit for your application. This is the reason why Google deprecated generic services and open sourced gRPC to provide a standard protocol for service interaction and integration.
proto3¶
The newest version of the Protocol Buffers specification is version 3 (known as proto3) which is wire-compatible with proto2. protobluff is basically compatible with proto3 – it will compile with the proto3 runtime, but it is not yet optimized for the new syntax.
The main features that need to be implemented for full proto3 support are maps and the Any type as a replacement for extensions, as well as some helper functions for working with the new set of default types and maybe the new JSON-mapping. However, the last two are of lower priority.
At the time of writing, none of the aforementioned alternative implementations supports proto3 yet.