C3 Protobuf

A lightweight, native Protocol Buffers (proto3) implementation for the C3 programming language.

Features

• Proto3 Support: Adheres to proto3 semantics (e.g., default values omitted from wire).
• Core Types: Supports Varints, 32/64-bit fixed types, strings, bytes, and nested messages.
• Packed Fields: Efficient encoding/decoding for repeated primitive fields.
• Memory Efficient: Uses growable buffers with manual memory management or temporary pools.
• Cross-Language Compatibility: Verified interoperability with Go using the official google.golang.org/protobuf package.
• Code Generator: Compile-time proto-to-C3 code generation via $exec.

Project Structure

• src/: Core implementation (buffer, wire, encoder, decoder, message).
• cmd/proto_gen.c3: Proto file parser and C3 code generator.
• test/: Unit test suite.
• example/: Cross-language example (C3 <-> Go). The Go implementation uses the official protowire package for ground-truth wire format validation.

Building & Testing

Build the library:

make build

Run tests:

make test

Run the example:

make -C example run

Build the proto generator:

c3c build proto_gen

Run the generator standalone:

bin/proto_gen path/to/file.proto  generated.c3

What Gets Generated

For each proto message:

• A C3 struct with proto-to-C3 type mapping
• encode(WriteBuffer* buf) method
• decode(char[] data) method

For each proto enum:

• A C3 constdef with integer values

For oneof fields:

• A tag constdef enum
• Pointer fields for each variant
• Tag field to track which variant is set

Proto → C3 Type Mapping

Proto Type	C3 Type
int32, sint32, sfixed32	int
int64, sint64, sfixed64	long
uint32, fixed32	uint
uint64, fixed64	ulong
float	float
double	double
bool	bool
string	String
bytes	char[]
repeated T	T[]
optional T	T*
Custom message	struct (inline)

Limitations

• repeated field decode currently emits comments for array append (C3 arrays are fixed-size)
• map types are not supported
• service definitions are skipped
• Nested messages within other messages are parsed but generate top-level structs

License

MIT