Prutal

Prutal is a pure Go alternative to protocol buffers, it covers most of the functionality offered by Protocol Buffers.

Prutal aims to minimize code generation as much as possible while ensuring serialization and maintaining good performance.

Since Prutal is NOT yet ready for production use, we are not providing usage documentation at this time, nor do we guarantee backward compatibility of the interface.

Feature Comparison

Protobuf Compatibility

• ✅ Works with code generated by the official Protocol Buffer Go (protoc-gen-go), open API and hybrid API without the protoopaque build tag
• ❌ Opaque API (default_api_level=API_OPAQUE, or the hybrid API built with -tags protoopaque): field presence lives in a bitmap the runtime does not maintain

Core Message Operations

• ✅ Marshal / Unmarshal — binary wire format
• ✅ MarshalAppend — append-friendly encoding
• ✅ Size — compute wire size without marshaling (zero allocation)
• ✅ Reset
• ❌ Clone / Merge / Equal
• ❌ CheckInitialized — validate required field presence
• ❌ MarshalOptions / UnmarshalOptions (deterministic output, discard unknown, recursion limits, etc.)

Proto Language Support

• ✅ Scalar types: all 15 protobuf scalar types
• ✅ Messages and nested messages
• ✅ Repeated fields
• ✅ Enums (including allow_alias)
• ✅ Optional / field presence
  • The presence of a bytes field is read from the struct tag as protoc-gen-go writes it: a field of a proto3 file carries proto3, a proto3 optional field oneof on top of it, and any other singular field has presence.
  • prutalgen writes the same markers, plus its own implicit marker for an edition 2023 field with features.field_presence = IMPLICIT, which protoc-gen-go leaves unmarked.
  • Code generated by earlier prutalgen versions carries no markers and is read as having presence: a bytes field without presence, proto3 or editions implicit, holding an empty non-nil slice is serialized as an empty field instead of being skipped. Decoders read it as the default value; regenerate to get the exact output.
  • protoc-gen-go output for an edition 2023 implicit bytes field has the same divergence, as the runtime cannot tell it from a field with presence.
• ✅ Map fields
• ✅ Oneof fields
• ✅ Required fields (proto2)
• ✅ Packed / unpacked encoding: written as declared, both forms are accepted on decode
  • PACKED / EXPANDED (repeated field encoding, edition 2023)
• ✅ Unknown field preservation
• ✅ Reserved fields and names
• ❌ Default scalar values (proto2, edition 2023)
• ❌ Groups (proto2, deprecated)
• ❌ UTF-8 validation
• ❌ Message sets (legacy format)

Encoding Formats

• ✅ Binary wire format
• ⚠️ JSON: struct tag only, no protojson equivalent
• ❌ Text format (prototext)
• ❌ Delimited format (length-prefixed message streams)

Reflection

• ❌ Descriptor-based reflection (protoreflect)
• ❌ Type registries (protoregistry)
• ❌ Dynamic messages (dynamicpb)

Extension Support

• ⚠️ Extensions (proto2): parsed but limited codegen
• ❌ Has / Get / Set / Clear / Range extensions
• ⚠️ Extensions set through protobuf-go are dropped by Marshal; on Unmarshal they are kept as unknown fields and written back as such

Code Generation (prutalgen)

• ✅ Proto2, proto3, edition 2023
• ✅ Imports (regular, public, weak)
• ✅ gRPC / Services (client/server stubs, streaming)
• ⚠️ Go only
• ⚠️ Well-known types: reuses google.golang.org/protobuf/types/known, Any is limited
• ⚠️ Custom options: subset of gogoproto options
• ❌ Edition 2024
• ❌ Opaque API / lazy decoding
• ❌ Deprecation markers

How to use Prutal with gRPC

Use pkg/grpccodec and pass grpccodec.PrutalCodec to the gRPC v1 codec APIs on both server and client.

See pkg/grpccodec/README.md for usage details and tests/cases/grpc for a complete example.

Contributing

Contributor guide: Contributing.

License

Prutal is licensed under the terms of the Apache license 2.0. See LICENSE for more information. Dependencies used by prutal are listed under licenses.