Protowire C#

PXF (Proto eXpressive Format) is a human-friendly text serialization format backed by protobuf schemas.

This is the C# (.NET 10.0+) port of the original Go Protowire library. It provides:

• PXF: A human-friendly text representation of Protobuf messages.
• Protowire.Pb: Reflection-based binary Protobuf marshaling for native C# classes.
• Protowire.Sbe: FIX SBE (Simple Binary Encoding) for ultra-low-latency use cases.

@type infra.v1.ServerConfig

hostname = "web-01.prod.example.com"
port     = 8443
enabled  = true
status   = STATUS_SERVING

# Well-known type literals
created_at = 2024-01-15T10:30:00Z
timeout    = 30s

# Nested messages use block syntax
tls {
  cert_file = "/etc/ssl/cert.pem"
  key_file  = "/etc/ssl/key.pem"
  verify    = true
}

# Repeated fields use list syntax
tags = ["production", "us-east", "frontend"]

# Maps use : for key-value pairs
labels = {
  env: "production"
  team: "platform"
  "hello world": "quoted keys supported"
}

Why PXF?

Format	Problem
JSON	Loosely typed, no comments, verbose, ambiguous without schema
YAML	Indentation-fragile, type coercion surprises (no -> false), complex spec
Protobuf textproto	No list/map literals, repeated fields are ugly, : separators feel archaic

PXF uses your existing .proto files as the schema. No new schema language. No ambiguity — the parser always knows every field's type.

Struct binary marshaling (Protowire.Pb)

Marshal any C# class to/from protobuf binary using [Protowire(N)] attributes — no .proto files or code generation required for simple use cases.

using Protowire.Pb;

public class Endpoint {
    [Protowire(1)] public string Path { get; set; } = "";
    [Protowire(2)] public string Method { get; set; } = "";
    [Protowire(3)] public int Port { get; set; }
}

public class Config {
    [Protowire(1)] public string Hostname { get; set; } = "";
    [Protowire(2)] public bool Enabled { get; set; }
    [Protowire(3)] public List<Endpoint> Endpoints { get; set; } = new();
    [Protowire(4)] public byte[] Data { get; set; }
}

// Encode
var data = Pb.Marshal(new Config {
    Hostname = "web-01",
    Enabled = true,
    Endpoints = { new Endpoint { Path = "/api", Method = "GET", Port = 8080 } }
});

// Decode
var cfg = new Config();
Pb.Unmarshal(data, cfg);

The output is standard protobuf binary — wire-compatible with any .proto definition using the same field numbers.

Supported types

• bool, int, long, uint, ulong, float, double
• string, byte[]
• BigInteger, Decimal, BigFloat (Protowire extensions)
• Enums
• Nested classes
• List<T>, Arrays, Dictionary<K, V>

PXF C# API (Protowire.Pxf)

Unmarshal

var decoder = new Protowire.Pxf.Decoder();
var config = new ServerConfig();
decoder.Unmarshal(pxfText, config);

The decoder automatically maps PXF keys to C# property names. It handles both ExactMatch and snake_case to PascalCase mapping (e.g., transport_error -> TransportError).

Marshal

var encoder = new Protowire.Pxf.Encoder();
string pxfText = encoder.Marshal(config);

Code Generation (buf.build)

This project uses buf.build for managing .proto files and generating C# code.

To generate C# code from the schemas in the proto/ directory:

buf generate proto

Generated files are placed in the Generated/ folders of each project (e.g., src/Protowire.Envelope/Generated/).

Project Structure

• src/Protowire.Pb: Core reflection-based Protobuf binary codec.
• src/Protowire.Pxf: PXF text format Lexer, Parser, and AST.
• src/Protowire.Envelopes: Standard API response envelope port.
• src/Protowire.Sbe: FIX SBE implementation.
• proto/: Shared Protobuf schemas.
• tests/: XUnit test suites for each component.
• cmd/{Protowire.BenchPxf, Protowire.BenchSbe, Protowire.DumpEnvelope}: Cross-port test harnesses.

Limitations & open gaps

Built on Google.Protobuf reflection (MessageDescriptor, IFieldAccessor) — the descriptor-driven design means the same codec works for any compiled-in message type. A few items fall out of that or are deferred:

• net10.0 minimum. The build leans on C# 13 features (collection expressions, file-scoped types). Targeting net8.0 or earlier would require backporting and is not currently planned.
• Google.Protobuf doesn't expose extension fields as readable named fields on FieldOptions for arbitrary .proto files. The (pxf.required) / (pxf.default) reader works because the AnnotationsExtensions class is shipped in this repo; downstream .proto files that bring their own extensions need their generated *Extensions class on the runtime classpath.
• No async API on the codec surface. All decode / encode is synchronous in-memory. For very large PXF documents an async streaming surface would be welcome.
• The CLI lives in trendvidia/protowire/cmd/protowire, not here. This repo ships only the library + cross-port harnesses.

Contributing & governance

This repository is part of the protowire-* family and is governed by Steward — the meritocratic, AI-driven governance engine that runs all of the ports. Voting weight is per-directory expertise, the constitution is public in governance.pxf, and Steward routes draft / first-time PRs through a private mentorship pipeline so initial contributions get private feedback rather than public-review friction.

If any of the items above sound interesting, pull requests are welcome. New contributors start at zero trust and accumulate influence by shipping merged PRs in the directories they actually work on — the escrow pipeline auto-routes large first-time PRs through 2–3 sandbox issues before unlocking them for community review.

See the Steward README for a longer walkthrough of vector reputation, escrow, and the immune system.