onnx-rs

Zero-dependency ONNX model parser and encoder in Rust. Parses .onnx files (protobuf wire format) directly into typed Rust structs without relying on prost, protobuf, or any other crate.

Usage

use onnx_rs::ast::*;

// Parse
let bytes = std::fs::read("model.onnx").unwrap();
let model = onnx_rs::parse(&bytes).unwrap();

let graph = model.graph.as_ref().unwrap();
for node in &graph.node {
    match &node.op_type {
        OpType::Conv => println!("found conv: {}", node.name),
        OpType::Relu => println!("found relu: {}", node.name),
        op => println!("{}: {}", op, node.name),
    }
}

// Encode back to protobuf
let bytes = onnx_rs::encode(&model);
std::fs::write("output.onnx", &bytes).unwrap();

Features

• Zero dependencies — hand-rolled protobuf wire format decoder
• Typed AST — OpType enum with 170+ standard ONNX operators, Custom(String) fallback for vendor ops
• Full ONNX IR — Model, Graph, Node, TensorProto, TypeProto (Tensor/Sequence/Map/Optional/SparseTensor), Attribute, Function, TrainingInfo
• All 23 data types — including Float8 (e4m3fn, e5m2, etc.), Int4, Uint4, BFloat16
• Roundtrip encode/decode — parse() and encode() are fully symmetric