ProtoCache Rust

Rust implementation of ProtoCache, including the core runtime, mutable APIs, schema/reflection extensions, and a protoc code generator for typed Rust bindings.

[!WARNING]

This Rust workspace was generated with AI assistance. Treat it as generated software and verify behavior with tests and benchmarks before relying on it in production.

Release Status

The 0.1.x series is a beta-quality release. The wire-format compatibility, core read/write paths, reflection layer, and code generator are covered by the workspace compatibility suite, but the public Rust API may still change before 1.0. Processing hostile inputs has not yet received production-level fuzzing and Miri coverage.

Overview

The workspace is organized into four crates:

The portable schema subset is documented in the upstream schema reference, and the binary layout is documented in the upstream data-format reference.

Installation

Add the protobuf-free runtime:

cargo add protocache-core@0.1.0

Add schema, reflection, JSON, and Protobuf conversion support when needed:

cargo add protocache-extension@0.1.0

Install the protoc plugin:

cargo install protoc-gen-pcrs --version 0.1.0

Equivalent manifest dependencies are:

[dependencies]
protocache-core = "0.1.0"
# Optional, for reflection and Protobuf-facing workflows:
protocache-extension = "0.1.0"

The primary Rust-facing API layers are:

• protocache_core::runtime for zero-copy read access
• protocache_core::mutable for mutable message, map, and array APIs
• protocache_core::encoding for low-level buffer and encoding primitives
• protocache_extension::{reflection, utils} for schema-aware and protobuf-facing workflows

Benchmark

Using the local Rust harness in protocache-test on the bundled benchmark fixture with --loops 1000000. Timings are ns/op-equivalent local samples.

Mutable/serialize paths from the same Rust benchmark:

Build and Test

Run the full workspace test suite:

cargo test --workspace

Build the benchmark harness:

cargo build --release -p protocache-test

protocache-extension builds as a pure Rust crate by default. To enable direct .proto source parsing through the native libprotoc bridge:

cargo build -p protocache-extension --features native-proto

The native-proto feature currently supports Unix targets and requires a C++17 compiler (CXX may override c++), ar, and development installations of libprotoc and libprotobuf (on Ubuntu, install libprotoc-dev and libprotobuf-dev). The protocache-test harness enables this feature because its compatibility tests parse fixture schemas.

The Protobuf and ProtoCache benchmark binaries (test.pb and test.pc) are derived at build time from test.proto and test.json. The FlatBuffers binary is likewise derived from test.fbs and test-fb.json. These generated binaries are written to Cargo's OUT_DIR; they are not source fixtures.

Quick Start

Run the low-level encode and zero-copy read example:

cargo run -p protocache-core --example basic

Code Generation

Build the protoc plugin and generate typed readonly Rust APIs from the existing test schema:

cargo build -p protoc-gen-pcrs
mkdir -p generated
protoc \
  --proto_path=tests/fixtures/proto \
  --plugin=protoc-gen-pcrs=target/debug/protoc-gen-pcrs \
  --pcrs_out=generated \
  tests/fixtures/proto/test.proto

This writes generated/test.pc.rs. To also generate mutable APIs in generated/test.pc-ex.rs, pass the extra plugin parameter:

protoc \
  --proto_path=tests/fixtures/proto \
  --plugin=protoc-gen-pcrs=target/debug/protoc-gen-pcrs \
  --pcrs_out=extra:generated \
  tests/fixtures/proto/test.proto

Supported Platforms

The core runtime, extension, and code generator officially support 64-bit Rust targets. 32-bit targets are not tested and are outside the compatibility guarantee. The optional native-proto feature is additionally limited to Unix targets.

Dependency Boundary

The core runtime, code generator, and default protocache-extension build use Rust workspace crates and published Rust dependencies. Fixture reuse in tests and benchmarks is data reuse, not a runtime code dependency.

Native .proto parsing is an explicit exception: enabling protocache-extension/native-proto compiles src/proto_bridge.cc and dynamically links libprotoc, libprotobuf, and the platform C++ runtime. Additional developer workflows use external tools:

• protoc for code generation and descriptor-set workflows
• flatc and foryc for their optional local benchmark cases

Notes

For most integrations:

• start read-only access from protocache_core::runtime::MessageView
• use protocache_core::mutable for mutable document workflows
• add protocache-extension only when you need schema loading, reflection, or protobuf/prost conversion

Most users should not need to work with descriptor wiring or dynamic reflection types directly unless they are building schema-driven tooling.

Security and Compatibility

• The supported MSRV is Rust 1.89.
• Official support is limited to 64-bit targets.
• protocache-extension is pure Rust by default; native-proto adds a Unix-only C++/libprotoc FFI boundary.
• The repository test/benchmark crate is not published. Its pinned FlatBuffers and Fory dependencies are used only with checked-in, locally-generated benchmark fixtures and are not dependencies of the three public crates.
• Report suspected security issues privately to the maintainer using the contact address in the crate metadata.