rmp-serde

rmp-serde connects Rust’s low-level rmp MessagePack codec to Serde, so any type deriving Serialize/Deserialize can be encoded to and decoded from the compact binary MessagePack format with to_vec()/from_slice() calls and no manual byte-level encoding. It’s the standard way Rust projects adopt MessagePack as a faster, smaller alternative to JSON for wire formats, caches, and file formats, without writing custom binary parsers.

What You Get

• to_vec()/from_slice() and streaming Serializer/Deserializer types for MessagePack encoding/decoding
• Automatic support for any type implementing Serde’s Serialize/Deserialize traits, including derived structs and enums
• Configurable serialization modes (struct-as-map vs struct-as-array) via the config module for interop with other MessagePack consumers
• A bytes module for efficient handling of raw byte slices without unnecessary copies
• Interop with the sibling rmpv crate’s dynamic Value type for schema-less MessagePack handling

Common Use Cases

• Serializing Rust structs to a compact binary wire format for RPC or network protocols instead of JSON
• Persisting application state or cache entries to disk in MessagePack for smaller file sizes and faster (de)serialization
• Interoperating with services in other languages that already speak MessagePack (Python, JavaScript, Go clients)
• Replacing JSON in performance-sensitive paths where payload size and (de)serialization speed matter

Under The Hood

Architecture - rmp-serde is one of four crates in the msgpack-rust Cargo workspace (rmp, rmp-serde, rmpv, rmpv-tests): rmp implements the raw MessagePack wire format, and rmp-serde builds Serde’s Serializer/Deserializer trait implementations directly on top of it, translating Serde’s visitor-based data model into MessagePack’s type markers without an intermediate representation. Tech Stack - Pure Rust (edition 2024, Rust 1.85+), depending only on serde and the sibling rmp crate by path within the workspace, with rmpv and serde_bytes used only as dev-dependencies for testing byte-slice and dynamic-value interop. Code Quality - Source is organized by concern (encode.rs, decode.rs, config.rs, bytes.rs, each several hundred lines), with a dedicated tests/ directory and benches/ for serialization performance, though the crate’s own Cargo.toml carries a maintenance = "looking-for-maintainer" badge, signaling reduced active maintenance despite continued heavy real-world usage. API Design - The API deliberately mirrors serde_json’s (to_vec, from_slice, to_writer), so developers already familiar with Serde-based JSON handling can switch to MessagePack with minimal code changes, while the config module exposes struct-encoding-mode toggles for cases where wire-format compatibility with non-Rust MessagePack consumers matters.