rkyv

rkyv (archive) is a zero-copy deserialization framework for Rust.

It's similar to other zero-copy deserialization frameworks such as Cap'n Proto and FlatBuffers. However, while the former have external schemas and heavily restricted data types, rkyv allows all serialized types to be defined in code and can serialize a wide variety of types that the others cannot. Additionally, rkyv is designed to have little to no overhead, and in most cases will perform exactly the same as native types.

rkyv has a hashmap implementation that is built for zero-copy deserialization, so you can serialize your hashmaps with abandon! The implementation is based off of the standard library's hashbrown crate and should have nearly identical performance.

One of the most impactful features made possible by rkyv is the ability to serialize trait objects and use them as trait objects without deserialization. See the archive_dyn crate for more details.

Design

Like serde, rkyv uses Rust's powerful trait system to serialize data without the need for reflection. Despite having a wide array of features, you also only pay for what you use. If your data checks out, the serialization process can be as simple as a memcpy! Like serde, this allows rkyv to perform at speeds similar to handwritten serializers.

Unlike serde, rkyv produces data that is guaranteed deserialization free. If you wrote your data to disk, you can just mmap your file into memory, cast a pointer, and your data is ready to use. This makes it ideal for high-performance and IO-limited applications.

Tradeoffs

rkyv is designed primarily for loading bulk game data as efficiently as possible. While rkyv is a great format for final data, it lacks a full schema system and isn't well equipped for data migration. Using a serialization library like serde can help fill these gaps, and you can use serde with the same types as rkyv conflict-free.

Features

• const_generics: Improves the implementations for some traits and provides an Archive implementation for slices with elements that implement ArchiveSelf. Ideal for #[no_std] environments.
• inline_more: Performs more aggressive function inlining.
• more_portable: Avoids using sse2-optimized intrinsics since they may cause alignment issues across machines. This feature may go away once any portability bugs are identified and fixed.
• nightly: Enables some nightly features, such as likely.
• specialization: Enables the unfinished specialization feature and provides more efficient implementations of some functions when working with ArchiveSelf types.
• std: Enables standard library support.

By default, the std and inline_more features are enabled.