Trait object serialization for rkyv.

Resources

Learning Materials

• The rkyv book covers the motivation, architecture, and major features of rkyv
• The rkyv discord is a great place to get help with specific issues and meet other people using rkyv

Documentation

• rkyv, the core library
• rkyv_dyn, which adds trait object support to rkyv
• rkyv_typename, a type naming library

Benchmarks

• The rust serialization benchmark is a shootout style benchmark comparing many rust serialization solutions. It includes special benchmarks for zero-copy serialization solutions like rkyv.

Sister Crates

• bytecheck, which rkyv uses for validation
• ptr_meta, which rkyv uses for pointer manipulation
• rend, which rkyv uses for endian-agnostic features

Example

use rkyv::{
    archived_value,
    ser::{
        serializers::AllocSerializer,
        Serializer,
    },
    Archive,
    Archived,
    Deserialize,
    Infallible,
    Serialize,
};
use rkyv_dyn::archive_dyn;
use rkyv_typename::TypeName;

#[archive_dyn(deserialize)]
trait ExampleTrait {
    fn value(&self) -> String;
}

#[derive(Archive, Serialize, Deserialize)]
#[archive_attr(derive(TypeName))]
struct StringStruct(String);

#[archive_dyn(deserialize)]
impl ExampleTrait for StringStruct {
    fn value(&self) -> String {
        self.0.clone()
    }
}

impl ExampleTrait for Archived<StringStruct> {
    fn value(&self) -> String {
        self.0.as_str().to_string()
    }
}

#[derive(Archive, Serialize, Deserialize)]
#[archive_attr(derive(TypeName))]
struct IntStruct(i32);

#[archive_dyn(deserialize)]
impl ExampleTrait for IntStruct {
    fn value(&self) -> String {
        format!("{}", self.0)
    }
}

impl ExampleTrait for Archived<IntStruct> {
    fn value(&self) -> String {
        format!("{}", self.0)
    }
}

#[test]
fn main() {
    let boxed_int = Box::new(IntStruct(42)) as Box<dyn SerializeExampleTrait>;
    let boxed_string = Box::new(StringStruct("hello world".to_string())) as Box<dyn SerializeExampleTrait>;
    let mut serializer = AllocSerializer::<256>::default();

    let int_pos = serializer.serialize_value(&boxed_int).unwrap();
    let string_pos = serializer.serialize_value(&boxed_string).unwrap();
    let buf = serializer.into_serializer().into_inner();

    let archived_int = unsafe { archived_value::<Box<dyn SerializeExampleTrait>>(buf.as_ref(), int_pos) };
    let archived_string = unsafe { archived_value::<Box<dyn SerializeExampleTrait>>(buf.as_ref(), string_pos) };
    assert_eq!(archived_int.value(), "42");
    assert_eq!(archived_string.value(), "hello world");

    let deserialized_int: Box<dyn SerializeExampleTrait> = archived_int.deserialize(&mut Infallible).unwrap();
    let deserialized_string: Box<dyn SerializeExampleTrait> = archived_string.deserialize(&mut Infallible).unwrap();
    assert_eq!(deserialized_int.value(), "42");
    assert_eq!(deserialized_string.value(), "hello world");
}