Wrapper types

Wrapper types customize the way that fields of types are archived. In some cases, wrapper types merely change the default behavior to a preferred alternative. In other cases, wrapper types allow serializing types which do not have support for rkyv by default.

Annotating a field with #[rkyv(with = ..)] will wrap that field with the given types when the struct is serialized or deserialized. There's no performance penalty to wrapping types, but doing more or less work during serialization and deserialization can affect performance. This excerpt is from the documentation for ArchiveWith:

#[derive(Archive, Deserialize, Serialize)]
struct Example {
    #[rkyv(with = Incremented)]
    a: i32,
    // Another i32 field, but not incremented this time
    b: i32,
}

The Incremented wrapper is wrapping a, and the definition causes that field to be incremented in its archived form.