Struct MapNiche

pub struct MapNiche<W, N = DefaultNiche>
where
    W: ?Sized,
    N: ?Sized,
{ /* private fields */ }

Available on crate feature dep_rkyv only.

A wrapper that first applies another wrapper W to the value inside an Option and then niches the result based on the Niching N.

Example

use rkyv::{
    with::{AsBox, MapNiche},
    Archive, Serialize,
};

#[derive(Archive, Serialize)]
struct BasicExample {
    option: Option<HugeType>,
}

#[derive(Archive, Serialize)]
struct NichedExample {
    #[rkyv(with = MapNiche<AsBox>)]
    option: Option<HugeType>,
}

#[derive(Archive, Serialize)]
struct HugeType([u8; 1024]);

let basic_value = BasicExample { option: None };
let basic_bytes = rkyv::to_bytes(&basic_value)?;
assert_eq!(basic_bytes.len(), 1 + 1024);

let niched_value = NichedExample { option: None };
let niched_bytes = rkyv::to_bytes(&niched_value)?;
assert_eq!(niched_bytes.len(), 4); // size_of::<ArchivedBox<_>>()

Trait Implementations

impl<T, W, N> ArchiveWith<Option<T>> for MapNiche<W, N>

where W: ArchiveWith<T> + ?Sized, N: Niching<<W as ArchiveWith<T>>::Archived> + ?Sized,

type Archived = NichedOption<<W as ArchiveWith<T>>::Archived, N>

The archived type of Self with F.

type Resolver = Option<<W as ArchiveWith<T>>::Resolver>

The resolver of a Self with F.

fn resolve_with( field: &Option<T>, resolver: <MapNiche<W, N> as ArchiveWith<Option<T>>>::Resolver, out: Place<<MapNiche<W, N> as ArchiveWith<Option<T>>>::Archived>, )

Resolves the archived type using a reference to the field type F.

impl<W, N> Debug for MapNiche<W, N>

where W: ?Sized, N: ?Sized,

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<W, N> Default for MapNiche<W, N>

where W: ?Sized, N: ?Sized,

fn default() -> MapNiche<W, N>

Returns the “default value” for a type.

impl<T, W, N, D> DeserializeWith<NichedOption<<W as ArchiveWith<T>>::Archived, N>, Option<T>, D> for MapNiche<W, N>

where W: ArchiveWith<T> + DeserializeWith<<W as ArchiveWith<T>>::Archived, T, D>, N: Niching<<W as ArchiveWith<T>>::Archived> + ?Sized, D: Fallible + ?Sized,

fn deserialize_with( field: &NichedOption<<W as ArchiveWith<T>>::Archived, N>, deserializer: &mut D, ) -> Result<Option<T>, <D as Fallible>::Error>

Deserializes the field type F using the given deserializer.

impl<T, W, N, S> SerializeWith<Option<T>, S> for MapNiche<W, N>

where W: SerializeWith<T, S> + ?Sized, N: Niching<<W as ArchiveWith<T>>::Archived> + ?Sized, S: Fallible + ?Sized,

fn serialize_with( field: &Option<T>, serializer: &mut S, ) -> Result<<MapNiche<W, N> as ArchiveWith<Option<T>>>::Resolver, <S as Fallible>::Error>

Serializes the field type F using the given serializer.