Struct NicheInto 

pub struct NicheInto<N: ?Sized>(/* private fields */);

A wrapper that niches based on a generic Niching.

A common type combination is Option<Box<T>>. By niching None into the null pointer, the archived version can save some space on-disk.

Example

use core::mem::size_of;

use rkyv::{
    niche::niching::{NaN, Null},
    with::NicheInto,
    Archive, Archived,
};

#[derive(Archive)]
struct BasicExample {
    maybe_box: Option<Box<str>>,
    maybe_non_nan: Option<f32>,
}

#[derive(Archive)]
struct NichedExample {
    #[rkyv(with = NicheInto<Null>)]
    maybe_box: Option<Box<str>>,
    #[rkyv(with = NicheInto<NaN>)]
    maybe_non_nan: Option<f32>,
}

assert!(
    size_of::<Archived<BasicExample>>()
        > size_of::<Archived<NichedExample>>()
);

Trait Implementations

impl<T, N> ArchiveWith<Option<T>> for NicheInto<N>

where T: Archive, N: Niching<T::Archived> + ?Sized,

type Archived = NichedOption<<T as Archive>::Archived, N>

The archived type of Self with F.

type Resolver = Option<<T as Archive>::Resolver>

The resolver of a Self with F.

fn resolve_with( field: &Option<T>, resolver: Self::Resolver, out: Place<Self::Archived>, )

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

impl<N: ?Sized> Debug for NicheInto<N>

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

Formats the value using the given formatter.

impl<N: ?Sized> Default for NicheInto<N>

fn default() -> Self

Returns the “default value” for a type.

impl<T, N, D> DeserializeWith<NichedOption<<T as Archive>::Archived, N>, Option<T>, D> for NicheInto<N>

where T: Archive<Archived: Deserialize<T, D>>, N: Niching<T::Archived> + ?Sized, D: Fallible + ?Sized,

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

Deserializes the field type F using the given deserializer.

impl<T, N, S> SerializeWith<Option<T>, S> for NicheInto<N>

where T: Serialize<S>, N: Niching<T::Archived> + ?Sized, S: Fallible + ?Sized,

fn serialize_with( field: &Option<T>, serializer: &mut S, ) -> Result<Self::Resolver, S::Error>

Serializes the field type F using the given serializer.