# Enum rustc_abi::FieldsShape

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    pub enum FieldsShape<FieldIdx: Idx> {
        Primitive,
        Union(NonZeroUsize),
        Array {
            stride: Size,
            count: u64,
        },
        Arbitrary {
            offsets: IndexVec<FieldIdx, Size>,
            memory_index: IndexVec<FieldIdx, u32>,
        },
    }

Expand description

Describes how the fields of a type are located in memory.

## Variants§

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### Primitive

Scalar primitives and `!`, which never have fields.

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### Union(NonZeroUsize)

All fields start at no offset. The `usize` is the field count.

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### Array

Array/vector-like placement, with all fields of identical types.

#### Fields

§`stride: Size`
§`count: u64`
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### Arbitrary

Struct-like placement, with precomputed offsets.

Fields are guaranteed to not overlap, but note that gaps before, between and after all the fields are NOT always padding, and as such their contents may not be discarded. For example, enum variants leave a gap at the start, where the discriminant field in the enum layout goes.

#### Fields

§`offsets: IndexVec<FieldIdx, Size>`

Offsets for the first byte of each field, ordered to match the source definition order. This vector does not go in increasing order.

§`memory_index: IndexVec<FieldIdx, u32>`

Maps source order field indices to memory order indices, depending on how the fields were reordered (if at all). This is a permutation, with both the source order and the memory order using the same (0..n) index ranges.

Note that during computation of `memory_index`, sometimes it is easier to operate on the inverse mapping (that is, from memory order to source order), and that is usually named `inverse_memory_index`.

## Implementations§

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### impl<FieldIdx: Idx> FieldsShape<FieldIdx>

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#### pub fn count(&self) -> usize

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#### pub fn offset(&self, i: usize) -> Size

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#### pub fn memory_index(&self, i: usize) -> usize

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#### pub fn index_by_increasing_offset( &self, ) -> impl ExactSizeIterator<Item = usize> + '_

Gets source indices of the fields by increasing offsets.

## Trait Implementations§

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### impl<FieldIdx: Clone + Idx> Clone for FieldsShape<FieldIdx>

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#### fn clone(&self) -> FieldsShape<FieldIdx>

Returns a copy of the value. Read more
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#### fn clone_from(&mut self, source: &Self)

Performs copy-assignment from `source`. Read more
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### impl<FieldIdx: Debug + Idx> Debug for FieldsShape<FieldIdx>

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

Formats the value using the given formatter. Read more
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### impl<FieldIdx: Hash + Idx> Hash for FieldsShape<FieldIdx>

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#### fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given `Hasher`. Read more
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#### fn hash_slice<H>(data: &[Self], state: &mut H)
where H: Hasher, Self: Sized,

Feeds a slice of this type into the given `Hasher`. Read more
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### impl<FieldIdx, __CTX> HashStable<__CTX> for FieldsShape<FieldIdx>
where __CTX: HashStableContext, FieldIdx: HashStable<__CTX> + Idx,

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#### fn hash_stable(&self, __hcx: &mut __CTX, __hasher: &mut StableHasher)

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### impl<FieldIdx: PartialEq + Idx> PartialEq for FieldsShape<FieldIdx>

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#### fn eq(&self, other: &FieldsShape<FieldIdx>) -> bool

This method tests for `self` and `other` values to be equal, and is used by `==`.
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#### fn ne(&self, other: &Rhs) -> bool

This method tests for `!=`. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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### impl<FieldIdx: Eq + Idx> Eq for FieldsShape<FieldIdx>

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### impl<FieldIdx: Idx> StructuralPartialEq for FieldsShape<FieldIdx>

## Auto Trait Implementations§

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### impl<FieldIdx> DynSend for FieldsShape<FieldIdx>

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### impl<FieldIdx> DynSync for FieldsShape<FieldIdx>

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### impl<FieldIdx> Freeze for FieldsShape<FieldIdx>

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### impl<FieldIdx> RefUnwindSafe for FieldsShape<FieldIdx>

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### impl<FieldIdx> Send for FieldsShape<FieldIdx>

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### impl<FieldIdx> Sync for FieldsShape<FieldIdx>

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### impl<FieldIdx> Unpin for FieldsShape<FieldIdx>

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### impl<FieldIdx> UnwindSafe for FieldsShape<FieldIdx>

## Blanket Implementations§

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### impl<T> Aligned for T

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#### const ALIGN: Alignment = _

Alignment of `Self`.
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### impl<T> Any for T
where T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for T
where T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for T
where T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> CloneToUninit for T
where T: Clone,

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#### default unsafe fn clone_to_uninit(&self, dst: *mut T)

🔬This is a nightly-only experimental API. (`clone_to_uninit`)
Performs copy-assignment from `self` to `dst`. Read more
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### impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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#### fn equivalent(&self, key: &K) -> bool

Checks if this value is equivalent to the given key. Read more
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### impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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#### fn equivalent(&self, key: &K) -> bool

Checks if this value is equivalent to the given key. Read more
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### impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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#### fn equivalent(&self, key: &K) -> bool

Compare self to `key` and return `true` if they are equal.
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T> Instrument for T

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#### fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided `Span`, returning an `Instrumented` wrapper. Read more
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#### fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current `Span`, returning an `Instrumented` wrapper. Read more
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### impl<T, U> Into<U> for T
where U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T> IntoEither for T

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#### fn into_either(self, into_left: bool) -> Either<Self, Self>

Converts `self` into a `Left` variant of `Either<Self, Self>` if `into_left` is `true`. Converts `self` into a `Right` variant of `Either<Self, Self>` otherwise. Read more
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#### fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
where F: FnOnce(&Self) -> bool,

Converts `self` into a `Left` variant of `Either<Self, Self>` if `into_left(&self)` returns `true`. Converts `self` into a `Right` variant of `Either<Self, Self>` otherwise. Read more
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### impl<T> Pointable for T

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#### const ALIGN: usize = _

The alignment of pointer.
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#### type Init = T

The type for initializers.
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#### unsafe fn init(init: <T as Pointable>::Init) -> usize

Initializes a with the given initializer. Read more
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#### unsafe fn deref<'a>(ptr: usize) -> &'a T

Dereferences the given pointer. Read more
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#### unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

Mutably dereferences the given pointer. Read more
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#### unsafe fn drop(ptr: usize)

Drops the object pointed to by the given pointer. Read more
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### impl<T> ToOwned for T
where T: Clone,

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#### type Owned = T

The resulting type after obtaining ownership.
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#### fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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#### fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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### impl<T, U> TryFrom<U> for T
where U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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### impl<V, T> VZip<V> for T
where V: MultiLane<T>,

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#### fn vzip(self) -> V

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### impl<T> WithSubscriber for T

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#### fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
where S: Into<Dispatch>,

Attaches the provided `Subscriber` to this type, returning a `WithDispatch` wrapper. Read more
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#### fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default `Subscriber` to this type, returning a `WithDispatch` wrapper. Read more
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### impl<'a, T> Captures<'a> for T
where T: ?Sized,

## Layout§

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain `repr(...)` attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 48 bytes

Size for each variant:

- `Primitive`: 0 bytes
- `Union`: 8 bytes
- `Array`: 16 bytes
- `Arbitrary`: 48 bytes