pub enum FieldsShape {
    Array {
        stride: Size,
        count: u64,
    Arbitrary {
        offsets: Vec<Size>,
        memory_index: Vec<u32>,
Expand description

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



Scalar primitives and !, which never have fields.


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



stride: Size
count: u64

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



offsets: Vec<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: Vec<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.

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.


Gets source indices of the fields by increasing offsets.

Trait Implementations

Formats the value using the given formatter. Read more

Feeds this value into the given Hasher. Read more

Feeds a slice of this type into the given Hasher. Read more

This method tests for self and other values to be equal, and is used by ==. Read more

This method tests for !=.

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

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

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.


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: 56 bytes

Size for each variant:

  • Primitive: 0 bytes
  • Union: 8 bytes
  • Array: 16 bytes
  • Arbitrary: 48 bytes