Struct Field 

pub struct Field {
    pub name: Option<Symbol>,
    pub ty: TypeId,
    pub offset: u64,
    pub bit: u32,
    pub align: u64,
    pub bits: Option<u32>,
}

One member of a record, placed.

Fields

name: Option<Symbol>

The member name, absent for an unnamed bit-field or an anonymous member.

ty: TypeId

The member type.

offset: u64

Where the member starts, in bytes from the start of the record, rounded down.

For an ordinary member this is exactly where it starts. For a bit-field it is the byte the first of its bits lives in, which is a starting point for a load rather than an address the program may take.

Bytes and not bits, with Field::bit holding the rest. A record may be PTRDIFF_MAX bytes and that many bits is more than a u64 holds, so a single bit offset would make the largest record this compiler can lay out an eighth of the largest one C allows.

bit: u32

Which bit of that byte the member starts at, from zero to seven.

Always zero for an ordinary member, since every one of those starts on a byte boundary.

align: u64

What the member’s offset is a multiple of, which is the alignment it was placed at.

The same as the alignment of its type for most members, one byte under packed, and more than either where aligned asked for more. It is here because it is the only thing known about where a member sits once the offset stops being a number: an address is as aligned as the record is and as the offset into it is, and this is that second half.

bits: Option<u32>

The bit-field width, absent when the member is an ordinary one.

Implementations

impl Field

pub fn bit_offset(&self) -> u128

Where the member starts, in bits from the start of the record.

A u128 for the reason Field::offset is bytes. Nothing that generates code wants this number, which is why it is not what is stored: it is here because the layout rules were measured in bits and the tests that check them read in bits.

pub fn is_bit_field(&self) -> bool

Whether the member is a bit-field, zero width included.

Trait Implementations

impl Clone for Field

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Field

impl Debug for Field

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

Formats the value using the given formatter.

impl Eq for Field

impl PartialEq for Field

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Field