Enum Chunk

enum Chunk {
    Zeros(u16),
    Ones(u16),
    Mixed(u16, u16, Rc<[u64; 32]>),
}

Variants

Zeros(u16)

A chunk that is all zeros; we don’t represent the zeros explicitly.

Ones(u16)

A chunk that is all ones; we don’t represent the ones explicitly.

Mixed(u16, u16, Rc<[u64; 32]>)

A chunk that has a mix of zeros and ones, which are represented explicitly and densely. It never has all zeros or all ones.

If this is the final chunk there may be excess, unused words. This turns out to be both simpler and have better performance than allocating the minimum number of words, largely because we avoid having to store the length, which would make this type larger. These excess words are always be zero, as are any excess bits in the final in-use word.

The second field is the count of 1s set in the chunk, and must satisfy 0 < count < chunk_domain_size.

The words are within an Rc because it’s surprisingly common to duplicate an entire chunk, e.g. in ChunkedBitSet::clone_from(), or when a Mixed chunk is union’d into a Zeros chunk. When we do need to modify a chunk we use Rc::make_mut.

Implementations

impl Chunk

fn new(chunk_domain_size: usize, is_empty: bool) -> Self

fn count(&self) -> usize

Count the number of 1s in the chunk.

Trait Implementations

impl Clone for Chunk

fn clone(&self) -> Chunk

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Chunk

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

Formats the value using the given formatter.

impl PartialEq for Chunk

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for Chunk

impl StructuralPartialEq for Chunk

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: 16 bytes

Size for each variant:

• Zeros: 2 bytes
• Ones: 2 bytes
• Mixed: 14 bytes