Struct ChunkMut 

pub struct ChunkMut<'a, P: PackedField>(/* private fields */);

Guards one mutably borrowed chunk of a buffer.

The chunk size against the packing width decides which of two shapes the guard takes:

chunk >= one packed word  ->  a run of whole words, lent straight from the store
chunk <  one packed word  ->  the chunk's lanes copied into a word of their own

The first shape edits the store itself. Every edit is therefore already in place, and dropping the guard does nothing.

The second shape edits a copy taken when the guard is built. That copy holds the chunk’s lanes shifted down to start at lane 0. Dropping the guard writes them back to the lanes they came from, and nothing else.

WIDTH = 4, chunks of 2 elements, chunk 1 of word 0

word before   [ a b c d ]
detached      [ c d . . ]   lanes 2..4 copied down to lanes 0..2
after edits   [ y z . . ]
word on drop  [ a b y z ]   lanes 0..2 written back to lanes 2..4

So an edit to a sub-word chunk reaches the buffer when the guard drops, and not before. Neighbouring chunks sharing the word keep their elements, since the merge skips their lanes.

Only one such guard can exist at a time, since it borrows the buffer mutably. Two live guards over chunks of one word would each merge a stale copy. The later merge would then undo the earlier one.

Implementations

impl<'a, P: PackedField> ChunkMut<'a, P>

pub const fn chunk(&mut self) -> FieldSliceMut<'_, P>

Lends the chunk out as a mutable view, its first element at index 0.

A chunk of whole words is a view straight onto the store, so edits land at once. A narrower chunk is a view onto the detached copy, so edits land when this guard drops.

Trait Implementations

impl<'a, P: Debug + PackedField> Debug for ChunkMut<'a, P>

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

Formats the value using the given formatter.

impl<P: PackedField> Drop for ChunkMut<'_, P>

fn drop(&mut self)

Executes the destructor for this type.

fn pin_drop(self: Pin<&mut Self>)

🔬This is a nightly-only experimental API. (pin_ergonomics)

Execute the destructor for this type, but different to Drop::drop, it requires self to be pinned.