Struct PageMut 

pub struct PageMut<'a> { /* private fields */ }

Implementations

impl<'a> PageMut<'a>

pub fn init(b: &'a mut [u8], kind: PageKind, tree_id: u16, page_no: u32) -> Self

pub fn reopen(b: &'a mut [u8]) -> Self

Reopen an already-initialised buffer for modification.

pub fn nentries_pub(&self) -> usize

Number of entries currently in a page under construction. Public because btree.rs’s splits, and pack_tree in a later task, need to know where the next insert_slot call will land while building a fresh page from a collected Vec of records.

pub fn free_space(&self) -> usize

pub fn set_next_leaf(&mut self, p: u32)

pub fn set_child0(&mut self, p: u32)

Same field, named for its meaning on an interior page.

pub fn insert_slot(&mut self, at: usize, rec: &[u8]) -> Result<()>

Insert rec so that it becomes entry at, shifting later slots right.

pub fn remove_slot(&mut self, at: usize)

Remove entry at. The payload bytes are abandoned in place; they are reclaimed only when the page is compacted.

SACRIFICE (Law 4): a page can hold dead payload bytes it cannot reuse until compaction. Bought: deletion touches only the slot directory.

pub fn compact(&mut self)

Rewrite every live payload packed against the end of the page, in slot order, and reset free_ptr to reclaim whatever remove_slot left abandoned. This is the reclamation remove_slot’s doc comment promises; without it that comment was a cheque the code could not cash, and a caller that relied on it (a replace on an already-tight leaf) would corrupt the page instead.

Bounded by one page: the snapshot below is at most PAGE_SIZE bytes, so this is RAM proportional to the page, not the store (Law 1).

pub fn finalise(&mut self, lsn: u64)

Close out a mutation: stamp the LSN. The checksum is stamped by seal immediately before a page is WRITTEN – a page mutated fifty times before eviction needs one checksum, not fifty (measured: 12.34 full-page CRCs per row, 10 of them re-verifying resident pages, 34% of the write path). A dirty resident page’s checksum field is meaningless; nothing reads it, and the only path to disk seals first.