Struct Page 

pub struct Page { /* private fields */ }

A 4KB page with header and content

This is the core data structure for the storage engine.

Implementations

impl Page

pub fn new(page_type: PageType, page_id: u32) -> Page

Create a new empty page

pub fn from_bytes(data: [u8; 4096]) -> Page

Create a page from raw bytes

pub fn from_slice(slice: &[u8]) -> Result<Page, PageError>

Create a page from a byte slice (must be exactly PAGE_SIZE)

pub fn as_bytes(&self) -> &[u8; 4096]

Get raw page data

pub fn as_bytes_mut(&mut self) -> &mut [u8; 4096]

Get mutable raw page data

pub fn header(&self) -> Result<PageHeader, PageError>

Get page header

pub fn set_header(&mut self, header: &PageHeader)

Set page header

pub fn page_type(&self) -> Result<PageType, PageError>

Get page type

pub fn page_id(&self) -> u32

Get page ID

pub fn lsn(&self) -> u64

Get the WAL Log Sequence Number stamped on this page.

0 means “no WAL guarantee” — the page was modified through a path that did not append a WAL record (freelist trunks, header shadow pages). The double-write buffer is responsible for the integrity of lsn == 0 pages.

See src/storage/engine/btree/README.md § Invariant 3.

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

Stamp the WAL LSN of the record describing the most recent mutation to this page. The pager’s flush path guarantees that the WAL is durable up to this LSN before writing the page to disk (WAL-first ordering — see PLAN.md § Target 3).

Callers should pass the LSN returned by WalWriter::append for the change record. Pass 0 only on legacy / non-WAL write paths (DWB-protected freelist + header writes).

pub fn cell_count(&self) -> u16

Get cell count

pub fn set_cell_count(&mut self, count: u16)

Set cell count

pub fn parent_id(&self) -> u32

Get parent page ID

pub fn set_parent_id(&mut self, parent_id: u32)

Set parent page ID

pub fn right_child(&self) -> u32

Get right child page ID (for interior nodes)

pub fn set_right_child(&mut self, child_id: u32)

Set right child page ID (for interior nodes)

pub fn free_start(&self) -> u16

Get free_start offset

pub fn set_free_start(&mut self, offset: u16)

Set free_start offset

pub fn free_end(&self) -> u16

Get free_end offset

pub fn set_free_end(&mut self, offset: u16)

Set free_end offset

pub fn content(&self) -> &[u8]

Get content area (everything after header)

pub fn content_mut(&mut self) -> &mut [u8]

Get mutable content area

pub fn update_checksum(&mut self)

Calculate and update checksum

pub fn verify_checksum(&self) -> Result<(), PageError>

Verify page checksum

pub fn get_cell_pointer(&self, index: usize) -> Result<u16, PageError>

Get cell pointer at index

Cell pointers are stored as u16 offsets starting at HEADER_SIZE.

pub fn set_cell_pointer( &mut self, index: usize, pointer: u16, ) -> Result<(), PageError>

Set cell pointer at index

pub fn get_cell(&self, index: usize) -> Result<&[u8], PageError>

Get cell data by index

pub fn insert_cell( &mut self, key: &[u8], value: &[u8], ) -> Result<usize, PageError>

Insert a new cell (key-value pair) into the page

Returns the cell index on success.

pub fn read_cell(&self, index: usize) -> Result<(Vec<u8>, Vec<u8>), PageError>

Read key and value from cell at index

pub fn search_key(&self, key: &[u8]) -> Result<usize, usize>

Binary search for key in sorted cell array

Returns Ok(index) if key is found, Err(insert_pos) if not.

pub fn new_header_page(page_count: u32) -> Page

Create a database header page (page 0)

pub fn read_page_count(&self) -> u32

Read page count from header page

pub fn write_page_count(&mut self, count: u32)

Write page count to header page

pub fn read_freelist_head(&self) -> u32

Read freelist head from header page

pub fn write_freelist_head(&mut self, page_id: u32)

Write freelist head to header page

pub fn verify_header_page(&self) -> Result<(), PageError>

Verify this is a valid header page

Trait Implementations

impl Clone for Page

fn clone(&self) -> Page

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Page

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

Formats the value using the given formatter.

impl Default for Page

fn default() -> Page

Returns the “default value” for a type.