Struct PrefetchBuffer 

pub struct PrefetchBuffer<S: AsyncRowSource> { /* private fields */ }

Wraps an AsyncRowSource and provides a synchronous RowSource view.

The buffer caches fetched rows in an LRU cache (capacity max_rows). On a cache miss it returns a placeholder row of Cell::Empty values and enqueues the row index for background prefetch. Callers are expected to drive the prefetch loop by calling flush_pending in an async context (e.g. a Tokio task or a wasm_bindgen_futures::spawn_local closure).

Placeholder row

A cache miss returns N Cell::Empty cells where N is column_defs().len(). Renderers may style such cells as loading placeholders (spinner, shimmer, etc.).

Thread safety

The inner state is wrapped in Arc<Mutex<_>> so PrefetchBuffer is Send + Sync and can be shared across threads or with async runtimes.

Implementations

impl<S: AsyncRowSource> PrefetchBuffer<S>

pub fn new(source: S, max_rows: usize, prefetch_ahead: usize) -> Self

Create a new buffer wrapping source.

• max_rows: maximum number of rows to hold in the LRU cache.
• prefetch_ahead: number of rows ahead of the viewport to enqueue for prefetch when request_prefetch is called.

pub fn request_prefetch(&self, start: usize, viewport_rows: usize)

Request that rows [start, start + viewport_rows + prefetch_ahead) be prefetched.

Non-cached rows are enqueued internally; call flush_pending in an async context to actually perform the fetches.

pub async fn flush_pending(&self) -> usize

Drive the prefetch loop, fetching all pending rows and storing them in the cache.

Should be called from an async context (e.g. a spawned task). Returns the number of rows successfully fetched in this call.

pub fn store_row(&self, index: usize, cells: Vec<Cell>)

Store a single already-fetched row directly into the cache.

Useful for callers that manage their own prefetch executor.

pub fn invalidate(&self)

Invalidate the entire cache (e.g. after a source mutation).

The next call to RowSource::row will trigger fresh prefetch requests for every accessed row.

pub fn cached_count(&self) -> usize

Number of rows currently held in the cache.

pub fn is_cached(&self, index: usize) -> bool

True if the given row index is in the cache.

pub fn source(&self) -> &S

Access the underlying async source.

Trait Implementations

impl<S: AsyncRowSource> Clone for PrefetchBuffer<S>

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<S: AsyncRowSource> RowSource for PrefetchBuffer<S>

fn row_count(&self) -> usize

Returns the total number of rows in the data source.

fn column_defs(&self) -> &[ColumnDef]

Returns the column definitions (name + preferred width).

fn row(&self, index: usize) -> Vec<Cell>

Returns the cells for row at the given index.

fn row_height(&self, index: usize) -> f32

Per-row height in logical pixels.

fn footer(&self) -> Option<Vec<Cell>>

Optional footer (aggregate) row displayed below the data rows.

fn set_cell( &mut self, _row: usize, _col: usize, _value: Cell, ) -> Result<(), TableError>

Attempt to set a cell value in the source.

fn children(&self, _row: usize) -> Option<Vec<usize>>

Optional children of a row, enabling tree / grouped tables.

fn indent_level(&self, _row: usize) -> usize

Indent level for a row in a tree / grouped table.