WorldWind Kotlin/earth.worldwind.layer.cache/FileSystemFeatureStore

FileSystemFeatureStore

class FileSystemFeatureStore(baseDirectory: String, contentKey: String, val cachePolicy: CachePolicy) : FeatureStore, CachedSourceInfoProvider

Filesystem-backed FeatureStore for iOS. One directory per content key under baseDirectory; layout:

${baseDirectory}/${contentKey}/features/bulk.json — entire bulk-row set, one JSON list.
${baseDirectory}/${contentKey}/features/tile_${z}_${x}_${y}.json — per-tile JSON list.

CachedGeometry is @Serializable already so rows go in / out as a single JSON encode / decode. The negative-cache sentinel (fetched-but-empty) writes a [] for the tile.

Constructors

FileSystemFeatureStore

constructor(baseDirectory: String, contentKey: String, cachePolicy: CachePolicy)

Properties

cacheInfo

open override val cacheInfo: CachedSourceInfo

cachePolicy

open override val cachePolicy: CachePolicy

Functions

deleteTile

open suspend override fun deleteTile(z: Int, x: Int, y: Int)

Drop a tile entry from the store.

evict

open suspend override fun evict()

Capacity eviction: drop whole per-tile files oldest-first (by mtime) until within CachePolicy.maxEntries (tile count). bulk.json (an atomic snapshot) is never touched. staleAfter never deletes.

readAll

open suspend override fun readAll(): Flow<CachedFeatureRow>

Read every bulk row ((z, x, y) IS NULL) in insertion order.

readBySector

open suspend fun readBySector(sector: Sector): Flow<CachedFeatureRow>

Read only the bulk rows whose geometry intersects sector. The default ignores sector and returns readAll — correct but unbounded; a spatially-indexed store (GeoPackage RTree) overrides it to serve viewport reads without loading the whole table.

readTile

open suspend override fun readTile(z: Int, x: Int, y: Int, sector: Sector? = null): Flow<CachedFeatureRow>?

Read rows for one tile, or null if the tile is absent (cache miss). An empty flow distinguishes "tile cached with zero rows" from "tile not cached". sector is the tile's true geographic bounds for the spatial query; null → derive Web-Mercator slippy bounds from (z, x, y) (back-compat for slippy-keyed tiles).

readTileLastModified

open suspend override fun readTileLastModified(z: Int, x: Int, y: Int): Long?

Epoch-millis the tile at (z, x, y) was last written, for stale-while-revalidate. Default null = freshness isn't tracked (the store opts out of SWR — its tiles are served but never background-refreshed).

replaceAll

open suspend override fun replaceAll(rows: Flow<CachedFeatureRow>)

Atomically replace every bulk row with the supplied flow. Existing tile-addressed rows are left untouched.

setBoundingSector

open suspend fun setBoundingSector(sector: Sector)

Persist sector as the store's content bounding box — the data-availability extent a bulk download records (e.g. gpkg_contents). Default no-op for stores without one.

sizeBytes

open suspend override fun sizeBytes(): Long

Approximate byte size of all rows in the store.

writeTile

open suspend override fun writeTile(z: Int, x: Int, y: Int, rows: Flow<CachedFeatureRow>, sector: Sector? = null)

Atomically replace rows for one tile. Pass an empty flow to record "tile has no features" — that's the negative cache for ocean / empty Overpass responses. sector is the tile's true geographic bounds (null → slippy bounds from (z, x, y)).