WorldWind Kotlin/earth.worldwind.formats.archive/ReadOnlyArchive

ReadOnlyArchive

Read-only, open-in-place view over a local content archive — a path → bytes store, backed by whatever container the file actually is. Implementations today:

ZipFileArchive — a ZIP (ArcGIS SLPK, Cesium 3D Tiles Archive .3tz / 3TZ).
Sqlite3dTilesArchive — a SQLite package (Cesium .3dtiles, a media(key, content) table).

The point in every case is random access without reading or copying the whole file: resolve a logical entry path to its (decompressed) bytes on demand. Datasets are multi-GB, so RAM stays bounded by the index plus whatever is currently resident, NOT file size. The handle stays open for the layer's lifetime; close releases it.

readEntry returns the logical resource: if the stored entry is GZIP-compressed (I3S gzips its JSON + binary buffers; some .3dtiles producers gzip each blob), the implementation inflates it transparently. A plain ZIP .3tz and raw-stored .3dtiles blobs pass through unchanged.

Inheritors

Sqlite3dTilesArchive

ZipFileArchive

Properties

entryCount

abstract val entryCount: Int

Number of entries in the archive (diagnostic; also a proxy for index-memory pressure).

Functions

abstract fun close()

Release the underlying file handle. Idempotent.

hasEntry

abstract fun hasEntry(path: String): Boolean

True when path resolves to an entry. Cheap index/metadata lookup, no full read.

readEntry

abstract suspend fun readEntry(path: String): ByteArray?

Read and decompress the entry at path (archive-internal path, e.g. content/0/0.b3dm or nodes/1/geometries/0.bin). Returns null when the entry is absent. Runs the blocking read on an IO dispatcher in the implementation. Throws only on genuine IO failure, not on a miss.