@loaders.gl/tiles/dist/tileset/tileset-cache.js

Common components for different tiles loaders.

// loaders.gl
// SPDX-License-Identifier: MIT
// Copyright (c) vis.gl contributors
import { DoublyLinkedList } from "../utils/doubly-linked-list.js";
/**
 * Stores tiles with content loaded.
 * @private
 */
export class TilesetCache {
    _list;
    _sentinel;
    _trimTiles;
    constructor() {
        // [head, sentinel) -> tiles that weren't selected this frame and may be removed from the cache
        // (sentinel, tail] -> tiles that were selected this frame
        this._list = new DoublyLinkedList();
        this._sentinel = this._list.add('sentinel');
        this._trimTiles = false;
    }
    reset() {
        // Move sentinel node to the tail so, at the start of the frame, all tiles
        // may be potentially replaced.  Tiles are moved to the right of the sentinel
        // when they are selected so they will not be replaced.
        this._list.splice(this._list.tail, this._sentinel);
    }
    touch(tile) {
        const node = tile._cacheNode;
        if (node) {
            this._list.splice(this._sentinel, node);
        }
    }
    add(tileset, tile, addCallback) {
        if (!tile._cacheNode) {
            tile._cacheNode = this._list.add(tile);
            if (addCallback) {
                addCallback(tileset, tile);
            }
        }
    }
    unloadTile(tileset, tile, unloadCallback) {
        const node = tile._cacheNode;
        if (!node) {
            return;
        }
        this._list.remove(node);
        tile._cacheNode = null;
        if (unloadCallback) {
            unloadCallback(tileset, tile);
        }
    }
    unloadTiles(tileset, unloadCallback) {
        const trimTiles = this._trimTiles;
        this._trimTiles = false;
        const list = this._list;
        const maximumMemoryUsageInBytes = tileset.maximumMemoryUsage * 1024 * 1024;
        // Traverse the list only to the sentinel since tiles/nodes to the
        // right of the sentinel were used this frame.
        // The sub-list to the left of the sentinel is ordered from LRU to MRU.
        const sentinel = this._sentinel;
        let node = list.head;
        while (node !== sentinel &&
            (tileset.gpuMemoryUsageInBytes > maximumMemoryUsageInBytes || trimTiles)) {
            // @ts-expect-error
            const tile = node.item;
            // @ts-expect-error
            node = node.next;
            this.unloadTile(tileset, tile, unloadCallback);
        }
    }
    trim() {
        this._trimTiles = true;
    }
}