s2-tools/dist/experimental/s2cell.js

A collection of geospatial tools primarily designed for WGS84, Web Mercator, and S2.

import wasmBase64 from './s2cell.wasm';
import { fromLonLat, toST } from '../geometry/s2/point';
/**
 * Generator that builds S2Cells from either lon/lat, S2Point, or face/s/t
 */
export class S2CellGenerator {
    instance;
    wasmMemory;
    tmpString = '';
    #finalizationRegistry;
    /**
     * Creates an instance of S2CellGenerator that manages the wasm memory
     */
    constructor() {
        const mod = new WebAssembly.Module(base64ToArrayBuffer(wasmBase64));
        this.instance = new WebAssembly.Instance(mod, {
            env: {},
        });
        this.#finalizationRegistry = new FinalizationRegistry((id) => {
            const freeS2CellId = this.instance.exports.free_s2_cell_id;
            freeS2CellId(id);
        });
    }
    /**
     * @param lon - longitude
     * @param lat - latitude
     * @returns - an S2Cell with the appropriate id and functions
     */
    fromLonLat(lon, lat) {
        return this.fromS2Point(fromLonLat(lon, lat));
    }
    /**
     * @param point - a vector point on the sphere
     * @returns - an S2Cell with the appropriate id and functions
     */
    fromS2Point(point) {
        const [face, s, t] = toST(point);
        return this.fromFaceST(face, s, t);
    }
    /**
     * @param face - face on the sphere
     * @param s - x position
     * @param t - y position
     * @returns - an S2Cell with the appropriate id and functions
     */
    fromFaceST(face, s, t) {
        const fromFaceST = this.instance.exports.from_face_st;
        const comparitor = this.instance.exports.compare_s2_cell_id;
        const id = fromFaceST(face, s, t);
        const cell = {
            id,
            /**
             * @param other - other S2Cell to compare to
             * @returns -1 | 0 | 1; -1 if this < other, 0 if this == other, 1 if this > other
             */
            compare: (other) => {
                return comparitor(id, other.id);
            },
        };
        // Register the id with the finalization registry to ensure it gets freed
        this.#finalizationRegistry.register(cell, id);
        return cell;
    }
}
/**
 * pollyfill for string to array buffer
 * @param base64 - base64 encoded string
 * @returns converted ArrayBuffer of the string data
 */
function base64ToArrayBuffer(base64) {
    const binaryString = atob(base64);
    const len = binaryString.length;
    const bytes = new Uint8Array(len);
    for (let i = 0; i < len; i++)
        bytes[i] = binaryString.charCodeAt(i);
    return bytes.buffer;
}
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