@loaders.gl/worker-utils/dist/lib/worker-utils/get-loadable-worker-url.js

Utilities for running tasks on worker threads

// loaders.gl
// SPDX-License-Identifier: MIT
// Copyright (c) vis.gl contributors
import { assert } from "../env-utils/assert.js";
const workerURLCache = new Map();
/**
 * Creates a loadable URL from worker source or URL
 * that can be used to create `Worker` instances.
 * Due to CORS issues it may be necessary to wrap a URL in a small importScripts
 * @param props
 * @param props.source Worker source
 * @param props.url Worker URL
 * @returns loadable url
 */
export function getLoadableWorkerURL(props) {
    assert((props.source && !props.url) || (!props.source && props.url)); // Either source or url must be defined
    let workerURL = workerURLCache.get(props.source || props.url);
    if (!workerURL) {
        // Differentiate worker urls from worker source code
        if (props.url) {
            workerURL = getLoadableWorkerURLFromURL(props.url);
            workerURLCache.set(props.url, workerURL);
        }
        if (props.source) {
            workerURL = getLoadableWorkerURLFromSource(props.source);
            workerURLCache.set(props.source, workerURL);
        }
    }
    assert(workerURL);
    return workerURL;
}
/**
 * Build a loadable worker URL from worker URL
 * @param url
 * @returns loadable URL
 */
function getLoadableWorkerURLFromURL(url) {
    // A local script url, we can use it to initialize a Worker directly
    if (!url.startsWith('http')) {
        return url;
    }
    // A remote script, we need to use `importScripts` to load from different origin
    const workerSource = buildScriptSource(url);
    return getLoadableWorkerURLFromSource(workerSource);
}
/**
 * Build a loadable worker URL from worker source
 * @param workerSource
 * @returns loadable url
 */
function getLoadableWorkerURLFromSource(workerSource) {
    const blob = new Blob([workerSource], { type: 'application/javascript' });
    return URL.createObjectURL(blob);
}
/**
 * Per spec, worker cannot be initialized with a script from a different origin
 * However a local worker script can still import scripts from other origins,
 * so we simply build a wrapper script.
 *
 * @param workerUrl
 * @returns source
 */
function buildScriptSource(workerUrl) {
    return `\
try {
  importScripts('${workerUrl}');
} catch (error) {
  console.error(error);
  throw error;
}`;
}