@loaders.gl/worker-utils/dist/lib/worker-utils/get-transfer-list.js

Utilities for running tasks on worker threads

// loaders.gl
// SPDX-License-Identifier: MIT
// Copyright (c) vis.gl contributors
// NOTE - there is a copy of this function is both in core and loader-utils
// core does not need all the utils in loader-utils, just this one.
/**
 * Returns an array of Transferrable objects that can be used with postMessage
 * https://developer.mozilla.org/en-US/docs/Web/API/Worker/postMessage
 * @param object data to be sent via postMessage
 * @param recursive - not for application use
 * @param transfers - not for application use
 * @returns a transfer list that can be passed to postMessage
 */
export function getTransferList(object, recursive = true, transfers) {
    // Make sure that items in the transfer list is unique
    const transfersSet = transfers || new Set();
    if (!object) {
        // ignore
    }
    else if (isTransferable(object)) {
        transfersSet.add(object);
    }
    else if (isTransferable(object.buffer)) {
        // Typed array
        transfersSet.add(object.buffer);
    }
    else if (ArrayBuffer.isView(object)) {
        // object is a TypeArray viewing into a SharedArrayBuffer (not transferable)
        // Do not iterate through the content in this case
    }
    else if (recursive && typeof object === 'object') {
        for (const key in object) {
            // Avoid perf hit - only go one level deep
            getTransferList(object[key], recursive, transfersSet);
        }
    }
    // If transfers is defined, is internal recursive call
    // Otherwise it's called by the user
    return transfers === undefined ? Array.from(transfersSet) : [];
}
// https://developer.mozilla.org/en-US/docs/Web/API/Transferable
function isTransferable(object) {
    if (!object) {
        return false;
    }
    if (object instanceof ArrayBuffer) {
        return true;
    }
    if (typeof MessagePort !== 'undefined' && object instanceof MessagePort) {
        return true;
    }
    if (typeof ImageBitmap !== 'undefined' && object instanceof ImageBitmap) {
        return true;
    }
    // @ts-ignore
    if (typeof OffscreenCanvas !== 'undefined' && object instanceof OffscreenCanvas) {
        return true;
    }
    return false;
}
/**
 * Recursively drop non serializable values like functions and regexps.
 * @param object
 */
export function getTransferListForWriter(object) {
    if (object === null) {
        return {};
    }
    const clone = Object.assign({}, object);
    Object.keys(clone).forEach((key) => {
        // Typed Arrays and Arrays are passed with no change
        if (typeof object[key] === 'object' &&
            !ArrayBuffer.isView(object[key]) &&
            !(object[key] instanceof Array)) {
            clone[key] = getTransferListForWriter(object[key]);
        }
        else if (typeof clone[key] === 'function' || clone[key] instanceof RegExp) {
            clone[key] = {};
        }
        else {
            clone[key] = object[key];
        }
    });
    return clone;
}
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