import defaultValue from "../Core/defaultValue.js";
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import defined from "../Core/defined.js";
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import formatError from "../Core/formatError.js";
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import when from "../ThirdParty/when.js";
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// createXXXGeometry functions may return Geometry or a Promise that resolves to Geometry
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// if the function requires access to ApproximateTerrainHeights.
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// For fully synchronous functions, just wrapping the function call in a `when` Promise doesn't
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// handle errors correctly, hence try-catch
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function callAndWrap(workerFunction, parameters, transferableObjects) {
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var resultOrPromise;
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try {
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resultOrPromise = workerFunction(parameters, transferableObjects);
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return resultOrPromise; // errors handled by Promise
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} catch (e) {
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return when.reject(e);
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}
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}
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/**
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* Creates an adapter function to allow a calculation function to operate as a Web Worker,
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* paired with TaskProcessor, to receive tasks and return results.
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*
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* @function createTaskProcessorWorker
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*
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* @param {createTaskProcessorWorker.WorkerFunction} workerFunction The calculation function,
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* which takes parameters and returns a result.
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* @returns {createTaskProcessorWorker.TaskProcessorWorkerFunction} A function that adapts the
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* calculation function to work as a Web Worker onmessage listener with TaskProcessor.
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*
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*
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* @example
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* function doCalculation(parameters, transferableObjects) {
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* // calculate some result using the inputs in parameters
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* return result;
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* }
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*
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* return Cesium.createTaskProcessorWorker(doCalculation);
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* // the resulting function is compatible with TaskProcessor
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*
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* @see TaskProcessor
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* @see {@link http://www.w3.org/TR/workers/|Web Workers}
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* @see {@link http://www.w3.org/TR/html5/common-dom-interfaces.html#transferable-objects|Transferable objects}
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*/
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function createTaskProcessorWorker(workerFunction) {
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var postMessage;
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return function (event) {
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var data = event.data;
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var transferableObjects = [];
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var responseMessage = {
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id: data.id,
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result: undefined,
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error: undefined,
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};
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return when(
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callAndWrap(workerFunction, data.parameters, transferableObjects)
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)
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.then(function (result) {
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responseMessage.result = result;
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})
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.otherwise(function (e) {
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if (e instanceof Error) {
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// Errors can't be posted in a message, copy the properties
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responseMessage.error = {
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name: e.name,
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message: e.message,
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stack: e.stack,
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};
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} else {
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responseMessage.error = e;
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}
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})
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.always(function () {
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if (!defined(postMessage)) {
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postMessage = defaultValue(self.webkitPostMessage, self.postMessage);
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}
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if (!data.canTransferArrayBuffer) {
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transferableObjects.length = 0;
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}
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try {
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postMessage(responseMessage, transferableObjects);
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} catch (e) {
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// something went wrong trying to post the message, post a simpler
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// error that we can be sure will be cloneable
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responseMessage.result = undefined;
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responseMessage.error =
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"postMessage failed with error: " +
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formatError(e) +
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"\n with responseMessage: " +
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JSON.stringify(responseMessage);
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postMessage(responseMessage);
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}
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});
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};
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}
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/**
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* A function that performs a calculation in a Web Worker.
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* @callback createTaskProcessorWorker.WorkerFunction
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*
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* @param {Object} parameters Parameters to the calculation.
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* @param {Array} transferableObjects An array that should be filled with references to objects inside
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* the result that should be transferred back to the main document instead of copied.
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* @returns {Object} The result of the calculation.
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*
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* @example
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* function calculate(parameters, transferableObjects) {
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* // perform whatever calculation is necessary.
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* var typedArray = new Float32Array(0);
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*
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* // typed arrays are transferable
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* transferableObjects.push(typedArray)
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*
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* return {
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* typedArray : typedArray
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* };
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* }
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*/
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/**
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* A Web Worker message event handler function that handles the interaction with TaskProcessor,
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* specifically, task ID management and posting a response message containing the result.
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* @callback createTaskProcessorWorker.TaskProcessorWorkerFunction
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*
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* @param {Object} event The onmessage event object.
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*/
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export default createTaskProcessorWorker;
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