Cesium-Prequel/Source/Workers/createTaskProcessorWorker.js

/* This file is automatically rebuilt by the Cesium build process. */
define(['./when-f31b6bd1'], function (when) { 'use strict';

  /**
   * Formats an error object into a String.  If available, uses name, message, and stack
   * properties, otherwise, falls back on toString().
   *
   * @function
   *
   * @param {*} object The item to find in the array.
   * @returns {String} A string containing the formatted error.
   */
  function formatError(object) {
    var result;

    var name = object.name;
    var message = object.message;
    if (when.defined(name) && when.defined(message)) {
      result = name + ": " + message;
    } else {
      result = object.toString();
    }

    var stack = object.stack;
    if (when.defined(stack)) {
      result += "\n" + stack;
    }

    return result;
  }

  // createXXXGeometry functions may return Geometry or a Promise that resolves to Geometry
  // if the function requires access to ApproximateTerrainHeights.
  // For fully synchronous functions, just wrapping the function call in a `when` Promise doesn't
  // handle errors correctly, hence try-catch
  function callAndWrap(workerFunction, parameters, transferableObjects) {
    var resultOrPromise;
    try {
      resultOrPromise = workerFunction(parameters, transferableObjects);
      return resultOrPromise; // errors handled by Promise
    } catch (e) {
      return when.when.reject(e);
    }
  }

  /**
   * Creates an adapter function to allow a calculation function to operate as a Web Worker,
   * paired with TaskProcessor, to receive tasks and return results.
   *
   * @function createTaskProcessorWorker
   *
   * @param {createTaskProcessorWorker.WorkerFunction} workerFunction The calculation function,
   *        which takes parameters and returns a result.
   * @returns {createTaskProcessorWorker.TaskProcessorWorkerFunction} A function that adapts the
   *          calculation function to work as a Web Worker onmessage listener with TaskProcessor.
   *
   *
   * @example
   * function doCalculation(parameters, transferableObjects) {
   *   // calculate some result using the inputs in parameters
   *   return result;
   * }
   *
   * return Cesium.createTaskProcessorWorker(doCalculation);
   * // the resulting function is compatible with TaskProcessor
   *
   * @see TaskProcessor
   * @see {@link http://www.w3.org/TR/workers/|Web Workers}
   * @see {@link http://www.w3.org/TR/html5/common-dom-interfaces.html#transferable-objects|Transferable objects}
   */
  function createTaskProcessorWorker(workerFunction) {
    var postMessage;

    return function (event) {
      var data = event.data;

      var transferableObjects = [];
      var responseMessage = {
        id: data.id,
        result: undefined,
        error: undefined,
      };

      return when.when(
        callAndWrap(workerFunction, data.parameters, transferableObjects)
      )
        .then(function (result) {
          responseMessage.result = result;
        })
        .otherwise(function (e) {
          if (e instanceof Error) {
            // Errors can't be posted in a message, copy the properties
            responseMessage.error = {
              name: e.name,
              message: e.message,
              stack: e.stack,
            };
          } else {
            responseMessage.error = e;
          }
        })
        .always(function () {
          if (!when.defined(postMessage)) {
            postMessage = when.defaultValue(self.webkitPostMessage, self.postMessage);
          }

          if (!data.canTransferArrayBuffer) {
            transferableObjects.length = 0;
          }

          try {
            postMessage(responseMessage, transferableObjects);
          } catch (e) {
            // something went wrong trying to post the message, post a simpler
            // error that we can be sure will be cloneable
            responseMessage.result = undefined;
            responseMessage.error =
              "postMessage failed with error: " +
              formatError(e) +
              "\n  with responseMessage: " +
              JSON.stringify(responseMessage);
            postMessage(responseMessage);
          }
        });
    };
  }

  return createTaskProcessorWorker;

});