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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
/* global ChromeWorker */
let MESSAGE_COUNTER = 0;
function dumpn(_msg) {
// dump(msg + "\n");
}
/**
* Creates a wrapper around a ChromeWorker, providing easy
* communication to offload demanding tasks. The corresponding URL
* must implement the interface provided by `devtools/shared/worker/helper`.
*
* @param {string} url
* The URL of the worker.
* @param Object opts
* An option with the following optional fields:
* - name: a name that will be printed with logs
* - verbose: log incoming and outgoing messages
*/
export function DevToolsWorker(url, opts) {
opts = opts || {};
this._worker = new ChromeWorker(url);
this._verbose = opts.verbose;
this._name = opts.name;
this._worker.addEventListener("error", this.onError);
}
/**
* Performs the given task in a chrome worker, passing in data.
* Returns a promise that resolves when the task is completed, resulting in
* the return value of the task.
*
* @param {string} task
* The name of the task to execute in the worker.
* @param {any} data
* Data to be passed into the task implemented by the worker.
* @param {undefined|Array} transfer
* Optional array of transferable objects to transfer ownership of.
* @return {Promise}
*/
DevToolsWorker.prototype.performTask = function (task, data, transfer) {
if (this._destroyed) {
return Promise.reject(
"Cannot call performTask on a destroyed DevToolsWorker"
);
}
const worker = this._worker;
const id = ++MESSAGE_COUNTER;
const payload = { task, id, data };
if (this._verbose && dumpn) {
dumpn(
"Sending message to worker" +
(this._name ? " (" + this._name + ")" : "") +
": " +
JSON.stringify(payload, null, 2)
);
}
worker.postMessage(payload, transfer);
return new Promise((resolve, reject) => {
const listener = ({ data: result }) => {
if (this._verbose && dumpn) {
dumpn(
"Received message from worker" +
(this._name ? " (" + this._name + ")" : "") +
": " +
JSON.stringify(result, null, 2)
);
}
if (result.id !== id) {
return;
}
worker.removeEventListener("message", listener);
if (result.error) {
reject(result.error);
} else {
resolve(result.response);
}
};
worker.addEventListener("message", listener);
});
};
/**
* Terminates the underlying worker. Use when no longer needing the worker.
*/
DevToolsWorker.prototype.destroy = function () {
this._worker.terminate();
this._worker = null;
this._destroyed = true;
};
DevToolsWorker.prototype.onError = function ({ message, filename, lineno }) {
dump(new Error(message + " @ " + filename + ":" + lineno) + "\n");
};
/**
* Takes a function and returns a Worker-wrapped version of the same function.
* Returns a promise upon resolution.
* @see `./devtools/shared/shared/tests/browser/browser_devtools-worker-03.js
*
* ⚠ This should only be used for tests or A/B testing performance ⚠
*
* The original function must:
*
* Be a pure function, that is, not use any variables not declared within the
* function, or its arguments.
*
* Return a value or a promise.
*
* Note any state change in the worker will not affect the callee's context.
*
* @param {function} fn
* @return {function}
*/
export function workerify(fn) {
console.warn(
"`workerify` should only be used in tests or measuring performance. " +
"This creates an object URL on the browser window, and should not be " +
"used in production."
);
// Fetch modules here as we don't want to include it normally.
const { URL, Blob } = Services.wm.getMostRecentWindow("navigator:browser");
const stringifiedFn = createWorkerString(fn);
const blob = new Blob([stringifiedFn]);
const url = URL.createObjectURL(blob);
const worker = new DevToolsWorker(url);
const wrapperFn = (data, transfer) =>
worker.performTask("workerifiedTask", data, transfer);
wrapperFn.destroy = function () {
URL.revokeObjectURL(url);
worker.destroy();
};
return wrapperFn;
}
/**
* Takes a function, and stringifies it, attaching the worker-helper.js
* boilerplate hooks.
*/
function createWorkerString(fn) {
createTask(self, "workerifiedTask", ${fn.toString()});`;
}