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-rw-r--r--toolkit/components/promiseworker/PromiseWorker.sys.mjs447
-rw-r--r--toolkit/components/promiseworker/moz.build16
-rw-r--r--toolkit/components/promiseworker/tests/xpcshell/data/chrome.manifest1
-rw-r--r--toolkit/components/promiseworker/tests/xpcshell/data/worker.js40
-rw-r--r--toolkit/components/promiseworker/tests/xpcshell/test_Promise.js168
-rw-r--r--toolkit/components/promiseworker/tests/xpcshell/xpcshell.ini8
-rw-r--r--toolkit/components/promiseworker/worker/PromiseWorker.js239
-rw-r--r--toolkit/components/promiseworker/worker/moz.build9
8 files changed, 928 insertions, 0 deletions
diff --git a/toolkit/components/promiseworker/PromiseWorker.sys.mjs b/toolkit/components/promiseworker/PromiseWorker.sys.mjs
new file mode 100644
index 0000000000..b2c3d4804b
--- /dev/null
+++ b/toolkit/components/promiseworker/PromiseWorker.sys.mjs
@@ -0,0 +1,447 @@
+/* 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 file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * A wrapper around ChromeWorker with extended capabilities designed
+ * to simplify main thread-to-worker thread asynchronous function calls.
+ *
+ * This wrapper:
+ * - groups requests and responses as a method `post` that returns a `Promise`;
+ * - ensures that exceptions thrown on the worker thread are correctly deserialized;
+ * - provides some utilities for benchmarking various operations.
+ *
+ * Generally, you should use PromiseWorker.sys.mjs along with its worker-side
+ * counterpart PromiseWorker.js.
+ */
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+ PromiseUtils: "resource://gre/modules/PromiseUtils.sys.mjs",
+});
+
+/**
+ * An implementation of queues (FIFO).
+ *
+ * The current implementation uses one array, runs in O(n ^ 2), and is optimized
+ * for the case in which queues are generally short.
+ */
+function Queue() {
+ this._array = [];
+}
+Queue.prototype = {
+ pop: function pop() {
+ return this._array.shift();
+ },
+ push: function push(x) {
+ return this._array.push(x);
+ },
+ isEmpty: function isEmpty() {
+ return !this._array.length;
+ },
+};
+
+/**
+ * Constructors for decoding standard exceptions received from the
+ * worker.
+ */
+const EXCEPTION_CONSTRUCTORS = {
+ EvalError(error) {
+ let result = new EvalError(error.message, error.fileName, error.lineNumber);
+ result.stack = error.stack;
+ return result;
+ },
+ InternalError(error) {
+ let result = new InternalError(
+ error.message,
+ error.fileName,
+ error.lineNumber
+ );
+ result.stack = error.stack;
+ return result;
+ },
+ RangeError(error) {
+ let result = new RangeError(
+ error.message,
+ error.fileName,
+ error.lineNumber
+ );
+ result.stack = error.stack;
+ return result;
+ },
+ ReferenceError(error) {
+ let result = new ReferenceError(
+ error.message,
+ error.fileName,
+ error.lineNumber
+ );
+ result.stack = error.stack;
+ return result;
+ },
+ SyntaxError(error) {
+ let result = new SyntaxError(
+ error.message,
+ error.fileName,
+ error.lineNumber
+ );
+ result.stack = error.stack;
+ return result;
+ },
+ TypeError(error) {
+ let result = new TypeError(error.message, error.fileName, error.lineNumber);
+ result.stack = error.stack;
+ return result;
+ },
+ URIError(error) {
+ let result = new URIError(error.message, error.fileName, error.lineNumber);
+ result.stack = error.stack;
+ return result;
+ },
+ DOMException(error) {
+ let result = new DOMException(error.message, error.name);
+ return result;
+ },
+};
+
+/**
+ * An object responsible for dispatching messages to a chrome worker
+ * and routing the responses.
+ *
+ * Instances of this constructor who need logging may provide a method
+ * `log: function(...args) { ... }` in charge of printing out (or
+ * discarding) logs.
+ *
+ * Instances of this constructor may add exception handlers to
+ * `this.ExceptionHandlers`, if they need to handle custom exceptions.
+ *
+ * @param {string} url The url containing the source code for this worker,
+ * as in constructor ChromeWorker.
+ *
+ * @constructor
+ */
+export var BasePromiseWorker = function (url) {
+ if (typeof url != "string") {
+ throw new TypeError("Expecting a string");
+ }
+ this._url = url;
+
+ /**
+ * A set of methods, with the following
+ *
+ * ConstructorName: function({message, fileName, lineNumber}) {
+ * // Construct a new instance of ConstructorName based on
+ * // `message`, `fileName`, `lineNumber`
+ * }
+ *
+ * By default, this covers EvalError, InternalError, RangeError,
+ * ReferenceError, SyntaxError, TypeError, URIError.
+ */
+ this.ExceptionHandlers = Object.create(EXCEPTION_CONSTRUCTORS);
+
+ /**
+ * The queue of deferred, waiting for the completion of their
+ * respective job by the worker.
+ *
+ * Each item in the list may contain an additional field |closure|,
+ * used to store strong references to value that must not be
+ * garbage-collected before the reply has been received (e.g.
+ * arrays).
+ *
+ * @type {Queue<{deferred:deferred, closure:*=}>}
+ */
+ this._queue = new Queue();
+
+ /**
+ * The number of the current message.
+ *
+ * Used for debugging purposes.
+ */
+ this._id = 0;
+
+ /**
+ * The instant at which the worker was launched.
+ */
+ this.launchTimeStamp = null;
+
+ /**
+ * Timestamps provided by the worker for statistics purposes.
+ */
+ this.workerTimeStamps = null;
+};
+
+BasePromiseWorker.prototype = {
+ log() {
+ // By Default, ignore all logs.
+ },
+
+ /**
+ * Instantiate the worker lazily.
+ */
+ get _worker() {
+ if (this.__worker) {
+ return this.__worker;
+ }
+
+ let worker = (this.__worker = new ChromeWorker(this._url));
+
+ // We assume that we call to _worker for the purpose of calling
+ // postMessage().
+ this.launchTimeStamp = Date.now();
+
+ /**
+ * Receive errors that have been serialized by the built-in mechanism
+ * of DOM/Chrome Workers.
+ *
+ * PromiseWorker.js knows how to serialize a number of errors
+ * without losing information. These are treated by
+ * |worker.onmessage|. However, for other errors, we rely on
+ * DOM's mechanism for serializing errors, which transmits these
+ * errors through |worker.onerror|.
+ *
+ * @param {Error} error Some JS error.
+ */
+ worker.onerror = error => {
+ this.log(
+ "Received uncaught error from worker",
+ error.message,
+ error.filename,
+ error.lineno
+ );
+ error.preventDefault();
+ let { deferred } = this._queue.pop();
+ deferred.reject(error);
+ };
+
+ /**
+ * Receive messages from the worker, propagate them to the listeners.
+ *
+ * Messages must have one of the following shapes:
+ * - {ok: some_value} in case of success
+ * - {fail: some_error} in case of error, where
+ * some_error is an instance of |PromiseWorker.WorkerError|
+ *
+ * Messages may also contain a field |id| to help
+ * with debugging.
+ *
+ * Messages may also optionally contain a field |durationMs|, holding
+ * the duration of the function call in milliseconds.
+ *
+ * @param {*} msg The message received from the worker.
+ */
+ worker.onmessage = msg => {
+ this.log("Received message from worker", msg.data);
+ let handler = this._queue.pop();
+ let deferred = handler.deferred;
+ let data = msg.data;
+ if (data.id != handler.id) {
+ throw new Error(
+ "Internal error: expecting msg " +
+ handler.id +
+ ", " +
+ " got " +
+ data.id +
+ ": " +
+ JSON.stringify(msg.data)
+ );
+ }
+ if ("timeStamps" in data) {
+ this.workerTimeStamps = data.timeStamps;
+ }
+ if ("ok" in data) {
+ // Pass the data to the listeners.
+ deferred.resolve(data);
+ } else if ("fail" in data) {
+ // We have received an error that was serialized by the
+ // worker.
+ deferred.reject(new WorkerError(data.fail));
+ }
+ };
+ return worker;
+ },
+
+ /**
+ * Post a message to a worker.
+ *
+ * @param {string} fun The name of the function to call.
+ * @param {Array} args The arguments to pass to `fun`. If any
+ * of the arguments is a Promise, it is resolved before posting the
+ * message. If any of the arguments needs to be transfered instead
+ * of copied, this may be specified by making the argument an instance
+ * of `BasePromiseWorker.Meta` or by using the `transfers` argument.
+ * By convention, the last argument may be an object `options`
+ * with some of the following fields:
+ * - {number|null} outExecutionDuration A parameter to be filled with the
+ * duration of the off main thread execution for this call.
+ * @param {*=} closure An object holding references that should not be
+ * garbage-collected before the message treatment is complete.
+ * @param {Array=} transfers An array of objects that should be transfered
+ * to the worker instead of being copied. If any of the objects is a Promise,
+ * it is resolved before posting the message.
+ *
+ * @return {promise}
+ */
+ post(fun, args, closure, transfers) {
+ return async function postMessage() {
+ // Normalize in case any of the arguments is a promise
+ if (args) {
+ args = await Promise.resolve(Promise.all(args));
+ }
+ if (transfers) {
+ transfers = await Promise.resolve(Promise.all(transfers));
+ } else {
+ transfers = [];
+ }
+
+ if (args) {
+ // Extract `Meta` data
+ args = args.map(arg => {
+ if (arg instanceof BasePromiseWorker.Meta) {
+ if (arg.meta && "transfers" in arg.meta) {
+ transfers.push(...arg.meta.transfers);
+ }
+ return arg.data;
+ }
+ return arg;
+ });
+ }
+
+ let id = ++this._id;
+ let message = { fun, args, id };
+ this.log("Posting message", message);
+ try {
+ this._worker.postMessage(message, ...[transfers]);
+ } catch (ex) {
+ if (typeof ex == "number") {
+ this.log("Could not post message", message, "due to xpcom error", ex);
+ // handle raw xpcom errors (see eg bug 961317)
+ throw new Components.Exception("Error in postMessage", ex);
+ }
+
+ this.log("Could not post message", message, "due to error", ex);
+ throw ex;
+ }
+
+ let deferred = lazy.PromiseUtils.defer();
+ this._queue.push({ deferred, closure, id });
+ this.log("Message posted");
+
+ let reply;
+ try {
+ this.log("Expecting reply");
+ reply = await deferred.promise;
+ } catch (error) {
+ this.log("Got error", error);
+ reply = error;
+
+ if (error instanceof WorkerError) {
+ // We know how to deserialize most well-known errors
+ throw this.ExceptionHandlers[error.data.exn](error.data);
+ }
+
+ if (ErrorEvent.isInstance(error)) {
+ // Other errors get propagated as instances of ErrorEvent
+ this.log(
+ "Error serialized by DOM",
+ error.message,
+ error.filename,
+ error.lineno
+ );
+ throw new Error(error.message, error.filename, error.lineno);
+ }
+
+ // We don't know about this kind of error
+ throw error;
+ }
+
+ // By convention, the last argument may be an object `options`.
+ let options = null;
+ if (args) {
+ options = args[args.length - 1];
+ }
+
+ // Check for duration and return result.
+ if (
+ !options ||
+ typeof options !== "object" ||
+ !("outExecutionDuration" in options)
+ ) {
+ return reply.ok;
+ }
+ // If reply.durationMs is not present, just return the result,
+ // without updating durations (there was an error in the method
+ // dispatch).
+ if (!("durationMs" in reply)) {
+ return reply.ok;
+ }
+ // Bug 874425 demonstrates that two successive calls to Date.now()
+ // can actually produce an interval with negative duration.
+ // We assume that this is due to an operation that is so short
+ // that Date.now() is not monotonic, so we round this up to 0.
+ let durationMs = Math.max(0, reply.durationMs);
+ // Accumulate (or initialize) outExecutionDuration
+ if (typeof options.outExecutionDuration == "number") {
+ options.outExecutionDuration += durationMs;
+ } else {
+ options.outExecutionDuration = durationMs;
+ }
+ return reply.ok;
+ }.bind(this)();
+ },
+
+ /**
+ * Terminate the worker, if it has been created at all, and set things up to
+ * be instantiated lazily again on the next `post()`.
+ * If there are pending Promises in the queue, we'll reject them and clear it.
+ */
+ terminate() {
+ if (!this.__worker) {
+ return;
+ }
+
+ try {
+ this.__worker.terminate();
+ delete this.__worker;
+ } catch (ex) {
+ // Ignore exceptions, only log them.
+ this.log("Error whilst terminating ChromeWorker: " + ex.message);
+ }
+
+ let error;
+ while (!this._queue.isEmpty()) {
+ if (!error) {
+ // We create this lazily, because error objects are not cheap.
+ error = new Error("Internal error: worker terminated");
+ }
+ let { deferred } = this._queue.pop();
+ deferred.reject(error);
+ }
+ },
+};
+
+/**
+ * An error that has been serialized by the worker.
+ *
+ * @constructor
+ */
+function WorkerError(data) {
+ this.data = data;
+}
+
+/**
+ * A constructor used to send data to the worker thread while
+ * with special treatment (e.g. transmitting data instead of
+ * copying it).
+ *
+ * @param {object=} data The data to send to the caller thread.
+ * @param {object=} meta Additional instructions, as an object
+ * that may contain the following fields:
+ * - {Array} transfers An array of objects that should be transferred
+ * instead of being copied.
+ *
+ * @constructor
+ */
+BasePromiseWorker.Meta = function (data, meta) {
+ this.data = data;
+ this.meta = meta;
+};
diff --git a/toolkit/components/promiseworker/moz.build b/toolkit/components/promiseworker/moz.build
new file mode 100644
index 0000000000..b6a2bb96e9
--- /dev/null
+++ b/toolkit/components/promiseworker/moz.build
@@ -0,0 +1,16 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# 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
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIRS += ["worker"]
+
+EXTRA_JS_MODULES += [
+ "PromiseWorker.sys.mjs",
+]
+
+XPCSHELL_TESTS_MANIFESTS += ["tests/xpcshell/xpcshell.ini"]
+
+with Files("**"):
+ BUG_COMPONENT = ("Toolkit", "Async Tooling")
diff --git a/toolkit/components/promiseworker/tests/xpcshell/data/chrome.manifest b/toolkit/components/promiseworker/tests/xpcshell/data/chrome.manifest
new file mode 100644
index 0000000000..9e5dd29b22
--- /dev/null
+++ b/toolkit/components/promiseworker/tests/xpcshell/data/chrome.manifest
@@ -0,0 +1 @@
+content promiseworker ./
diff --git a/toolkit/components/promiseworker/tests/xpcshell/data/worker.js b/toolkit/components/promiseworker/tests/xpcshell/data/worker.js
new file mode 100644
index 0000000000..ffb3473713
--- /dev/null
+++ b/toolkit/components/promiseworker/tests/xpcshell/data/worker.js
@@ -0,0 +1,40 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/* eslint-env mozilla/chrome-worker */
+
+"use strict";
+
+// Trivial worker definition
+
+/* import-globals-from /toolkit/components/workerloader/require.js */
+importScripts("resource://gre/modules/workers/require.js");
+var PromiseWorker = require("resource://gre/modules/workers/PromiseWorker.js");
+
+var worker = new PromiseWorker.AbstractWorker();
+worker.dispatch = function (method, args = []) {
+ return Agent[method](...args);
+};
+worker.postMessage = function (...args) {
+ self.postMessage(...args);
+};
+worker.close = function () {
+ self.close();
+};
+worker.log = function (...args) {
+ dump("Worker: " + args.join(" ") + "\n");
+};
+self.addEventListener("message", msg => worker.handleMessage(msg));
+self.addEventListener("unhandledrejection", function (error) {
+ throw error.reason;
+});
+
+var Agent = {
+ bounce(...args) {
+ return args;
+ },
+
+ throwError(msg, ...args) {
+ throw new Error(msg);
+ },
+};
diff --git a/toolkit/components/promiseworker/tests/xpcshell/test_Promise.js b/toolkit/components/promiseworker/tests/xpcshell/test_Promise.js
new file mode 100644
index 0000000000..f7581b664f
--- /dev/null
+++ b/toolkit/components/promiseworker/tests/xpcshell/test_Promise.js
@@ -0,0 +1,168 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+/* eslint-disable mozilla/no-arbitrary-setTimeout */
+
+"use strict";
+
+const { BasePromiseWorker } = ChromeUtils.importESModule(
+ "resource://gre/modules/PromiseWorker.sys.mjs"
+);
+const { setTimeout } = ChromeUtils.importESModule(
+ "resource://gre/modules/Timer.sys.mjs"
+);
+
+// Worker must be loaded from a chrome:// uri, not a file://
+// uri, so we first need to load it.
+
+var WORKER_SOURCE_URI = "chrome://promiseworker/content/worker.js";
+do_load_manifest("data/chrome.manifest");
+var worker = new BasePromiseWorker(WORKER_SOURCE_URI);
+worker.log = function (...args) {
+ info("Controller: " + args.join(" "));
+};
+
+// Test that simple messages work
+add_task(async function test_simple_args() {
+ let message = ["test_simple_args", Math.random()];
+ let result = await worker.post("bounce", message);
+ Assert.equal(JSON.stringify(result), JSON.stringify(message));
+});
+
+// Test that it works when we don't provide a message
+add_task(async function test_no_args() {
+ let result = await worker.post("bounce");
+ Assert.equal(JSON.stringify(result), JSON.stringify([]));
+});
+
+// Test that messages with promise work
+add_task(async function test_promise_args() {
+ let message = ["test_promise_args", Promise.resolve(Math.random())];
+ let stringified = JSON.stringify(await Promise.resolve(Promise.all(message)));
+ let result = await worker.post("bounce", message);
+ Assert.equal(JSON.stringify(result), stringified);
+});
+
+// Test that messages with delayed promise work
+add_task(async function test_delayed_promise_args() {
+ let promise = new Promise(resolve =>
+ setTimeout(() => resolve(Math.random()), 10)
+ );
+ let message = ["test_delayed_promise_args", promise];
+ let stringified = JSON.stringify(await Promise.resolve(Promise.all(message)));
+ let result = await worker.post("bounce", message);
+ Assert.equal(JSON.stringify(result), stringified);
+});
+
+// Test that messages with rejected promise cause appropriate errors
+add_task(async function test_rejected_promise_args() {
+ let error = new Error();
+ let message = ["test_promise_args", Promise.reject(error)];
+ try {
+ await worker.post("bounce", message);
+ do_throw("I shound have thrown an error by now");
+ } catch (ex) {
+ if (ex != error) {
+ throw ex;
+ }
+ info("I threw the right error");
+ }
+});
+
+// Test that we can transfer to the worker using argument `transfer`
+add_task(async function test_transfer_args() {
+ let array = new Uint8Array(4);
+ for (let i = 0; i < 4; ++i) {
+ array[i] = i;
+ }
+ Assert.equal(array.buffer.byteLength, 4, "The buffer is not detached yet");
+
+ let result = (
+ await worker.post("bounce", [array.buffer], [], [array.buffer])
+ )[0];
+
+ // Check that the buffer has been sent
+ Assert.equal(array.buffer.byteLength, 0, "The buffer has been detached");
+
+ // Check that the result is correct
+ Assert.equal(result.byteLength, 4, "The result has the right size");
+ let array2 = new Uint8Array(result);
+ for (let i = 0; i < 4; ++i) {
+ Assert.equal(array2[i], i);
+ }
+});
+
+// Test that we can transfer to the worker using an instance of `Meta`
+add_task(async function test_transfer_with_meta() {
+ let array = new Uint8Array(4);
+ for (let i = 0; i < 4; ++i) {
+ array[i] = i;
+ }
+ Assert.equal(array.buffer.byteLength, 4, "The buffer is not detached yet");
+
+ let message = new BasePromiseWorker.Meta(array, {
+ transfers: [array.buffer],
+ });
+ let result = (await worker.post("bounce", [message]))[0];
+
+ // Check that the buffer has been sent
+ Assert.equal(array.buffer.byteLength, 0, "The buffer has been detached");
+
+ // Check that the result is correct
+ Assert.equal(
+ Object.prototype.toString.call(result),
+ "[object Uint8Array]",
+ "The result appears to be a Typed Array"
+ );
+ Assert.equal(result.byteLength, 4, "The result has the right size");
+
+ for (let i = 0; i < 4; ++i) {
+ Assert.equal(result[i], i);
+ }
+});
+
+add_task(async function test_throw_error() {
+ try {
+ await worker.post("throwError", ["error message"]);
+ Assert.ok(false, "should have thrown");
+ } catch (ex) {
+ Assert.equal(ex.message, "Error: error message");
+ }
+});
+
+add_task(async function test_terminate() {
+ let previousWorker = worker._worker;
+
+ // Send two messages that we'll expect to be rejected.
+ let message = ["test_simple_args", Math.random()];
+ let promise1 = worker.post("bounce", message);
+ let promise2 = worker.post("throwError", ["error message"]);
+ // Skip a few beats so we can be sure that the two messages are in the queue.
+ await Promise.resolve();
+ await Promise.resolve();
+
+ worker.terminate();
+
+ await Assert.rejects(
+ promise1,
+ /worker terminated/,
+ "Pending promise should be rejected"
+ );
+ await Assert.rejects(
+ promise2,
+ /worker terminated/,
+ "Pending promise should be rejected"
+ );
+
+ // Unfortunately, there's no real way to check whether a terminate worked from
+ // the JS API. We'll just have to assume it worked.
+
+ // Post and test a simple message to ensure that the worker has been re-instantiated.
+ message = ["test_simple_args", Math.random()];
+ let result = await worker.post("bounce", message);
+ Assert.equal(JSON.stringify(result), JSON.stringify(message));
+ Assert.notEqual(
+ worker._worker,
+ previousWorker,
+ "ChromeWorker instances should differ"
+ );
+});
diff --git a/toolkit/components/promiseworker/tests/xpcshell/xpcshell.ini b/toolkit/components/promiseworker/tests/xpcshell/xpcshell.ini
new file mode 100644
index 0000000000..4922f3f091
--- /dev/null
+++ b/toolkit/components/promiseworker/tests/xpcshell/xpcshell.ini
@@ -0,0 +1,8 @@
+[DEFAULT]
+head=
+skip-if = toolkit == 'android'
+support-files=
+ data/worker.js
+ data/chrome.manifest
+
+[test_Promise.js]
diff --git a/toolkit/components/promiseworker/worker/PromiseWorker.js b/toolkit/components/promiseworker/worker/PromiseWorker.js
new file mode 100644
index 0000000000..b87e6c7e51
--- /dev/null
+++ b/toolkit/components/promiseworker/worker/PromiseWorker.js
@@ -0,0 +1,239 @@
+/* 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 file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* eslint-env commonjs, mozilla/chrome-worker */
+
+/**
+ * A wrapper around `self` with extended capabilities designed
+ * to simplify main thread-to-worker thread asynchronous function calls.
+ *
+ * This wrapper:
+ * - groups requests and responses as a method `post` that returns a `Promise`;
+ * - ensures that exceptions thrown on the worker thread are correctly serialized;
+ * - provides some utilities for benchmarking various operations.
+ *
+ * Generally, you should use PromiseWorker.js along with its main thread-side
+ * counterpart PromiseWorker.jsm.
+ */
+
+"use strict";
+
+if (typeof Components != "undefined") {
+ throw new Error("This module is meant to be used from the worker thread");
+}
+if (typeof require == "undefined" || typeof module == "undefined") {
+ throw new Error(
+ "this module is meant to be imported using the implementation of require() at resource://gre/modules/workers/require.js"
+ );
+}
+
+/* import-globals-from /toolkit/components/workerloader/require.js */
+importScripts("resource://gre/modules/workers/require.js");
+
+/**
+ * Built-in JavaScript exceptions that may be serialized without
+ * loss of information.
+ */
+const EXCEPTION_NAMES = {
+ EvalError: "EvalError",
+ InternalError: "InternalError",
+ RangeError: "RangeError",
+ ReferenceError: "ReferenceError",
+ SyntaxError: "SyntaxError",
+ TypeError: "TypeError",
+ URIError: "URIError",
+};
+
+/**
+ * A constructor used to return data to the caller thread while
+ * also executing some specific treatment (e.g. shutting down
+ * the current thread, transmitting data instead of copying it).
+ *
+ * @param {object=} data The data to return to the caller thread.
+ * @param {object=} meta Additional instructions, as an object
+ * that may contain the following fields:
+ * - {bool} shutdown If |true|, shut down the current thread after
+ * having sent the result.
+ * - {Array} transfers An array of objects that should be transferred
+ * instead of being copied.
+ *
+ * @constructor
+ */
+function Meta(data, meta) {
+ this.data = data;
+ this.meta = meta;
+}
+exports.Meta = Meta;
+
+/**
+ * Base class for a worker.
+ *
+ * Derived classes are expected to provide the following methods:
+ * {
+ * dispatch: function(method, args) {
+ * // Dispatch a call to method `method` with args `args`
+ * },
+ * log: function(...msg) {
+ * // Log (or discard) messages (optional)
+ * },
+ * postMessage: function(message, ...transfers) {
+ * // Post a message to the main thread
+ * },
+ * close: function() {
+ * // Close the worker
+ * }
+ * }
+ *
+ * By default, the AbstractWorker is not connected to a message port,
+ * hence will not receive anything.
+ *
+ * To connect it, use `onmessage`, as follows:
+ * self.addEventListener("message", msg => myWorkerInstance.handleMessage(msg));
+ * To handle rejected promises we receive from handleMessage, we must connect it to
+ * the onError handler as follows:
+ * self.addEventListener("unhandledrejection", function(error) {
+ * throw error.reason;
+ * });
+ */
+function AbstractWorker(agent) {
+ this._agent = agent;
+}
+AbstractWorker.prototype = {
+ // Default logger: discard all messages
+ log() {},
+
+ /**
+ * Handle a message.
+ */
+ async handleMessage(msg) {
+ let data = msg.data;
+ this.log("Received message", data);
+ let id = data.id;
+
+ let start;
+ let options;
+ if (data.args) {
+ options = data.args[data.args.length - 1];
+ }
+ // If |outExecutionDuration| option was supplied, start measuring the
+ // duration of the operation.
+ if (
+ options &&
+ typeof options === "object" &&
+ "outExecutionDuration" in options
+ ) {
+ start = Date.now();
+ }
+
+ let result;
+ let exn;
+ let durationMs;
+ let method = data.fun;
+ try {
+ this.log("Calling method", method);
+ result = await this.dispatch(method, data.args);
+ this.log("Method", method, "succeeded");
+ } catch (ex) {
+ exn = ex;
+ this.log(
+ "Error while calling agent method",
+ method,
+ exn,
+ exn.moduleStack || exn.stack || ""
+ );
+ }
+
+ if (start) {
+ // Record duration
+ durationMs = Date.now() - start;
+ this.log("Method took", durationMs, "ms");
+ }
+
+ // Now, post a reply, possibly as an uncaught error.
+ // We post this message from outside the |try ... catch| block
+ // to avoid capturing errors that take place during |postMessage| and
+ // built-in serialization.
+ if (!exn) {
+ this.log("Sending positive reply", result, "id is", id);
+ if (result instanceof Meta) {
+ if ("transfers" in result.meta) {
+ // Take advantage of zero-copy transfers
+ this.postMessage(
+ { ok: result.data, id, durationMs },
+ result.meta.transfers
+ );
+ } else {
+ this.postMessage({ ok: result.data, id, durationMs });
+ }
+ if (result.meta.shutdown || false) {
+ // Time to close the worker
+ this.close();
+ }
+ } else {
+ this.postMessage({ ok: result, id, durationMs });
+ }
+ } else if (exn.constructor.name == "DOMException") {
+ // We can receive instances of DOMExceptions with file I/O.
+ // DOMExceptions are not yet serializable (Bug 1561357) and must be
+ // handled differently, as they only have a name and message
+ this.log("Sending back DOM exception", exn.constructor.name);
+ let error = {
+ exn: exn.constructor.name,
+ message: exn.message,
+ };
+ this.postMessage({ fail: error, id, durationMs });
+ } else if (exn.constructor.name in EXCEPTION_NAMES) {
+ // Rather than letting the DOM mechanism [de]serialize built-in
+ // JS errors, which loses lots of information (in particular,
+ // the constructor name, the moduleName and the moduleStack),
+ // we [de]serialize them manually with a little more care.
+ this.log("Sending back exception", exn.constructor.name, "id is", id);
+ let error = {
+ exn: exn.constructor.name,
+ message: exn.message,
+ fileName: exn.moduleName || exn.fileName,
+ lineNumber: exn.lineNumber,
+ stack: exn.moduleStack,
+ };
+ this.postMessage({ fail: error, id, durationMs });
+ } else if ("toMsg" in exn) {
+ // Extension mechanism for exception [de]serialization. We
+ // assume that any exception with a method `toMsg()` knows how
+ // to serialize itself. The other side is expected to have
+ // registered a deserializer using the `ExceptionHandlers`
+ // object.
+ this.log(
+ "Sending back an error that knows how to serialize itself",
+ exn,
+ "id is",
+ id
+ );
+ let msg = exn.toMsg();
+ this.postMessage({ fail: msg, id, durationMs });
+ } else {
+ // If we encounter an exception for which we have no
+ // serialization mechanism in place, we have no choice but to
+ // let the DOM handle said [de]serialization. We can just
+ // attempt to mitigate the data loss by injecting `moduleName` and
+ // `moduleStack`.
+ this.log(
+ "Sending back regular error",
+ exn,
+ exn.moduleStack || exn.stack,
+ "id is",
+ id
+ );
+
+ try {
+ // Attempt to introduce human-readable filename and stack
+ exn.filename = exn.moduleName;
+ exn.stack = exn.moduleStack;
+ } catch (_) {
+ // Nothing we can do
+ }
+ throw exn;
+ }
+ },
+};
+exports.AbstractWorker = AbstractWorker;
diff --git a/toolkit/components/promiseworker/worker/moz.build b/toolkit/components/promiseworker/worker/moz.build
new file mode 100644
index 0000000000..6851eb80b4
--- /dev/null
+++ b/toolkit/components/promiseworker/worker/moz.build
@@ -0,0 +1,9 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# 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
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+EXTRA_JS_MODULES.workers = [
+ "PromiseWorker.js",
+]