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410 lines
11 KiB
JavaScript
410 lines
11 KiB
JavaScript
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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"use strict";
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/* General utilities used throughout devtools. */
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var { Ci, Cu } = require("chrome");
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var Services = require("Services");
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var promise = require("promise");
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var { setTimeout } = require("Timer");
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/**
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* Turn the error |aError| into a string, without fail.
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*/
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exports.safeErrorString = function safeErrorString(aError) {
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try {
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let errorString = aError.toString();
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if (typeof errorString == "string") {
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// Attempt to attach a stack to |errorString|. If it throws an error, or
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// isn't a string, don't use it.
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try {
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if (aError.stack) {
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let stack = aError.stack.toString();
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if (typeof stack == "string") {
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errorString += "\nStack: " + stack;
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}
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}
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} catch (ee) { }
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// Append additional line and column number information to the output,
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// since it might not be part of the stringified error.
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if (typeof aError.lineNumber == "number" && typeof aError.columnNumber == "number") {
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errorString += "Line: " + aError.lineNumber + ", column: " + aError.columnNumber;
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}
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return errorString;
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}
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} catch (ee) { }
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return "<failed trying to find error description>";
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}
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/**
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* Report that |aWho| threw an exception, |aException|.
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*/
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exports.reportException = function reportException(aWho, aException) {
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let msg = aWho + " threw an exception: " + exports.safeErrorString(aException);
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dump(msg + "\n");
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if (Cu.reportError) {
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/*
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* Note that the xpcshell test harness registers an observer for
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* console messages, so when we're running tests, this will cause
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* the test to quit.
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*/
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Cu.reportError(msg);
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}
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}
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/**
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* Given a handler function that may throw, return an infallible handler
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* function that calls the fallible handler, and logs any exceptions it
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* throws.
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*
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* @param aHandler function
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* A handler function, which may throw.
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* @param aName string
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* A name for aHandler, for use in error messages. If omitted, we use
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* aHandler.name.
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*
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* (SpiderMonkey does generate good names for anonymous functions, but we
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* don't have a way to get at them from JavaScript at the moment.)
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*/
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exports.makeInfallible = function makeInfallible(aHandler, aName) {
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if (!aName)
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aName = aHandler.name;
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return function (/* arguments */) {
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try {
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return aHandler.apply(this, arguments);
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} catch (ex) {
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let who = "Handler function";
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if (aName) {
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who += " " + aName;
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}
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exports.reportException(who, ex);
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}
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}
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}
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/**
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* Interleaves two arrays element by element, returning the combined array, like
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* a zip. In the case of arrays with different sizes, undefined values will be
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* interleaved at the end along with the extra values of the larger array.
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*
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* @param Array a
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* @param Array b
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* @returns Array
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* The combined array, in the form [a1, b1, a2, b2, ...]
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*/
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exports.zip = function zip(a, b) {
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if (!b) {
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return a;
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}
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if (!a) {
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return b;
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}
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const pairs = [];
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for (let i = 0, aLength = a.length, bLength = b.length;
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i < aLength || i < bLength;
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i++) {
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pairs.push([a[i], b[i]]);
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}
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return pairs;
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};
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/**
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* Waits for the next tick in the event loop to execute a callback.
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*/
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exports.executeSoon = function executeSoon(aFn) {
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if (isWorker) {
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setTimeout(aFn, 0);
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} else {
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Services.tm.mainThread.dispatch({
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run: exports.makeInfallible(aFn)
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}, Ci.nsIThread.DISPATCH_NORMAL);
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}
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};
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/**
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* Waits for the next tick in the event loop.
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*
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* @return Promise
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* A promise that is resolved after the next tick in the event loop.
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*/
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exports.waitForTick = function waitForTick() {
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let deferred = promise.defer();
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exports.executeSoon(deferred.resolve);
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return deferred.promise;
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};
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/**
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* Waits for the specified amount of time to pass.
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*
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* @param number aDelay
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* The amount of time to wait, in milliseconds.
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* @return Promise
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* A promise that is resolved after the specified amount of time passes.
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*/
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exports.waitForTime = function waitForTime(aDelay) {
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let deferred = promise.defer();
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setTimeout(deferred.resolve, aDelay);
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return deferred.promise;
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};
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/**
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* Like Array.prototype.forEach, but doesn't cause jankiness when iterating over
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* very large arrays by yielding to the browser and continuing execution on the
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* next tick.
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*
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* @param Array aArray
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* The array being iterated over.
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* @param Function aFn
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* The function called on each item in the array. If a promise is
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* returned by this function, iterating over the array will be paused
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* until the respective promise is resolved.
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* @returns Promise
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* A promise that is resolved once the whole array has been iterated
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* over, and all promises returned by the aFn callback are resolved.
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*/
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exports.yieldingEach = function yieldingEach(aArray, aFn) {
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const deferred = promise.defer();
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let i = 0;
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let len = aArray.length;
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let outstanding = [deferred.promise];
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(function loop() {
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const start = Date.now();
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while (i < len) {
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// Don't block the main thread for longer than 16 ms at a time. To
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// maintain 60fps, you have to render every frame in at least 16ms; we
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// aren't including time spent in non-JS here, but this is Good
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// Enough(tm).
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if (Date.now() - start > 16) {
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exports.executeSoon(loop);
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return;
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}
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try {
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outstanding.push(aFn(aArray[i], i++));
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} catch (e) {
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deferred.reject(e);
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return;
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}
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}
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deferred.resolve();
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}());
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return promise.all(outstanding);
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}
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/**
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* Like XPCOMUtils.defineLazyGetter, but with a |this| sensitive getter that
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* allows the lazy getter to be defined on a prototype and work correctly with
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* instances.
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*
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* @param Object aObject
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* The prototype object to define the lazy getter on.
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* @param String aKey
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* The key to define the lazy getter on.
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* @param Function aCallback
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* The callback that will be called to determine the value. Will be
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* called with the |this| value of the current instance.
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*/
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exports.defineLazyPrototypeGetter =
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function defineLazyPrototypeGetter(aObject, aKey, aCallback) {
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Object.defineProperty(aObject, aKey, {
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configurable: true,
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get: function() {
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const value = aCallback.call(this);
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Object.defineProperty(this, aKey, {
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configurable: true,
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writable: true,
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value: value
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});
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return value;
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}
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});
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}
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/**
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* Safely get the property value from a Debugger.Object for a given key. Walks
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* the prototype chain until the property is found.
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*
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* @param Debugger.Object aObject
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* The Debugger.Object to get the value from.
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* @param String aKey
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* The key to look for.
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* @return Any
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*/
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exports.getProperty = function getProperty(aObj, aKey) {
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let root = aObj;
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try {
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do {
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const desc = aObj.getOwnPropertyDescriptor(aKey);
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if (desc) {
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if ("value" in desc) {
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return desc.value;
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}
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// Call the getter if it's safe.
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return exports.hasSafeGetter(desc) ? desc.get.call(root).return : undefined;
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}
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aObj = aObj.proto;
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} while (aObj);
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} catch (e) {
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// If anything goes wrong report the error and return undefined.
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exports.reportException("getProperty", e);
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}
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return undefined;
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};
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/**
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* Determines if a descriptor has a getter which doesn't call into JavaScript.
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*
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* @param Object aDesc
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* The descriptor to check for a safe getter.
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* @return Boolean
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* Whether a safe getter was found.
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*/
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exports.hasSafeGetter = function hasSafeGetter(aDesc) {
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let fn = aDesc.get;
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return fn && fn.callable && fn.class == "Function" && fn.script === undefined;
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};
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/**
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* Check if it is safe to read properties and execute methods from the given JS
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* object. Safety is defined as being protected from unintended code execution
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* from content scripts (or cross-compartment code).
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*
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* See bugs 945920 and 946752 for discussion.
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*
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* @type Object aObj
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* The object to check.
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* @return Boolean
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* True if it is safe to read properties from aObj, or false otherwise.
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*/
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exports.isSafeJSObject = function isSafeJSObject(aObj) {
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// If we are running on a worker thread, Cu is not available. In this case,
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// we always return false, just to be on the safe side.
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if (isWorker) {
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return false;
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}
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if (Cu.getGlobalForObject(aObj) ==
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Cu.getGlobalForObject(exports.isSafeJSObject)) {
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return true; // aObj is not a cross-compartment wrapper.
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}
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let principal = Cu.getObjectPrincipal(aObj);
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if (Services.scriptSecurityManager.isSystemPrincipal(principal)) {
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return true; // allow chrome objects
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}
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return Cu.isXrayWrapper(aObj);
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};
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exports.dumpn = function dumpn(str) {
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if (exports.dumpn.wantLogging) {
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dump("DBG-SERVER: " + str + "\n");
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}
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}
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// We want wantLogging to be writable. The exports object is frozen by the
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// loader, so define it on dumpn instead.
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exports.dumpn.wantLogging = false;
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/**
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* A verbose logger for low-level tracing.
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*/
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exports.dumpv = function(msg) {
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if (exports.dumpv.wantVerbose) {
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exports.dumpn(msg);
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}
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};
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// We want wantLogging to be writable. The exports object is frozen by the
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// loader, so define it on dumpn instead.
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exports.dumpv.wantVerbose = false;
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exports.dbg_assert = function dbg_assert(cond, e) {
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if (!cond) {
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return e;
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}
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}
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/**
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* Utility function for updating an object with the properties of another
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* object.
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*
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* @param aTarget Object
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* The object being updated.
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* @param aNewAttrs Object
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* The new attributes being set on the target.
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*/
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exports.update = function update(aTarget, aNewAttrs) {
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for (let key in aNewAttrs) {
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let desc = Object.getOwnPropertyDescriptor(aNewAttrs, key);
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if (desc) {
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Object.defineProperty(aTarget, key, desc);
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}
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}
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}
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/**
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* Defines a getter on a specified object that will be created upon first use.
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*
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* @param aObject
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* The object to define the lazy getter on.
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* @param aName
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* The name of the getter to define on aObject.
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* @param aLambda
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* A function that returns what the getter should return. This will
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* only ever be called once.
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*/
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exports.defineLazyGetter = function defineLazyGetter(aObject, aName, aLambda) {
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Object.defineProperty(aObject, aName, {
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get: function () {
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delete aObject[aName];
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return aObject[aName] = aLambda.apply(aObject);
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},
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configurable: true,
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enumerable: true
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});
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};
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/**
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* Defines a getter on a specified object for a module. The module will not
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* be imported until first use.
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*
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* @param aObject
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* The object to define the lazy getter on.
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* @param aName
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* The name of the getter to define on aObject for the module.
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* @param aResource
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* The URL used to obtain the module.
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* @param aSymbol
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* The name of the symbol exported by the module.
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* This parameter is optional and defaults to aName.
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*/
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exports.defineLazyModuleGetter = function defineLazyModuleGetter(aObject, aName,
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aResource,
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aSymbol)
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{
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this.defineLazyGetter(aObject, aName, function XPCU_moduleLambda() {
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var temp = {};
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Cu.import(aResource, temp);
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return temp[aSymbol || aName];
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});
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};
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