114 lines
3.2 KiB
JavaScript
114 lines
3.2 KiB
JavaScript
/* globals Services */
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"use strict";
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let usablePerfObj;
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let Cu;
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const isRunningInChrome = typeof Window === "undefined";
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/* istanbul ignore if */
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if (isRunningInChrome) {
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Cu = Components.utils;
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} else {
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Cu = {import() {}};
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}
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Cu.import("resource://gre/modules/Services.jsm");
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/* istanbul ignore if */
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if (isRunningInChrome) {
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// Borrow the high-resolution timer from the hidden window....
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usablePerfObj = Services.appShell.hiddenDOMWindow.performance;
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} else { // we must be running in content space
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usablePerfObj = performance;
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}
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this._PerfService = function _PerfService(options) {
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// For testing, so that we can use a fake Window.performance object with
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// known state.
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if (options && options.performanceObj) {
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this._perf = options.performanceObj;
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} else {
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this._perf = usablePerfObj;
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}
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};
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_PerfService.prototype = {
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/**
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* Calls the underlying mark() method on the appropriate Window.performance
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* object to add a mark with the given name to the appropriate performance
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* timeline.
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*
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* @param {String} name the name to give the current mark
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* @return {void}
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*/
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mark: function mark(str) {
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this._perf.mark(str);
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},
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/**
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* Calls the underlying getEntriesByName on the appropriate Window.performance
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* object.
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*
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* @param {String} name
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* @param {String} type eg "mark"
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* @return {Array} Performance* objects
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*/
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getEntriesByName: function getEntriesByName(name, type) {
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return this._perf.getEntriesByName(name, type);
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},
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/**
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* The timeOrigin property from the appropriate performance object.
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* Used to ensure that timestamps from the add-on code and the content code
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* are comparable.
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*
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* @return {Number} A double of milliseconds with a precision of 0.5us.
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*/
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get timeOrigin() {
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return this._perf.timeOrigin;
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},
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/**
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* Returns the "absolute" version of performance.now(), i.e. one that
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* based on the timeOrigin of the XUL hiddenwindow.
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*
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* @return {Number}
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*/
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absNow: function absNow() {
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return this.timeOrigin + this._perf.now();
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},
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/**
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* This returns the absolute startTime from the most recent performance.mark()
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* with the given name.
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*
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* @param {String} name the name to lookup the start time for
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*
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* @return {Number} the returned start time, as a DOMHighResTimeStamp
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*
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* @throws {Error} "No Marks with the name ..." if none are available
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*
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* @note Always surround calls to this by try/catch. Otherwise your code
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* may fail when the `privacy.resistFingerprinting` pref is true. When
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* this pref is set, all attempts to get marks will likely fail, which will
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* cause this method to throw.
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*
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* See [bug 1369303](https://bugzilla.mozilla.org/show_bug.cgi?id=1369303)
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* for more info.
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*/
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getMostRecentAbsMarkStartByName(name) {
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let entries = this.getEntriesByName(name, "mark");
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if (!entries.length) {
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throw new Error(`No marks with the name ${name}`);
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}
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let mostRecentEntry = entries[entries.length - 1];
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return this._perf.timeOrigin + mostRecentEntry.startTime;
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}
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};
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this.perfService = new _PerfService();
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this.EXPORTED_SYMBOLS = ["_PerfService", "perfService"];
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