Quelle perf.js Sprache: JAVA

/* 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/. */
"use strict";

const { Actor } = require("resource://devtools/shared/protocol.js");
const { perfSpec } = require("resource://devtools/shared/specs/perf.js");

loader.lazyRequireGetter(
  this,
  "RecordingUtils",
  "resource://devtools/shared/performance-new/recording-utils.js"
);

// Some platforms are built without the Gecko Profiler.
const IS_SUPPORTED_PLATFORM = "nsIProfiler" in Ci;

/**
* The PerfActor wraps the Gecko Profiler interface (aka Services.profiler).
*/
exports.PerfActor = class PerfActor extends Actor {
  constructor(conn) {
    super(conn, perfSpec);

    // Only setup the observers on a supported platform.
    if (IS_SUPPORTED_PLATFORM) {
      this._observer = {
        observe: this._observe.bind(this),
      };
      Services.obs.addObserver(this._observer, "profiler-started");
      Services.obs.addObserver(this._observer, "profiler-stopped");
    }
  }

  destroy() {
    super.destroy();

    if (!IS_SUPPORTED_PLATFORM) {
      return;
    }
    Services.obs.removeObserver(this._observer, "profiler-started");
    Services.obs.removeObserver(this._observer, "profiler-stopped");
  }

  startProfiler(options) {
    if (!IS_SUPPORTED_PLATFORM) {
      return false;
    }

    // For a quick implementation, decide on some default values. These may need
    // to be tweaked or made configurable as needed.
    const settings = {
      entries: options.entries || 1000000,
      duration: options.duration || 0,
      interval: options.interval || 1,
      features: options.features || [
        "js",
        "stackwalk",
        "cpu",
        "responsiveness",
        "memory",
      ],
      threads: options.threads || ["GeckoMain", "Compositor"],
      activeTabID: RecordingUtils.getActiveBrowserID(),
    };

    try {
      // This can throw an error if the profiler is in the wrong state.
      Services.profiler.StartProfiler(
        settings.entries,
        settings.interval,
        settings.features,
        settings.threads,
        settings.activeTabID,
        settings.duration
      );
    } catch (e) {
      // In case any errors get triggered, bailout with a false.
      return false;
    }

    return true;
  }

  stopProfilerAndDiscardProfile() {
    if (!IS_SUPPORTED_PLATFORM) {
      return;
    }
    Services.profiler.StopProfiler();
  }

  /**
   * @type {string} debugPath
   * @type {string} breakpadId
   * @returns {Promise<[number[], number[], number[]]>}
   */
  async getSymbolTable(debugPath, breakpadId) {
    const [addr, index, buffer] = await Services.profiler.getSymbolTable(
      debugPath,
      breakpadId
    );
    // The protocol does not support the transfer of typed arrays, so we convert
    // these typed arrays to plain JS arrays of numbers now.
    // Our return value type is declared as "array:array:number".
    return [Array.from(addr), Array.from(index), Array.from(buffer)];
  }

  async getProfileAndStopProfiler() {
    if (!IS_SUPPORTED_PLATFORM) {
      return null;
    }

    // Pause profiler before we collect the profile, so that we don't capture
    // more samples while the parent process or android threads wait for subprocess profiles.
    Services.profiler.Pause();

    let profile;
    try {
      // Attempt to pull out the data.
      profile = await Services.profiler.getProfileDataAsync();

      if (Object.keys(profile).length === 0) {
        console.error(
          "An empty object was received from getProfileDataAsync.getProfileDataAsync(), " +
            "meaning that a profile could not successfully be serialized and captured."
        );
        profile = null;
      }
    } catch (e) {
      // Explicitly set the profile to null if there as an error.
      profile = null;
      console.error(`There was an error fetching a profile`, e);
    }

    // Stop and discard the buffers.
    Services.profiler.StopProfiler();

    // Returns a profile when successful, and null when there is an error.
    return profile;
  }

  isActive() {
    if (!IS_SUPPORTED_PLATFORM) {
      return false;
    }
    return Services.profiler.IsActive();
  }

  isSupportedPlatform() {
    return IS_SUPPORTED_PLATFORM;
  }

  /**
   * Watch for events that happen within the browser. These can affect the
   * current availability and state of the Gecko Profiler.
   */
  _observe(subject, topic, _data) {
    // Note! If emitting new events make sure and update the list of bridged
    // events in the perf actor.
    switch (topic) {
      case "profiler-started": {
        const param = subject.QueryInterface(Ci.nsIProfilerStartParams);
        this.emit(
          topic,
          param.entries,
          param.interval,
          param.features,
          param.duration,
          param.activeTabID
        );
        break;
      }
      case "profiler-stopped":
        this.emit(topic);
        break;
    }
  }

  /**
   * Lists the supported features of the profiler for the current browser.
   * @returns {string[]}
   */
  getSupportedFeatures() {
    if (!IS_SUPPORTED_PLATFORM) {
      return [];
    }
    return Services.profiler.GetFeatures();
  }
};

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