1 files changed, 335 insertions, 0 deletions
diff --git a/toolkit/components/telemetry/TelemetryStopwatch.jsm b/toolkit/components/telemetry/TelemetryStopwatch.jsm
new file mode 100644
index 000000000..ab6c6eafb
--- /dev/null
+++ b/toolkit/components/telemetry/TelemetryStopwatch.jsm
@@ -0,0 +1,335 @@
+/* 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/. */
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cu = Components.utils;
+
+this.EXPORTED_SYMBOLS = ["TelemetryStopwatch"];
+
+Cu.import("resource://gre/modules/Log.jsm", this);
+var Telemetry = Cc["@mozilla.org/base/telemetry;1"]
+                  .getService(Ci.nsITelemetry);
+
+// Weak map does not allow using null objects as keys. These objects are used
+// as 'null' placeholders.
+const NULL_OBJECT = {};
+const NULL_KEY = {};
+
+/**
+ * Timers is a variation of a Map used for storing information about running
+ * Stopwatches. Timers has the following data structure:
+ *
+ * {
+ *    "HISTOGRAM_NAME": WeakMap {
+ *      Object || NULL_OBJECT: Map {
+ *        "KEY" || NULL_KEY: startTime
+ *        ...
+ *      }
+ *      ...
+ *    }
+ *    ...
+ * }
+ *
+ *
+ * @example
+ * // Stores current time for a keyed histogram "PLAYING_WITH_CUTE_ANIMALS".
+ * Timers.put("PLAYING_WITH_CUTE_ANIMALS", null, "CATS", Date.now());
+ *
+ * @example
+ * // Returns information about a simple Stopwatch.
+ * let startTime = Timers.get("PLAYING_WITH_CUTE_ANIMALS", null, "CATS");
+ */
+let Timers = {
+  _timers: new Map(),
+
+  _validTypes: function(histogram, obj, key) {
+    let nonEmptyString = value => {
+      return typeof value === "string" && value !== "" && value.length > 0;
+    };
+    return  nonEmptyString(histogram) &&
+            typeof obj == "object" &&
+           (key === NULL_KEY || nonEmptyString(key));
+  },
+
+  get: function(histogram, obj, key) {
+    key = key === null ? NULL_KEY : key;
+    obj = obj || NULL_OBJECT;
+
+    if (!this.has(histogram, obj, key)) {
+      return null;
+    }
+
+    return this._timers.get(histogram).get(obj).get(key);
+  },
+
+  put: function(histogram, obj, key, startTime) {
+    key = key === null ? NULL_KEY : key;
+    obj = obj || NULL_OBJECT;
+
+    if (!this._validTypes(histogram, obj, key)) {
+      return false;
+    }
+
+    let objectMap = this._timers.get(histogram) || new WeakMap();
+    let keyedInfo = objectMap.get(obj) || new Map();
+    keyedInfo.set(key, startTime);
+    objectMap.set(obj, keyedInfo);
+    this._timers.set(histogram, objectMap);
+    return true;
+  },
+
+  has: function(histogram, obj, key) {
+    key = key === null ? NULL_KEY : key;
+    obj = obj || NULL_OBJECT;
+
+    return this._timers.has(histogram) &&
+      this._timers.get(histogram).has(obj) &&
+      this._timers.get(histogram).get(obj).has(key);
+  },
+
+  delete: function(histogram, obj, key) {
+    key = key === null ? NULL_KEY : key;
+    obj = obj || NULL_OBJECT;
+
+    if (!this.has(histogram, obj, key)) {
+      return false;
+    }
+    let objectMap = this._timers.get(histogram);
+    let keyedInfo = objectMap.get(obj);
+    if (keyedInfo.size > 1) {
+      keyedInfo.delete(key);
+      return true;
+    }
+    objectMap.delete(obj);
+    // NOTE:
+    // We never delete empty objecMaps from this._timers because there is no
+    // nice solution for tracking the number of objects in a WeakMap.
+    // WeakMap is not enumerable, so we can't deterministically say when it's
+    // empty. We accept that trade-off here, given that entries for short-lived
+    // objects will go away when they are no longer referenced
+    return true;
+  }
+};
+
+this.TelemetryStopwatch = {
+  /**
+   * Starts a timer associated with a telemetry histogram. The timer can be
+   * directly associated with a histogram, or with a pair of a histogram and
+   * an object.
+   *
+   * @param {String} aHistogram - a string which must be a valid histogram name.
+   *
+   * @param {Object} aObj - Optional parameter. If specified, the timer is
+   *                        associated with this object, meaning that multiple
+   *                        timers for the same histogram may be run
+   *                        concurrently, as long as they are associated with
+   *                        different objects.
+   *
+   * @returns {Boolean} True if the timer was successfully started, false
+   *                    otherwise. If a timer already exists, it can't be
+   *                    started again, and the existing one will be cleared in
+   *                    order to avoid measurements errors.
+   */
+  start: function(aHistogram, aObj) {
+    return TelemetryStopwatchImpl.start(aHistogram, aObj, null);
+  },
+
+  /**
+   * Deletes the timer associated with a telemetry histogram. The timer can be
+   * directly associated with a histogram, or with a pair of a histogram and
+   * an object. Important: Only use this method when a legitimate cancellation
+   * should be done.
+   *
+  * @param {String} aHistogram - a string which must be a valid histogram name.
+   *
+   * @param {Object} aObj - Optional parameter. If specified, the timer is
+   *                        associated with this object, meaning that multiple
+   *                        timers or a same histogram may be run concurrently,
+   *                        as long as they are associated with different
+   *                        objects.
+   *
+   * @returns {Boolean} True if the timer exist and it was cleared, False
+   *                   otherwise.
+   */
+  cancel: function(aHistogram, aObj) {
+    return TelemetryStopwatchImpl.cancel(aHistogram, aObj, null);
+  },
+
+  /**
+   * Returns the elapsed time for a particular stopwatch. Primarily for
+   * debugging purposes. Must be called prior to finish.
+   *
+   * @param {String} aHistogram - a string which must be a valid histogram name.
+   *                              If an invalid name is given, the function will
+   *                              throw.
+   *
+   * @param (Object) aObj - Optional parameter which associates the histogram
+   *                        timer with the given object.
+   *
+   * @returns {Integer} time in milliseconds or -1 if the stopwatch was not
+   *                   found.
+   */
+  timeElapsed: function(aHistogram, aObj) {
+    return TelemetryStopwatchImpl.timeElapsed(aHistogram, aObj, null);
+  },
+
+  /**
+   * Stops the timer associated with the given histogram (and object),
+   * calculates the time delta between start and finish, and adds the value
+   * to the histogram.
+   *
+   * @param {String} aHistogram - a string which must be a valid histogram name.
+   *
+   * @param {Object} aObj - Optional parameter which associates the histogram
+   *                        timer with the given object.
+   *
+   * @returns {Boolean} True if the timer was succesfully stopped and the data
+   *                    was added to the histogram, False otherwise.
+   */
+  finish: function(aHistogram, aObj) {
+    return TelemetryStopwatchImpl.finish(aHistogram, aObj, null);
+  },
+
+  /**
+   * Starts a timer associated with a keyed telemetry histogram. The timer can
+   * be directly associated with a histogram and its key. Similarly to
+   * @see{TelemetryStopwatch.stat} the histogram and its key can be associated
+   * with an object. Each key may have multiple associated objects and each
+   * object can be associated with multiple keys.
+   *
+   * @param {String} aHistogram - a string which must be a valid histogram name.
+   *
+   * @param {String} aKey - a string which must be a valid histgram key.
+   *
+   * @param {Object} aObj - Optional parameter. If specified, the timer is
+   *                        associated with this object, meaning that multiple
+   *                        timers for the same histogram may be run
+   *                        concurrently,as long as they are associated with
+   *                        different objects.
+   *
+   * @returns {Boolean} True if the timer was successfully started, false
+   *                    otherwise. If a timer already exists, it can't be
+   *                    started again, and the existing one will be cleared in
+   *                    order to avoid measurements errors.
+   */
+  startKeyed: function(aHistogram, aKey, aObj) {
+    return TelemetryStopwatchImpl.start(aHistogram, aObj, aKey);
+  },
+
+  /**
+   * Deletes the timer associated with a keyed histogram. Important: Only use
+   * this method when a legitimate cancellation should be done.
+   *
+   * @param {String} aHistogram - a string which must be a valid histogram name.
+   *
+   * @param {String} aKey - a string which must be a valid histgram key.
+   *
+   * @param {Object} aObj - Optional parameter. If specified, the timer
+   *                        associated with this object is deleted.
+   *
+   * @return {Boolean} True if the timer exist and it was cleared, False
+   *                   otherwise.
+   */
+  cancelKeyed: function(aHistogram, aKey, aObj) {
+    return TelemetryStopwatchImpl.cancel(aHistogram, aObj, aKey);
+  },
+
+  /**
+   * Returns the elapsed time for a particular stopwatch. Primarily for
+   * debugging purposes. Must be called prior to finish.
+   *
+   * @param {String} aHistogram - a string which must be a valid histogram name.
+   *
+   * @param {String} aKey - a string which must be a valid histgram key.
+   *
+   * @param {Object} aObj - Optional parameter. If specified, the timer
+   *                        associated with this object is used to calculate
+   *                        the elapsed time.
+   *
+   * @return {Integer} time in milliseconds or -1 if the stopwatch was not
+   *                   found.
+   */
+  timeElapsedKeyed: function(aHistogram, aKey, aObj) {
+    return TelemetryStopwatchImpl.timeElapsed(aHistogram, aObj, aKey);
+  },
+
+  /**
+   * Stops the timer associated with the given keyed histogram (and object),
+   * calculates the time delta between start and finish, and adds the value
+   * to the keyed histogram.
+   *
+   * @param {String} aHistogram - a string which must be a valid histogram name.
+   *
+   * @param {String} aKey - a string which must be a valid histgram key.
+   *
+   * @param {Object} aObj - optional parameter which associates the histogram
+   *                        timer with the given object.
+   *
+   * @returns {Boolean} True if the timer was succesfully stopped and the data
+   *                   was added to the histogram, False otherwise.
+   */
+  finishKeyed: function(aHistogram, aKey, aObj) {
+    return TelemetryStopwatchImpl.finish(aHistogram, aObj, aKey);
+  }
+};
+
+this.TelemetryStopwatchImpl = {
+  start: function(histogram, object, key) {
+    if (Timers.has(histogram, object, key)) {
+      Timers.delete(histogram, object, key);
+      Cu.reportError(`TelemetryStopwatch: key "${histogram}" was already ` +
+                     "initialized");
+      return false;
+    }
+
+    return Timers.put(histogram, object, key, Components.utils.now());
+  },
+
+  cancel: function (histogram, object, key) {
+    return Timers.delete(histogram, object, key);
+  },
+
+  timeElapsed: function(histogram, object, key) {
+    let startTime = Timers.get(histogram, object, key);
+    if (startTime === null) {
+      Cu.reportError("TelemetryStopwatch: requesting elapsed time for " +
+                     `nonexisting stopwatch. Histogram: "${histogram}", ` +
+                     `key: "${key}"`);
+      return -1;
+    }
+
+    try {
+      let delta = Components.utils.now() - startTime
+      return Math.round(delta);
+    } catch (e) {
+      Cu.reportError("TelemetryStopwatch: failed to calculate elapsed time " +
+                     `for Histogram: "${histogram}", key: "${key}", ` +
+                     `exception: ${Log.exceptionStr(e)}`);
+      return -1;
+    }
+  },
+
+  finish: function(histogram, object, key) {
+    let delta = this.timeElapsed(histogram, object, key);
+    if (delta == -1) {
+      return false;
+    }
+
+    try {
+      if (key) {
+        Telemetry.getKeyedHistogramById(histogram).add(key, delta);
+      } else {
+        Telemetry.getHistogramById(histogram).add(delta);
+      }
+    } catch (e) {
+      Cu.reportError("TelemetryStopwatch: failed to update the Histogram " +
+                     `"${histogram}", using key: "${key}", ` +
+                     `exception: ${Log.exceptionStr(e)}`);
+      return false;
+    }
+
+    return Timers.delete(histogram, object, key);
+  }
+}