1 files changed, 104 insertions, 0 deletions
diff --git a/toolkit/components/telemetry/pings/UninstallPing.jsm b/toolkit/components/telemetry/pings/UninstallPing.jsm
new file mode 100644
index 0000000000..a69438cfc0
--- /dev/null
+++ b/toolkit/components/telemetry/pings/UninstallPing.jsm
@@ -0,0 +1,104 @@
+/* -*- js-indent-level: 2; indent-tabs-mode: nil -*- */
+/* 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";
+
+ChromeUtils.import("resource://gre/modules/Services.jsm", this);
+
+var EXPORTED_SYMBOLS = ["UninstallPing"];
+
+/**
+ * The Windows-only "uninstall" ping, which is saved to disk for the uninstaller to find.
+ * The ping is actually assembled by TelemetryControllerParent.saveUninstallPing().
+ */
+var UninstallPing = {
+  /**
+   * Maximum number of other installs to count (see
+   * toolkit/components/telemetry/docs/data/uninstall-ping.rst for motivation)
+   */
+  MAX_OTHER_INSTALLS: 11,
+
+  /**
+   * Count other installs of this app, based on the values in the TaskBarIDs registry key.
+   *
+   */
+  getOtherInstallsCount(rootKey) {
+    // This is somewhat more complicated than just counting the number of values on the key:
+    // 1) the same install can be listed in both HKCU and HKLM
+    // 2) the current path may not be listed
+    //
+    // The strategy is to add all paths to a Set (to deduplicate) and use that size.
+
+    // Add the names of the values under `rootKey\subKey` to `set`, until the set has `maxCount`.
+    // All strings are lower cased first, as Windows paths are not case-sensitive.
+    function collectValues(rootKey, wowFlag, subKey, set, maxCount) {
+      if (set.size >= maxCount) {
+        return;
+      }
+
+      const key = Cc["@mozilla.org/windows-registry-key;1"].createInstance(
+        Ci.nsIWindowsRegKey
+      );
+
+      try {
+        key.open(rootKey, subKey, key.ACCESS_READ | wowFlag);
+      } catch (_e) {
+        // The key may not exist, ignore.
+        // (nsWindowsRegKey::Open doesn't provide detailed error codes)
+        return;
+      }
+      const valueCount = key.valueCount;
+
+      try {
+        for (let i = 0; i < valueCount && set.size < maxCount; ++i) {
+          set.add(key.getValueName(i).toLowerCase());
+        }
+      } finally {
+        key.close();
+      }
+    }
+
+    const subKeyName = `Software\\Mozilla\\${Services.appinfo.name}\\TaskBarIDs`;
+
+    const paths = new Set();
+
+    // The current install path may not have a value in TaskBarIDs. It is simpler to
+    // pre-add it and always include it in the total, than to check for it everywhere and
+    // sometimes include it.
+    paths.add(Services.dirsvc.get("GreBinD", Ci.nsIFile).path.toLowerCase());
+
+    const initialPathsCount = paths.size;
+    const maxPathsCount = initialPathsCount + this.MAX_OTHER_INSTALLS;
+
+    // First collect from HKLM for both 32-bit and 64-bit installs regardless of the architecture
+    // of the current application.
+    for (const wowFlag of [
+      Ci.nsIWindowsRegKey.WOW64_32,
+      Ci.nsIWindowsRegKey.WOW64_64,
+    ]) {
+      collectValues(
+        Ci.nsIWindowsRegKey.ROOT_KEY_LOCAL_MACHINE,
+        wowFlag,
+        subKeyName,
+        paths,
+        maxPathsCount
+      );
+    }
+
+    // Then collect from HKCU.
+    // HKCU\Software is shared between 32 and 64 so nothing special is needed for WOW64,
+    // ref https://docs.microsoft.com/en-us/windows/win32/winprog64/shared-registry-keys
+    collectValues(
+      Ci.nsIWindowsRegKey.ROOT_KEY_CURRENT_USER,
+      0 /* wowFlag */,
+      subKeyName,
+      paths,
+      maxPathsCount
+    );
+
+    // Subtract our pre-added path, which is not an "other" install.
+    return paths.size - initialPathsCount;
+  },
+};