1 files changed, 91 insertions, 0 deletions
diff --git a/toolkit/components/utils/WindowsInstallsInfo.sys.mjs b/toolkit/components/utils/WindowsInstallsInfo.sys.mjs
new file mode 100644
index 0000000000..b599687e6c
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+++ b/toolkit/components/utils/WindowsInstallsInfo.sys.mjs
@@ -0,0 +1,91 @@
+/* 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/. */
+
+export var WindowsInstallsInfo = {
+  /**
+   * Retrieve install paths of this app, based on the values in the TaskBarIDs registry key.
+   *
+   * Installs from unarchived packages do not have a TaskBarID registry key and
+   * therefore won't appear in the result.
+   *
+   * @param {Number} [limit] Optional, maximum number of installation paths to count.
+            Defaults to 1024.
+   * @param {Set} [exclude] Optional, an Set of paths to exclude from the count.
+   * @returns {Set} Set of install paths, lower cased.
+   */
+  getInstallPaths(limit = 1024, exclude = new Set()) {
+    // This is somewhat more complicated than just collecting all values because
+    // the same install can be listed in both HKCU and HKLM.  The strategy is to
+    // add all paths to a Set to deduplicate.
+
+    const lcExclude = new Set();
+    exclude.forEach(p => lcExclude.add(p.toLowerCase()));
+
+    // Add the names of the values under `rootKey\subKey` to `set`.
+    // All strings are lower cased first, as Windows paths are not case-sensitive.
+    function collectValues(rootKey, wowFlag, subKey, set) {
+      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; ++i) {
+          const path = key.getValueName(i).toLowerCase();
+          if (!lcExclude.has(path)) {
+            set.add(path);
+          }
+          if (set.size >= limit) {
+            break;
+          }
+        }
+      } finally {
+        key.close();
+      }
+    }
+
+    const subKeyName = `Software\\Mozilla\\${Services.appinfo.name}\\TaskBarIDs`;
+
+    const paths = new Set();
+
+    // 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
+      );
+      if (paths.size >= limit) {
+        break;
+      }
+    }
+
+    if (paths.size < limit) {
+      // 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
+      );
+    }
+
+    return paths;
+  },
+};