1 files changed, 62 insertions, 0 deletions
diff --git a/dom/localstorage/LSWriteOptimizerImpl.h b/dom/localstorage/LSWriteOptimizerImpl.h
new file mode 100644
index 0000000000..32ccff6c63
--- /dev/null
+++ b/dom/localstorage/LSWriteOptimizerImpl.h
@@ -0,0 +1,62 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+#ifndef mozilla_dom_localstorage_LSWriteOptimizerImpl_h
+#define mozilla_dom_localstorage_LSWriteOptimizerImpl_h
+
+#include "LSWriteOptimizer.h"
+
+namespace mozilla::dom {
+
+template <typename T, typename U>
+void LSWriteOptimizer<T, U>::InsertItem(const nsAString& aKey, const T& aValue,
+                                        int64_t aDelta) {
+  AssertIsOnOwningThread();
+
+  mWriteInfos.WithEntryHandle(aKey, [&](auto&& entry) {
+    if (entry && entry.Data()->GetType() == WriteInfo::DeleteItem) {
+      // We could just simply replace the deletion with ordinary update, but
+      // that would preserve item's original position/index. Imagine a case when
+      // we have only one existing key k1. Now let's create a new optimizer and
+      // remove k1, add k2 and add k1 back. The final order should be k2, k1
+      // (ordinary update would produce k1, k2). So we need to differentiate
+      // between normal update and "optimized" update which resulted from a
+      // deletion followed by an insertion. We use the UpdateWithMove flag for
+      // this.
+
+      entry.Update(MakeUnique<UpdateItemInfo>(NextSerialNumber(), aKey, aValue,
+                                              /* aUpdateWithMove */ true));
+    } else {
+      entry.InsertOrUpdate(
+          MakeUnique<InsertItemInfo>(NextSerialNumber(), aKey, aValue));
+    }
+  });
+
+  mTotalDelta += aDelta;
+}
+
+template <typename T, typename U>
+void LSWriteOptimizer<T, U>::UpdateItem(const nsAString& aKey, const T& aValue,
+                                        int64_t aDelta) {
+  AssertIsOnOwningThread();
+
+  mWriteInfos.WithEntryHandle(aKey, [&](auto&& entry) {
+    if (entry && entry.Data()->GetType() == WriteInfo::InsertItem) {
+      entry.Update(
+          MakeUnique<InsertItemInfo>(NextSerialNumber(), aKey, aValue));
+    } else {
+      entry.InsertOrUpdate(
+          MakeUnique<UpdateItemInfo>(NextSerialNumber(), aKey, aValue,
+                                     /* aUpdateWithMove */ false));
+    }
+  });
+
+  mTotalDelta += aDelta;
+}
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_localstorage_LSWriteOptimizerImpl_h