Bug 1698098 - Add nsBaseHashtable::Clone methods. r=xpcom-reviewers,nika

Differential Revision: https://phabricator.services.mozilla.com/D106883

xpcom/ds/nsBaseHashtable.h

@@ -878,6 +878,26 @@ class nsBaseHashtable
   }
 
   using nsTHashtable<EntryType>::MarkImmutable;
+
+  /**
+   * Makes a clone of this hashtable by copying all entries. This requires
+   * KeyType and DataType to be copy-constructible.
+   */
+  nsBaseHashtable Clone() const { return CloneAs<nsBaseHashtable>(); }
+
+ protected:
+  template <typename T>
+  T CloneAs() const {
+    static_assert(std::is_base_of_v<nsBaseHashtable, T>);
+    // XXX This can probably be optimized, see Bug 1694368.
+    T result(Count());
+    for (const auto& srcEntry : *this) {
+      result.WithEntryHandle(srcEntry.GetKey(), [&](auto&& dstEntry) {
+        dstEntry.Insert(srcEntry.GetData());
+      });
+    }
+    return result;
+  }
 };
 
 //

xpcom/ds/nsRefCountedHashtable.h

@@ -89,6 +89,10 @@ class nsRefCountedHashtable
    * @return true if an entry for aKey was found (and removed)
    */
   inline bool Remove(KeyType aKey, RawPointerType* aData = nullptr);
+
+  nsRefCountedHashtable Clone() const {
+    return this->template CloneAs<nsRefCountedHashtable>();
+  }
 };
 
 template <typename K, typename T>

xpcom/tests/gtest/TestHashtables.cpp

@@ -1531,3 +1531,51 @@ TEST(Hashtables, RefPtrHashtable)
   }
   ASSERT_EQ(count, uint32_t(0));
 }
+
+TEST(Hashtables, RefPtrHashtable_Clone)
+{
+  // check a RefPtr-hashtable
+  nsRefPtrHashtable<nsCStringHashKey, TestUniCharRefCounted> EntToUniClass(
+      ENTITY_COUNT);
+
+  for (auto& entity : gEntities) {
+    EntToUniClass.InsertOrUpdate(
+        nsDependentCString(entity.mStr),
+        MakeRefPtr<TestUniCharRefCounted>(entity.mUnicode));
+  }
+
+  auto clone = EntToUniClass.Clone();
+  static_assert(std::is_same_v<decltype(clone), decltype(EntToUniClass)>);
+
+  EXPECT_EQ(clone.Count(), EntToUniClass.Count());
+
+  for (const auto& entry : EntToUniClass) {
+    auto cloneEntry = clone.Lookup(entry.GetKey());
+
+    EXPECT_TRUE(cloneEntry);
+    EXPECT_EQ(cloneEntry.Data(), entry.GetWeak());
+  }
+}
+
+TEST(Hashtables, Clone)
+{
+  static constexpr uint64_t count = 10;
+
+  nsTHashMap<nsUint64HashKey, uint64_t> table;
+  for (uint64_t i = 0; i < count; i++) {
+    table.InsertOrUpdate(42 + i, i);
+  }
+
+  auto clone = table.Clone();
+
+  static_assert(std::is_same_v<decltype(clone), decltype(table)>);
+
+  EXPECT_EQ(clone.Count(), table.Count());
+
+  for (const auto& entry : table) {
+    auto cloneEntry = clone.Lookup(entry.GetKey());
+
+    EXPECT_TRUE(cloneEntry);
+    EXPECT_EQ(cloneEntry.Data(), entry.GetData());
+  }
+}