1 files changed, 47 insertions, 0 deletions
diff --git a/layout/style/ShadowParts.h b/layout/style/ShadowParts.h
new file mode 100644
index 0000000000..3cfe1f6ad1
--- /dev/null
+++ b/layout/style/ShadowParts.h
@@ -0,0 +1,47 @@
+/* -*- 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_ShadowParts_h
+#define mozilla_ShadowParts_h
+
+#include "nsAtom.h"
+#include "nsTHashtable.h"
+#include "nsClassHashtable.h"
+#include "nsRefPtrHashtable.h"
+#include "nsStringFwd.h"
+
+namespace mozilla {
+
+class ShadowParts final {
+ public:
+  ShadowParts(ShadowParts&&) = default;
+  ShadowParts(const ShadowParts&) = delete;
+  static ShadowParts Parse(const nsAString&);
+
+  using PartList = AutoTArray<RefPtr<nsAtom>, 1>;
+
+  PartList* Get(nsAtom* aName) const { return mMappings.Get(aName); }
+
+  nsAtom* GetReverse(nsAtom* aName) const {
+    return mReverseMappings.GetWeak(aName);
+  }
+
+#ifdef DEBUG
+  void Dump() const;
+#endif
+
+ private:
+  ShadowParts() = default;
+
+  // TODO(emilio): If the two hashtables take a lot of memory we should consider
+  // just using an nsTArray<Pair<>> or something.
+  nsClassHashtable<nsRefPtrHashKey<nsAtom>, PartList> mMappings;
+  nsRefPtrHashtable<nsRefPtrHashKey<nsAtom>, nsAtom> mReverseMappings;
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_ShadowParts_h