1 files changed, 102 insertions, 0 deletions
diff --git a/dom/svg/nsSVGAttrTearoffTable.h b/dom/svg/nsSVGAttrTearoffTable.h
new file mode 100644
index 000000000..ff907caa2
--- /dev/null
+++ b/dom/svg/nsSVGAttrTearoffTable.h
@@ -0,0 +1,102 @@
+/* -*- 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 NS_SVGATTRTEAROFFTABLE_H_
+#define NS_SVGATTRTEAROFFTABLE_H_
+
+#include "nsDataHashtable.h"
+#include "nsDebug.h"
+#include "nsHashKeys.h"
+
+/**
+ * Global hashmap to associate internal SVG data types (e.g. nsSVGLength2) with
+ * DOM tear-off objects (e.g. nsIDOMSVGLength). This allows us to always return
+ * the same object for subsequent requests for DOM objects.
+ *
+ * We don't keep an owning reference to the tear-off objects so they are
+ * responsible for removing themselves from this table when they die.
+ */
+template<class SimpleType, class TearoffType>
+class nsSVGAttrTearoffTable
+{
+public:
+#ifdef DEBUG
+  ~nsSVGAttrTearoffTable()
+  {
+    MOZ_ASSERT(!mTable, "Tear-off objects remain in hashtable at shutdown.");
+  }
+#endif
+
+  TearoffType* GetTearoff(SimpleType* aSimple);
+
+  void AddTearoff(SimpleType* aSimple, TearoffType* aTearoff);
+
+  void RemoveTearoff(SimpleType* aSimple);
+
+private:
+  typedef nsPtrHashKey<SimpleType> SimpleTypePtrKey;
+  typedef nsDataHashtable<SimpleTypePtrKey, TearoffType* > TearoffTable;
+
+  TearoffTable* mTable;
+};
+
+template<class SimpleType, class TearoffType>
+TearoffType*
+nsSVGAttrTearoffTable<SimpleType, TearoffType>::GetTearoff(SimpleType* aSimple)
+{
+  if (!mTable)
+    return nullptr;
+
+  TearoffType *tearoff = nullptr;
+
+#ifdef DEBUG
+  bool found =
+#endif
+    mTable->Get(aSimple, &tearoff);
+  MOZ_ASSERT(!found || tearoff,
+             "null pointer stored in attribute tear-off map");
+
+  return tearoff;
+}
+
+template<class SimpleType, class TearoffType>
+void
+nsSVGAttrTearoffTable<SimpleType, TearoffType>::AddTearoff(SimpleType* aSimple,
+                                                          TearoffType* aTearoff)
+{
+  if (!mTable) {
+    mTable = new TearoffTable;
+  }
+
+  // We shouldn't be adding a tear-off if there already is one. If that happens,
+  // something is wrong.
+  if (mTable->Get(aSimple, nullptr)) {
+    MOZ_ASSERT(false, "There is already a tear-off for this object.");
+    return;
+  }
+
+  mTable->Put(aSimple, aTearoff);
+}
+
+template<class SimpleType, class TearoffType>
+void
+nsSVGAttrTearoffTable<SimpleType, TearoffType>::RemoveTearoff(
+    SimpleType* aSimple)
+{
+  if (!mTable) {
+    // Perhaps something happened in between creating the SimpleType object and
+    // registering it
+    return;
+  }
+
+  mTable->Remove(aSimple);
+  if (mTable->Count() == 0) {
+    delete mTable;
+    mTable = nullptr;
+  }
+}
+
+#endif // NS_SVGATTRTEAROFFTABLE_H_