diff -r 000000000000 -r 6474c204b198 dom/bindings/MozMap.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/bindings/MozMap.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,132 @@
+/* -*- 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/. */
+
+/**
+ * Class for representing MozMap arguments.  This is an nsTHashtable
+ * under the hood, but we don't want to leak that implementation
+ * detail.
+ */
+
+#ifndef mozilla_dom_MozMap_h
+#define mozilla_dom_MozMap_h
+
+#include "nsTHashtable.h"
+#include "nsHashKeys.h"
+#include "nsStringGlue.h"
+#include "nsTArray.h"
+#include "mozilla/Move.h"
+
+namespace mozilla {
+namespace dom {
+
+namespace binding_detail {
+template<typename DataType>
+class MozMapEntry : public nsStringHashKey
+{
+public:
+  MozMapEntry(const nsAString* aKeyTypePointer)
+    : nsStringHashKey(aKeyTypePointer)
+  {
+  }
+
+  // Move constructor so we can do MozMaps of MozMaps.
+  MozMapEntry(MozMapEntry<DataType>&& aOther)
+    : nsStringHashKey(aOther),
+      mData(Move(aOther.mData))
+  {
+  }
+
+  DataType mData;
+};
+} // namespace binding_detail
+
+template<typename DataType>
+class MozMap : protected nsTHashtable<binding_detail::MozMapEntry<DataType>>
+{
+public:
+  typedef typename binding_detail::MozMapEntry<DataType> EntryType;
+  typedef nsTHashtable<EntryType> Base;
+  typedef MozMap<DataType> SelfType;
+
+  MozMap()
+  {
+  }
+
+  // Move constructor so we can do MozMap of MozMap.
+  MozMap(SelfType&& aOther) :
+    Base(Move(aOther))
+  {
+  }
+
+  // The return value is only safe to use until an AddEntry call.
+  const DataType& Get(const nsAString& aKey) const
+  {
+    const EntryType* ent = this->GetEntry(aKey);
+    MOZ_ASSERT(ent, "Why are you using a key we didn't claim to have?");
+    return ent->mData;
+  }
+
+  // The return value is only safe to use until an AddEntry call.
+  const DataType* GetIfExists(const nsAString& aKey) const
+  {
+    const EntryType* ent = this->GetEntry(aKey);
+    if (!ent) {
+      return nullptr;
+    }
+    return &ent->mData;
+  }
+
+  void GetKeys(nsTArray<nsString>& aKeys) const {
+    // Sadly, EnumerateEntries is not a const method
+    const_cast<SelfType*>(this)->EnumerateEntries(KeyEnumerator, &aKeys);
+  }
+
+  // XXXbz we expose this generic enumerator for tracing.  Otherwise we'd end up
+  // with a dependency on BindingUtils.h here for the SequenceTracer bits.
+  typedef PLDHashOperator (* Enumerator)(DataType* aValue, void* aClosure);
+  void EnumerateValues(Enumerator aEnumerator, void *aClosure)
+  {
+    ValueEnumClosure args = { aEnumerator, aClosure };
+    this->EnumerateEntries(ValueEnumerator, &args);
+  }
+
+  DataType* AddEntry(const nsAString& aKey) NS_WARN_UNUSED_RESULT
+  {
+    // XXXbz can't just use fallible_t() because our superclass has a
+    // private typedef by that name.
+    EntryType* ent = this->PutEntry(aKey, mozilla::fallible_t());
+    if (!ent) {
+      return nullptr;
+    }
+    return &ent->mData;
+  }
+
+private:
+  static PLDHashOperator
+  KeyEnumerator(EntryType* aEntry, void* aClosure)
+  {
+    nsTArray<nsString>& keys = *static_cast<nsTArray<nsString>*>(aClosure);
+    keys.AppendElement(aEntry->GetKey());
+    return PL_DHASH_NEXT;
+  }
+
+  struct ValueEnumClosure {
+    Enumerator mEnumerator;
+    void* mClosure;
+  };
+
+  static PLDHashOperator
+  ValueEnumerator(EntryType* aEntry, void* aClosure)
+  {
+    ValueEnumClosure* enumClosure = static_cast<ValueEnumClosure*>(aClosure);
+    return enumClosure->mEnumerator(&aEntry->mData, enumClosure->mClosure);
+  }
+};
+
+} // namespace dom
+} // namespace mozilla
+
+#endif // mozilla_dom_MozMap_h