dom/svg/SVGAttrTearoffTable.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef DOM_SVG_SVGATTRTEAROFFTABLE_H_
   8 #define DOM_SVG_SVGATTRTEAROFFTABLE_H_
   9
  10 #include "mozilla/DebugOnly.h"
  11 #include "mozilla/StaticPtr.h"
  12 #include "nsTHashMap.h"
  13 #include "nsDebug.h"
  14 #include "nsHashKeys.h"
  15
  16 namespace mozilla {
  17
  18 /**
  19  * Global hashmap to associate internal SVG data types (e.g. SVGAnimatedLength)
  20  * with DOM tear-off objects (e.g. DOMSVGLength). This allows us to always
  21  * return the same object for subsequent requests for DOM objects.
  22  *
  23  * We don't keep an owning reference to the tear-off objects so they are
  24  * responsible for removing themselves from this table when they die.
  25  */
  26 template <class SimpleType, class TearoffType>
  27 class SVGAttrTearoffTable {
  28  public:
  29 #ifdef DEBUG
  30   ~SVGAttrTearoffTable() {
  31     NS_ASSERTION(!mTable, "Tear-off objects remain in hashtable at shutdown.");
  32   }
  33 #endif
  34
  35   TearoffType* GetTearoff(SimpleType* aSimple);
  36
  37   void AddTearoff(SimpleType* aSimple, TearoffType* aTearoff);
  38
  39   void RemoveTearoff(SimpleType* aSimple);
  40
  41  private:
  42   using SimpleTypePtrKey = nsPtrHashKey<SimpleType>;
  43   using TearoffTable = nsTHashMap<SimpleTypePtrKey, TearoffType*>;
  44
  45   StaticAutoPtr<TearoffTable> mTable;
  46 };
  47
  48 template <class SimpleType, class TearoffType>
  49 TearoffType* SVGAttrTearoffTable<SimpleType, TearoffType>::GetTearoff(
  50     SimpleType* aSimple) {
  51   if (!mTable) {
  52     return nullptr;
  53   }
  54
  55   TearoffType* tearoff = nullptr;
  56
  57   DebugOnly<bool> found = mTable->Get(aSimple, &tearoff);
  58   MOZ_ASSERT(!found || tearoff,
  59              "null pointer stored in attribute tear-off map");
  60
  61   return tearoff;
  62 }
  63
  64 template <class SimpleType, class TearoffType>
  65 void SVGAttrTearoffTable<SimpleType, TearoffType>::AddTearoff(
  66     SimpleType* aSimple, TearoffType* aTearoff) {
  67   if (!mTable) {
  68     mTable = new TearoffTable();
  69   }
  70
  71   // We shouldn't be adding a tear-off if there already is one. If that happens,
  72   // something is wrong.
  73   if (mTable->Get(aSimple, nullptr)) {
  74     MOZ_ASSERT(false, "There is already a tear-off for this object.");
  75     return;
  76   }
  77
  78   mTable->InsertOrUpdate(aSimple, aTearoff);
  79 }
  80
  81 template <class SimpleType, class TearoffType>
  82 void SVGAttrTearoffTable<SimpleType, TearoffType>::RemoveTearoff(
  83     SimpleType* aSimple) {
  84   if (!mTable) {
  85     // Perhaps something happened in between creating the SimpleType object and
  86     // registering it
  87     return;
  88   }
  89
  90   mTable->Remove(aSimple);
  91   if (mTable->Count() == 0) {
  92     mTable = nullptr;
  93   }
  94 }
  95
  96 }  // namespace mozilla
  97
  98 #endif  // DOM_SVG_SVGATTRTEAROFFTABLE_H_