dom/base/IdentifierMapEntry.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 /*
   8  * Entry for the Document or ShadowRoot's identifier map.
   9  */
  10
  11 #ifndef mozilla_IdentifierMapEntry_h
  12 #define mozilla_IdentifierMapEntry_h
  13
  14 #include <utility>
  15
  16 #include "PLDHashTable.h"
  17 #include "mozilla/MemoryReporting.h"
  18 #include "mozilla/UniquePtr.h"
  19 #include "mozilla/dom/TreeOrderedArray.h"
  20 #include "nsAtom.h"
  21 #include "nsCOMPtr.h"
  22 #include "nsContentList.h"
  23 #include "nsHashKeys.h"
  24 #include "nsTArray.h"
  25 #include "nsTHashtable.h"
  26
  27 class nsIContent;
  28 class nsINode;
  29
  30 namespace mozilla {
  31 namespace dom {
  32 class Document;
  33 class Element;
  34 }  // namespace dom
  35
  36 /**
  37  * Right now our identifier map entries contain information for 'name'
  38  * and 'id' mappings of a given string. This is so that
  39  * nsHTMLDocument::ResolveName only has to do one hash lookup instead
  40  * of two. It's not clear whether this still matters for performance.
  41  *
  42  * We also store the document.all result list here. This is mainly so that
  43  * when all elements with the given ID are removed and we remove
  44  * the ID's IdentifierMapEntry, the document.all result is released too.
  45  * Perhaps the document.all results should have their own hashtable
  46  * in nsHTMLDocument.
  47  */
  48 class IdentifierMapEntry : public PLDHashEntryHdr {
  49   typedef dom::Document Document;
  50   typedef dom::Element Element;
  51
  52   /**
  53    * @see Document::IDTargetObserver, this is just here to avoid include hell.
  54    */
  55   typedef bool (*IDTargetObserver)(Element* aOldElement, Element* aNewelement,
  56                                    void* aData);
  57
  58  public:
  59   // We use DependentAtomOrString as our external key interface.  This allows
  60   // consumers to use an nsAString, for example, without forcing a copy.
  61   struct DependentAtomOrString final {
  62     MOZ_IMPLICIT DependentAtomOrString(nsAtom* aAtom)
  63         : mAtom(aAtom), mString(nullptr) {}
  64     MOZ_IMPLICIT DependentAtomOrString(const nsAString& aString)
  65         : mAtom(nullptr), mString(&aString) {}
  66     DependentAtomOrString(const DependentAtomOrString& aOther) = default;
  67
  68     nsAtom* mAtom;
  69     const nsAString* mString;
  70   };
  71
  72   typedef const DependentAtomOrString& KeyType;
  73   typedef const DependentAtomOrString* KeyTypePointer;
  74
  75   explicit IdentifierMapEntry(const DependentAtomOrString* aKey);
  76   IdentifierMapEntry(IdentifierMapEntry&& aOther) = default;
  77   ~IdentifierMapEntry() = default;
  78
  79   nsString GetKeyAsString() const {
  80     if (mKey.mAtom) {
  81       return nsAtomString(mKey.mAtom);
  82     }
  83
  84     return mKey.mString;
  85   }
  86
  87   bool KeyEquals(const KeyTypePointer aOtherKey) const {
  88     if (mKey.mAtom) {
  89       if (aOtherKey->mAtom) {
  90         return mKey.mAtom == aOtherKey->mAtom;
  91       }
  92
  93       return mKey.mAtom->Equals(*aOtherKey->mString);
  94     }
  95
  96     if (aOtherKey->mAtom) {
  97       return aOtherKey->mAtom->Equals(mKey.mString);
  98     }
  99
 100     return mKey.mString.Equals(*aOtherKey->mString);
 101   }
 102
 103   static KeyTypePointer KeyToPointer(KeyType aKey) { return &aKey; }
 104
 105   static PLDHashNumber HashKey(const KeyTypePointer aKey) {
 106     return aKey->mAtom ? aKey->mAtom->hash() : HashString(*aKey->mString);
 107   }
 108
 109   enum { ALLOW_MEMMOVE = false };
 110
 111   void AddNameElement(nsINode* aDocument, Element* aElement);
 112   void RemoveNameElement(Element* aElement);
 113   bool IsEmpty();
 114   nsBaseContentList* GetNameContentList() { return mNameContentList; }
 115   bool HasNameElement() const;
 116
 117   /**
 118    * Returns the element if we know the element associated with this
 119    * id. Otherwise returns null.
 120    */
 121   Element* GetIdElement() const { return mIdContentList->SafeElementAt(0); }
 122
 123   /**
 124    * Returns the list of all elements associated with this id.
 125    */
 126   const nsTArray<Element*>& GetIdElements() const { return mIdContentList; }
 127
 128   /**
 129    * If this entry has a non-null image element set (using SetImageElement),
 130    * the image element will be returned, otherwise the same as GetIdElement().
 131    */
 132   Element* GetImageIdElement() {
 133     return mImageElement ? mImageElement.get() : GetIdElement();
 134   }
 135
 136   /**
 137    * This can fire ID change callbacks.
 138    */
 139   void AddIdElement(Element* aElement);
 140   /**
 141    * This can fire ID change callbacks.
 142    */
 143   void RemoveIdElement(Element* aElement);
 144   /**
 145    * Set the image element override for this ID. This will be returned by
 146    * GetIdElement(true) if non-null.
 147    */
 148   void SetImageElement(Element* aElement);
 149   bool HasIdElementExposedAsHTMLDocumentProperty() const;
 150
 151   bool HasContentChangeCallback() { return mChangeCallbacks != nullptr; }
 152   void AddContentChangeCallback(IDTargetObserver aCallback, void* aData,
 153                                 bool aForImage);
 154   void RemoveContentChangeCallback(IDTargetObserver aCallback, void* aData,
 155                                    bool aForImage);
 156
 157   /**
 158    * Remove all elements and notify change listeners.
 159    */
 160   void ClearAndNotify();
 161
 162   void Traverse(nsCycleCollectionTraversalCallback* aCallback);
 163
 164   struct ChangeCallback {
 165     IDTargetObserver mCallback;
 166     void* mData;
 167     bool mForImage;
 168   };
 169
 170   struct ChangeCallbackEntry : public PLDHashEntryHdr {
 171     typedef const ChangeCallback KeyType;
 172     typedef const ChangeCallback* KeyTypePointer;
 173
 174     explicit ChangeCallbackEntry(const ChangeCallback* aKey) : mKey(*aKey) {}
 175     ChangeCallbackEntry(ChangeCallbackEntry&& aOther)
 176         : PLDHashEntryHdr(std::move(aOther)), mKey(std::move(aOther.mKey)) {}
 177
 178     KeyType GetKey() const { return mKey; }
 179     bool KeyEquals(KeyTypePointer aKey) const {
 180       return aKey->mCallback == mKey.mCallback && aKey->mData == mKey.mData &&
 181              aKey->mForImage == mKey.mForImage;
 182     }
 183
 184     static KeyTypePointer KeyToPointer(KeyType& aKey) { return &aKey; }
 185     static PLDHashNumber HashKey(KeyTypePointer aKey) {
 186       return HashGeneric(aKey->mCallback, aKey->mData);
 187     }
 188     enum { ALLOW_MEMMOVE = true };
 189
 190     ChangeCallback mKey;
 191   };
 192
 193   size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const;
 194
 195  private:
 196   // We use an OwningAtomOrString as our internal key storage.  It needs to own
 197   // the key string, whether in atom or string form.
 198   struct OwningAtomOrString final {
 199     OwningAtomOrString(const OwningAtomOrString& aOther) = delete;
 200     OwningAtomOrString(OwningAtomOrString&& aOther) = default;
 201
 202     explicit OwningAtomOrString(const DependentAtomOrString& aOther)
 203         // aOther may have a null mString, so jump through a bit of a hoop in
 204         // that case.  I wish there were a way to just default-initialize
 205         // mString in that situation...  We could also make mString not const
 206         // and only assign to it if aOther.mString is not null, but having it be
 207         // const is nice.
 208         : mAtom(aOther.mAtom),
 209           mString(aOther.mString ? *aOther.mString : u""_ns) {}
 210
 211     RefPtr<nsAtom> mAtom;
 212     nsString mString;
 213   };
 214
 215   IdentifierMapEntry(const IdentifierMapEntry& aOther) = delete;
 216   IdentifierMapEntry& operator=(const IdentifierMapEntry& aOther) = delete;
 217
 218   void FireChangeCallbacks(Element* aOldElement, Element* aNewElement,
 219                            bool aImageOnly = false);
 220
 221   OwningAtomOrString mKey;
 222   dom::TreeOrderedArray<Element> mIdContentList;
 223   RefPtr<nsBaseContentList> mNameContentList;
 224   UniquePtr<nsTHashtable<ChangeCallbackEntry> > mChangeCallbacks;
 225   RefPtr<Element> mImageElement;
 226 };
 227
 228 }  // namespace mozilla
 229
 230 #endif  // #ifndef mozilla_IdentifierMapEntry_h