Bug 834877 part 4. Add overloads of GetAttr() and GetId() that take a DOMString. r=peterv

content/base/public/Element.h

@@ -45,6 +45,8 @@
 #include "nsISMILAttr.h"
 #include "nsClientRect.h"
 #include "nsEvent.h"
+#include "nsAttrValue.h"
+#include "mozilla/dom/BindingDeclarations.h"
 
 class nsIDOMEventListener;
 class nsIFrame;
@@ -461,7 +463,7 @@ public:
   nsresult SetParsedAttr(int32_t aNameSpaceID, nsIAtom* aName, nsIAtom* aPrefix,
                          nsAttrValue& aParsedValue, bool aNotify);
   virtual bool GetAttr(int32_t aNameSpaceID, nsIAtom* aName,
-                         nsAString& aResult) const;
+                       nsAString& aResult) const;
   virtual bool HasAttr(int32_t aNameSpaceID, nsIAtom* aName) const;
   // aCaseSensitive == eIgnoreCaase means ASCII case-insensitive matching.
   virtual bool AttrValueIs(int32_t aNameSpaceID, nsIAtom* aName,
@@ -517,6 +519,23 @@ private:
                           const MappedAttributeEntry* const aMaps[],
                           uint32_t aMapCount);
 
+protected:
+  inline bool GetAttr(int32_t aNameSpaceID, nsIAtom* aName,
+                      mozilla::dom::DOMString& aResult) const
+  {
+    NS_ASSERTION(nullptr != aName, "must have attribute name");
+    NS_ASSERTION(aNameSpaceID != kNameSpaceID_Unknown,
+                 "must have a real namespace ID!");
+    MOZ_ASSERT(aResult.HasStringBuffer() && aResult.StringBufferLength() == 0,
+               "Should have empty string coming in");
+    const nsAttrValue* val = mAttrsAndChildren.GetAttr(aName, aNameSpaceID);
+    if (val) {
+      val->ToString(aResult);
+    }
+    // else DOMString comes pre-emptied.
+    return val != nullptr;
+  }
+
 public:
   void GetTagName(nsAString& aTagName) const
   {
@@ -526,6 +545,10 @@ public:
   {
     GetAttr(kNameSpaceID_None, nsGkAtoms::id, aId);
   }
+  void GetId(mozilla::dom::DOMString& aId) const
+  {
+    GetAttr(kNameSpaceID_None, nsGkAtoms::id, aId);
+  }
   void SetId(const nsAString& aId)
   {
     SetAttr(kNameSpaceID_None, nsGkAtoms::id, aId, true);

content/base/src/Element.cpp

@@ -1961,23 +1961,10 @@ bool
 Element::GetAttr(int32_t aNameSpaceID, nsIAtom* aName,
                  nsAString& aResult) const
 {
-  NS_ASSERTION(nullptr != aName, "must have attribute name");
-  NS_ASSERTION(aNameSpaceID != kNameSpaceID_Unknown,
-               "must have a real namespace ID!");
-
-  const nsAttrValue* val = mAttrsAndChildren.GetAttr(aName, aNameSpaceID);
-  if (!val) {
-    // Since we are returning a success code we'd better do
-    // something about the out parameters (someone may have
-    // given us a non-empty string).
-    aResult.Truncate();
-    
-    return false;
-  }
-
-  val->ToString(aResult);
-
-  return true;
+  DOMString str;
+  bool haveAttr = GetAttr(aNameSpaceID, aName, str);
+  str.ToString(aResult);
+  return haveAttr;
 }
 
 bool

content/base/src/nsAttrValue.h

@@ -20,9 +20,10 @@
 #include "nsCOMPtr.h"
 #include "SVGAttrValueWrapper.h"
 #include "nsTArrayForwardDeclare.h"
+#include "nsIAtom.h"
+#include "mozilla/dom/BindingDeclarations.h"
 
 class nsAString;
-class nsIAtom;
 class nsIDocument;
 class nsStyledElementNotElementCSSInlineStyle;
 struct MiscContainer;
@@ -159,6 +160,8 @@ public:
   void SwapValueWith(nsAttrValue& aOther);
 
   void ToString(nsAString& aResult) const;
+  inline void ToString(mozilla::dom::DOMString& aResult) const;
+
   /**
    * Returns the value of this object as an atom. If necessary, the value will
    * first be serialised using ToString before converting to an atom.
@@ -464,4 +467,30 @@ nsAttrValue::IsEmptyString() const
   return !mBits;
 }
 
+inline void
+nsAttrValue::ToString(mozilla::dom::DOMString& aResult) const
+{
+  switch (Type()) {
+    case eString:
+    {
+      nsStringBuffer* str = static_cast<nsStringBuffer*>(GetPtr());
+      if (str) {
+        aResult.SetStringBuffer(str, str->StorageSize()/sizeof(PRUnichar) - 1);
+      }
+      // else aResult is already empty
+      return;
+    }
+    case eAtom:
+    {
+      nsIAtom *atom = static_cast<nsIAtom*>(GetPtr());
+      aResult.SetStringBuffer(atom->GetStringBuffer(), atom->GetLength());
+      break;
+    }
+    default:
+    {
+      ToString(aResult.AsAString());
+    }
+  }
+}
+
 #endif

xpcom/ds/nsIAtom.idl

@@ -40,15 +40,15 @@ interface nsIAtom : nsISupports
 
 %{C++
   // note this is NOT virtual so this won't muck with the vtable!
-  inline bool Equals(const nsAString& aString) {
+  inline bool Equals(const nsAString& aString) const {
     return aString.Equals(nsDependentString(mString, mLength));
   }
 
-  inline const PRUnichar* GetUTF16String() {
+  inline const PRUnichar* GetUTF16String() const {
     return mString;
   }
 
-  inline const uint32_t GetLength() {
+  inline const uint32_t GetLength() const {
     return mLength;
   }
 
@@ -56,6 +56,10 @@ interface nsIAtom : nsISupports
     nsStringBuffer::FromData(mString)->ToString(mLength, aBuf);
   }
 
+  inline nsStringBuffer* GetStringBuffer() const {
+    return nsStringBuffer::FromData(mString);
+  }
+
   /**
    * A hashcode that is better distributed than the actual atom
    * pointer, for use in situations that need a well-distributed