Avoid constructing a DocumentFragment unnecessarily in DOMParser::par…

…seFromString() https://bugs.webkit.org/show_bug.cgi?id=260665 Reviewed by Yusuke Suzuki. Avoid constructing a DocumentFragment unnecessarily in DOMParser::parseFromString(). Have the HTML fast parser construct the subtree under the <body> element directly instead. * Source/WebCore/dom/DocumentFragment.cpp: (WebCore::DocumentFragment::parseHTML): * Source/WebCore/html/parser/HTMLDocumentParserFastPath.cpp: (WebCore::HTMLFastPathParser::HTMLFastPathParser): (WebCore::HTMLFastPathParser::parseCompleteInput): (WebCore::tryFastParsingHTMLFragmentImpl): (WebCore::tryFastParsingHTMLFragment): * Source/WebCore/html/parser/HTMLDocumentParserFastPath.h: * Source/WebCore/xml/DOMParser.cpp: (WebCore::DOMParser::parseFromString): Canonical link: https://commits.webkit.org/267242@main
WebKit · Aug 24, 2023 · 903209c · 903209c
1 parent d4d875b
commit 903209c
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Showing 4 changed files with 16 additions and 22 deletions.
diff --git a/Source/WebCore/dom/DocumentFragment.cpp b/Source/WebCore/dom/DocumentFragment.cpp
@@ -95,7 +95,9 @@ void DocumentFragment::parseHTML(const String& source, Element& contextElement,
         ASSERT(serializeFragment(*this, SerializedNodes::SubtreesOfChildren) == serializeFragment(referenceFragment, SerializedNodes::SubtreesOfChildren));
 #endif
         return;
-    }
+    } else if (hasChildNodes())
+        removeChildren();
+
     HTMLDocumentParser::parseDocumentFragment(source, *this, contextElement, parserContentPolicy);
 }
 

diff --git a/Source/WebCore/html/parser/HTMLDocumentParserFastPath.cpp b/Source/WebCore/html/parser/HTMLDocumentParserFastPath.cpp
@@ -33,7 +33,6 @@
 #include "HTMLDocumentParserFastPath.h"
 
 #include "Document.h"
-#include "DocumentFragment.h"
 #include "ElementAncestorIteratorInlines.h"
 #include "ElementTraversal.h"
 #include "FragmentScriptingPermission.h"
@@ -193,9 +192,9 @@ class HTMLFastPathParser {
     static_assert(std::is_same_v<CharacterType, UChar> || std::is_same_v<CharacterType, LChar>);
 
 public:
-    HTMLFastPathParser(CharacterSpan source, Document& document, DocumentFragment& fragment)
+    HTMLFastPathParser(CharacterSpan source, Document& document, ContainerNode& destinationParent)
         : m_document(document)
-        , m_fragment(fragment)
+        , m_destinationParent(destinationParent)
         , m_parsingBuffer(source.data(), source.size())
     {
     }
@@ -229,7 +228,7 @@ class HTMLFastPathParser {
 
 private:
     Document& m_document;
-    DocumentFragment& m_fragment;
+    ContainerNode& m_destinationParent;
 
     StringParsingBuffer<CharacterType> m_parsingBuffer;
 
@@ -463,7 +462,7 @@ class HTMLFastPathParser {
 
     template<typename ParentTag> void parseCompleteInput()
     {
-        parseChildren<ParentTag>(m_fragment);
+        parseChildren<ParentTag>(m_destinationParent);
         if (m_parsingBuffer.hasCharactersRemaining())
             didFail(HTMLFastPathResult::FailedDidntReachEndOfInput);
     }
@@ -888,23 +887,20 @@ static bool canUseFastPath(Element& contextElement, OptionSet<ParserContentPolic
 }
 
 template<typename CharacterType>
-static bool tryFastParsingHTMLFragmentImpl(const std::span<const CharacterType>& source, Document& document, DocumentFragment& fragment, Element& contextElement)
+static bool tryFastParsingHTMLFragmentImpl(const std::span<const CharacterType>& source, Document& document, ContainerNode& destinationParent, Element& contextElement)
 {
-    HTMLFastPathParser parser { source, document, fragment };
-    bool success = parser.parse(contextElement);
-    if (!success && fragment.hasChildNodes())
-        fragment.removeChildren();
-    return success;
+    HTMLFastPathParser parser { source, document, destinationParent };
+    return parser.parse(contextElement);
 }
 
-bool tryFastParsingHTMLFragment(const String& source, Document& document, DocumentFragment& fragment, Element& contextElement, OptionSet<ParserContentPolicy> policy)
+bool tryFastParsingHTMLFragment(const String& source, Document& document, ContainerNode& destinationParent, Element& contextElement, OptionSet<ParserContentPolicy> policy)
 {
     if (!canUseFastPath(contextElement, policy))
         return false;
 
     if (source.is8Bit())
-        return tryFastParsingHTMLFragmentImpl(source.span8(), document, fragment, contextElement);
-    return tryFastParsingHTMLFragmentImpl(source.span16(), document, fragment, contextElement);
+        return tryFastParsingHTMLFragmentImpl(source.span8(), document, destinationParent, contextElement);
+    return tryFastParsingHTMLFragmentImpl(source.span16(), document, destinationParent, contextElement);
 }
 
 #undef FOR_EACH_SUPPORTED_TAG

diff --git a/Source/WebCore/html/parser/HTMLDocumentParserFastPath.h b/Source/WebCore/html/parser/HTMLDocumentParserFastPath.h
@@ -35,13 +35,13 @@
 
 namespace WebCore {
 
+class ContainerNode;
 class Document;
-class DocumentFragment;
 class Element;
 
 enum class ParserContentPolicy : uint8_t;
 
-WEBCORE_EXPORT bool tryFastParsingHTMLFragment(const String& source, Document&, DocumentFragment&, Element& contextElement, OptionSet<ParserContentPolicy>);
+WEBCORE_EXPORT bool tryFastParsingHTMLFragment(const String& source, Document&, ContainerNode&, Element& contextElement, OptionSet<ParserContentPolicy>);
 
 } // namespace WebCore
 
diff --git a/Source/WebCore/xml/DOMParser.cpp b/Source/WebCore/xml/DOMParser.cpp
@@ -59,18 +59,14 @@ ExceptionOr<Ref<Document>> DOMParser::parseFromString(const String& string, cons
     document->setParserContentPolicy(parsingOptions);
     bool usedFastPath = false;
     if (contentType == "text/html"_s) {
-        auto fragment = DocumentFragment::create(document);
         auto body = HTMLBodyElement::create(document);
-        usedFastPath = tryFastParsingHTMLFragment(string, document, fragment, body, parsingOptions);
+        usedFastPath = tryFastParsingHTMLFragment(string, document, body, body, parsingOptions);
         if (LIKELY(usedFastPath)) {
             auto html = HTMLHtmlElement::create(document);
             document->appendChild(html);
             auto head = HTMLHeadElement::create(document);
             html->appendChild(head);
             html->appendChild(body);
-            auto result = body->appendChild(fragment);
-            if (UNLIKELY(result.hasException()))
-                return result.releaseException();
         }
     }
     if (!usedFastPath)