Changeset 102770 in webkit

Timestamp:

Dec 14, 2011 5:51:58 AM (12 years ago)

Author:

commit-queue@webkit.org

Message:

Add different salt to different types of selectors. So the CSS fast
path can tell the different between tags and class attributes with
otherwise identical values.
​https://bugs.webkit.org/show_bug.cgi?id=74284

Patch by Allan Sandfeld Jensen <​allan.jensen@nokia.com> on 2011-12-14
Reviewed by Antti Koivisto.

• css/SelectorChecker.cpp:

(WebCore::collectElementIdentifierHashes):
(WebCore::collectDescendantSelectorIdentifierHashes):

• css/SelectorChecker.h:

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• css/SelectorChecker.cpp (modified) (3 diffs)
• css/SelectorChecker.h (modified) (1 diff)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2011-12-14  Allan Sandfeld Jensen  <allan.jensen@nokia.com>
+
+        Add different salt to different types of selectors. So the CSS fast
+        path can tell the different between tags and class attributes with
+        otherwise identical values.
+        https://bugs.webkit.org/show_bug.cgi?id=74284
+
+        Reviewed by Antti Koivisto.
+
+        * css/SelectorChecker.cpp:
+        (WebCore::collectElementIdentifierHashes):
+        (WebCore::collectDescendantSelectorIdentifierHashes):
+        * css/SelectorChecker.h:
+
 2011-12-14  Pierre Rossi  <pierre.rossi@gmail.com>
 

trunk/Source/WebCore/css/SelectorChecker.cpp

@@ -79 +79 @@
 }
 
+// Salt to separate otherwise identical string hashes so a class-selector like .article won't match <article> elements.
+enum { TagNameSalt = 13, IdAttributeSalt = 17, ClassAttributeSalt = 19 };
+
 static inline void collectElementIdentifierHashes(const Element* element, Vector<unsigned, 4>& identifierHashes)
 {
-    identifierHashes.append(element->localName().impl()->existingHash());
+    identifierHashes.append(element->localName().impl()->existingHash() * TagNameSalt);
     if (element->hasID())
-        identifierHashes.append(element->idForStyleResolution().impl()->existingHash());
+        identifierHashes.append(element->idForStyleResolution().impl()->existingHash() * IdAttributeSalt);
     const StyledElement* styledElement = element->isStyledElement() ? static_cast<const StyledElement*>(element) : 0;
     if (styledElement && styledElement->hasClass()) {
@@ -89 +92 @@
         size_t count = classNames.size();
         for (size_t i = 0; i < count; ++i)
-            identifierHashes.append(classNames[i].impl()->existingHash());
+            identifierHashes.append(classNames[i].impl()->existingHash() * ClassAttributeSalt);
     }
 }
@@ -163 +166 @@
 static inline void collectDescendantSelectorIdentifierHashes(const CSSSelector* selector, unsigned*& hash, const unsigned* end)
 {
-    if ((selector->m_match == CSSSelector::Id || selector->m_match == CSSSelector::Class) && !selector->value().isEmpty())
-        (*hash++) = selector->value().impl()->existingHash();
+    switch (selector->m_match) {
+    case CSSSelector::Id:
+        if (!selector->value().isEmpty())
+            (*hash++) = selector->value().impl()->existingHash() * IdAttributeSalt;
+        break;
+    case CSSSelector::Class:
+        if (!selector->value().isEmpty())
+            (*hash++) = selector->value().impl()->existingHash() * ClassAttributeSalt;
+        break;
+    default:
+        break;
+    }
     if (hash == end)
         return;
     const AtomicString& localName = selector->tag().localName();
     if (localName != starAtom)
-        (*hash++) = localName.impl()->existingHash();
+        (*hash++) = localName.impl()->existingHash() * TagNameSalt;
 }
 

trunk/Source/WebCore/css/SelectorChecker.h

@@ -119 +119 @@
     };
     Vector<ParentStackFrame> m_parentStack;
-
+    
     // With 100 unique strings in the filter, 2^12 slot table has false positive rate of ~0.2%.
     static const unsigned bloomFilterKeyBits = 12;