Introduce StringImpl::createPreallocatedStatic

third_party/WebKit/Source/wtf/text/StringStatics.cpp

Index: third_party/WebKit/Source/wtf/text/StringStatics.cpp
diff --git a/third_party/WebKit/Source/wtf/text/StringStatics.cpp b/third_party/WebKit/Source/wtf/text/StringStatics.cpp
index 7a807f6aa21917383201f0813aef5c58581958d2..27317556db776550f21882575dd6faef06349968 100644
--- a/third_party/WebKit/Source/wtf/text/StringStatics.cpp
+++ b/third_party/WebKit/Source/wtf/text/StringStatics.cpp
@@ -79,24 +79,44 @@ void AtomicString::init()
     new (NotNull, (void*)&emptyAtom) AtomicString("");
 }
 
+template <unsigned charactersCount>
+struct PreallocatedStringImplStorage {
+    // A StringImpl is built at stringImplStorage in-place.
+    // |characters| must be placed soon after |stringImplStorage| to match the memory layout requirement of StringImpl.
+    char stringImplStorage[sizeof(StringImpl)];
+    char characters[charactersCount];
+};
+
 template<unsigned charactersCount>
-PassRefPtr<StringImpl> addStaticASCIILiteral(const char (&characters)[charactersCount])
+PassRefPtr<StringImpl> addStaticASCIILiteral(PreallocatedStringImplStorage<charactersCount>& storage)
 {
+    ASSERT(reinterpret_cast<char*>(reinterpret_cast<StringImpl*>(&storage) + 1) == storage.characters);
     unsigned length = charactersCount - 1;
-    unsigned hash = StringHasher::computeHashAndMaskTop8Bits(reinterpret_cast<const LChar*>(characters), length);
-    return adoptRef(StringImpl::createStatic(characters, length, hash));
+    unsigned hash = StringHasher::computeHashAndMaskTop8Bits(reinterpret_cast<const LChar*>(storage.characters), length);
+    return adoptRef(StringImpl::createPreallocatedStatic(&storage, length, hash));
 }
 
 void StringStatics::init()
 {
     ASSERT(isMainThread());
 
+#define ALLOCATE_STRING_IMPL_STORAGE_FOR_LITERAL(name, literal)  \
+    static PreallocatedStringImplStorage<sizeof(literal)> name = {{}, literal}
+
+    ALLOCATE_STRING_IMPL_STORAGE_FOR_LITERAL(star, "*");
+    ALLOCATE_STRING_IMPL_STORAGE_FOR_LITERAL(xml, "xml");
+    ALLOCATE_STRING_IMPL_STORAGE_FOR_LITERAL(xmlns, "xmlns");
+    ALLOCATE_STRING_IMPL_STORAGE_FOR_LITERAL(xlink, "xlink");
+    ALLOCATE_STRING_IMPL_STORAGE_FOR_LITERAL(xmlnsWithColon, "xmlns:");
+
+#undef ALLOCATE_STRING_IMPL_STORAGE_FOR_LITERAL
+
     // FIXME: These should be allocated at compile time.
-    new (NotNull, (void*)&starAtom) AtomicString("*", AtomicString::ConstructFromLiteral);
-    new (NotNull, (void*)&xmlAtom) AtomicString(addStaticASCIILiteral("xml"));
-    new (NotNull, (void*)&xmlnsAtom) AtomicString(addStaticASCIILiteral("xmlns"));
-    new (NotNull, (void*)&xlinkAtom) AtomicString(addStaticASCIILiteral("xlink"));
-    new (NotNull, (void*)&xmlnsWithColon) String("xmlns:");
+    new (NotNull, (void*)&starAtom) AtomicString(addStaticASCIILiteral(star));
+    new (NotNull, (void*)&xmlAtom) AtomicString(addStaticASCIILiteral(xml));
+    new (NotNull, (void*)&xmlnsAtom) AtomicString(addStaticASCIILiteral(xmlns));
+    new (NotNull, (void*)&xlinkAtom) AtomicString(addStaticASCIILiteral(xlink));
+    new (NotNull, (void*)&xlinkAtom) AtomicString(addStaticASCIILiteral(xmlnsWithColon));
 }
 
 }