Lazy Parse CSS

third_party/WebKit/Source/core/css/parser/CSSTokenizer.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/css/parser/CSSTokenizer.h"
 
 namespace blink {
 #include "core/CSSTokenizerCodepoints.cpp"
 }
 
 #include "core/css/parser/CSSParserIdioms.h"
 #include "core/css/parser/CSSParserObserverWrapper.h"
 #include "core/css/parser/CSSParserTokenRange.h"
 #include "core/css/parser/CSSTokenizerInputStream.h"
 #include "core/html/parser/HTMLParserIdioms.h"
 #include "wtf/text/CharacterNames.h"
 
 namespace blink {
 
 CSSTokenizer::Scope::Scope(const String& string)
-: m_string(string)
+    : m_stringPool(new Vector<String>)

[Timothy Loh, 2016/09/26 05:18:01]

Let's lazily allocate this -- I don't think it'll be used frequently and this is
a non-trivial cost for parsing small bits of CSS (e.g. setting style.padding =
'10px 20px')

[Charlie Harrison, 2016/09/26 22:14:45]

Great point. Done.

+    , m_string(string)
 {
     // According to the spec, we should perform preprocessing here.
     // See: http://dev.w3.org/csswg/css-syntax/#input-preprocessing
     //
     // However, we can skip this step since:
     // * We're using HTML spaces (which accept \r and \f as a valid white space)
     // * Do not count white spaces
     // * CSSTokenizerInputStream::nextInputChar() replaces NULLs for replacement characters
 
     if (string.isEmpty())
         return;
 
     // To avoid resizing we err on the side of reserving too much space.
     // Most strings we tokenize have about 3.5 to 5 characters per token.
     m_tokens.reserveInitialCapacity(string.length() / 3);
 
     CSSTokenizerInputStream input(string);
     CSSTokenizer tokenizer(input, *this);
     while (true) {
         CSSParserToken token = tokenizer.nextToken();
         if (token.type() == CommentToken)
             continue;
         if (token.type() == EOFToken)
             return;
         m_tokens.append(token);
     }
 }
 
 CSSTokenizer::Scope::Scope(const String& string, CSSParserObserverWrapper& wrapper)
-: m_string(string)
+    : m_stringPool(new Vector<String>)
+    , m_string(string)
 {
     if (string.isEmpty())
         return;
 
     CSSTokenizerInputStream input(string);
     CSSTokenizer tokenizer(input, *this);
 
     unsigned offset = 0;
     while (true) {
         CSSParserToken token = tokenizer.nextToken();
@@ skipping 664 matching lines @@
     return areIdentifier;
 }
 
 StringView CSSTokenizer::registerString(const String& string)
 {
     m_scope.storeString(string);
     return string;
 }
 
 } // namespace blink