CSS Custom Properties (Variables)

third_party/WebKit/Source/core/css/CSSVariableData.h

+// Copyright 2015 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.
+
+#ifndef CSSVariableData_h
+#define CSSVariableData_h
+
+#include "core/css/parser/CSSParserToken.h"
+#include "core/css/parser/CSSParserTokenRange.h"
+#include "wtf/RefCounted.h"
+#include "wtf/text/WTFString.h"
+
+namespace blink {
+
+class CSSParserTokenRange;
+
+class CSSVariableData : public RefCounted<CSSVariableData> {
+    WTF_MAKE_NONCOPYABLE(CSSVariableData);
+    WTF_MAKE_FAST_ALLOCATED(CSSVariableData);
+public:
+    static PassRefPtr<CSSVariableData> create(const CSSParserTokenRange& range, bool needsVariableResolution = true)
+    {
+        return adoptRef(new CSSVariableData(range, needsVariableResolution));
+    }
+
+    static PassRefPtr<CSSVariableData> createResolved(const Vector<CSSParserToken>& resolvedTokens)
+    {
+        return adoptRef(new CSSVariableData(resolvedTokens));
+    }
+
+    CSSParserTokenRange tokenRange() { return m_tokens; }
+
+    const Vector<CSSParserToken>& tokens() { return m_tokens; }
+
+    bool needsVariableResolution() const { return m_needsVariableResolution; }
+private:
+    CSSVariableData(const CSSParserTokenRange&, bool needsVariableResolution);
+    CSSVariableData(const Vector<CSSParserToken>& resolvedTokens)

[alancutter (OOO until 2018), 2015/10/28 07:31:20]

What guarantees do we have that the backing strings for the resolved tokens will
outlive this CSSVariableData object?

Should we be passing in and storing a HashSet<String> of backing strings to
ensure we never access deallocated memory? Alternatively we could store the
backing strings on the ComputedStyle object to avoid having a HashSet per custom
property. At the very least we should have a comment describing why it's okay
for us to copy tokens with raw pointers in them.

[leviw_travelin_and_unemployed, 2015/10/30 21:41:16]

I added a comment about why its safe, and added an assert to
CSSVariableResolver.cpp

+        : m_tokens(resolvedTokens)
+        , m_needsVariableResolution(false)
+    { }
+
+    void consumeAndUpdateTokens(const CSSParserTokenRange&);
+    template<typename CharacterType> void updateTokens(const CSSParserTokenRange&);
+
+    String m_backingString;
+    Vector<CSSParserToken> m_tokens;
+    const bool m_needsVariableResolution;
+};
+
+} // namespace blink
+
+#endif // CSSVariableData_h