1/*
2 * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
3 *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
4 * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
5 * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
6 * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
7 * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
8 * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
9 * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
10 * Copyright (C) Research In Motion Limited 2011. All rights reserved.
11 * Copyright (C) 2012 Google Inc. All rights reserved.
12 *
13 * This library is free software; you can redistribute it and/or
14 * modify it under the terms of the GNU Library General Public
15 * License as published by the Free Software Foundation; either
16 * version 2 of the License, or (at your option) any later version.
17 *
18 * This library is distributed in the hope that it will be useful,
19 * but WITHOUT ANY WARRANTY; without even the implied warranty of
20 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
21 * Library General Public License for more details.
22 *
23 * You should have received a copy of the GNU Library General Public License
24 * along with this library; see the file COPYING.LIB.  If not, write to
25 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
26 * Boston, MA 02110-1301, USA.
27 */
28
29#ifndef SelectorFilter_h
30#define SelectorFilter_h
31
32#include "core/dom/Element.h"
33#include "wtf/BloomFilter.h"
34#include "wtf/Vector.h"
35
36namespace blink {
37
38class CSSSelector;
39
40class SelectorFilter {
41    DISALLOW_ALLOCATION();
42public:
43    class ParentStackFrame {
44        ALLOW_ONLY_INLINE_ALLOCATION();
45    public:
46        ParentStackFrame() : element(nullptr) { }
47        explicit ParentStackFrame(Element& element) : element(&element) { }
48
49        void trace(Visitor*);
50
51        RawPtrWillBeMember<Element> element;
52        Vector<unsigned, 4> identifierHashes;
53    };
54
55    void pushParentStackFrame(Element& parent);
56    void popParentStackFrame();
57
58    void setupParentStack(Element& parent);
59    void pushParent(Element& parent);
60    void popParent() { popParentStackFrame(); }
61    bool parentStackIsEmpty() const { return m_parentStack.isEmpty(); }
62    bool parentStackIsConsistent(const ContainerNode* parentNode) const { return !m_parentStack.isEmpty() && m_parentStack.last().element == parentNode; }
63
64    template <unsigned maximumIdentifierCount>
65    inline bool fastRejectSelector(const unsigned* identifierHashes) const;
66    static void collectIdentifierHashes(const CSSSelector&, unsigned* identifierHashes, unsigned maximumIdentifierCount);
67
68    void trace(Visitor*);
69
70private:
71    WillBeHeapVector<ParentStackFrame> m_parentStack;
72
73    // With 100 unique strings in the filter, 2^12 slot table has false positive rate of ~0.2%.
74    static const unsigned bloomFilterKeyBits = 12;
75    OwnPtr<BloomFilter<bloomFilterKeyBits> > m_ancestorIdentifierFilter;
76};
77
78template <unsigned maximumIdentifierCount>
79inline bool SelectorFilter::fastRejectSelector(const unsigned* identifierHashes) const
80{
81    ASSERT(m_ancestorIdentifierFilter);
82    for (unsigned n = 0; n < maximumIdentifierCount && identifierHashes[n]; ++n) {
83        if (!m_ancestorIdentifierFilter->mayContain(identifierHashes[n]))
84            return true;
85    }
86    return false;
87}
88
89}
90
91WTF_ALLOW_INIT_WITH_MEM_FUNCTIONS(blink::SelectorFilter::ParentStackFrame);
92
93#endif
94