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 "Element.h"
33#include <wtf/BloomFilter.h>
34#include <wtf/Vector.h>
35
36namespace WebCore {
37
38class CSSSelector;
39
40class SelectorFilter {
41public:
42    void pushParentStackFrame(Element* parent);
43    void popParentStackFrame();
44
45    void setupParentStack(Element* parent);
46    void pushParent(Element* parent);
47    void popParent() { popParentStackFrame(); }
48    bool parentStackIsEmpty() const { return m_parentStack.isEmpty(); }
49    bool parentStackIsConsistent(const ContainerNode* parentNode) const { return !m_parentStack.isEmpty() && m_parentStack.last().element == parentNode; }
50
51    template <unsigned maximumIdentifierCount>
52    inline bool fastRejectSelector(const unsigned* identifierHashes) const;
53    static void collectIdentifierHashes(const CSSSelector*, unsigned* identifierHashes, unsigned maximumIdentifierCount);
54
55private:
56    struct ParentStackFrame {
57        ParentStackFrame() : element(0) { }
58        ParentStackFrame(Element* element) : element(element) { }
59        Element* element;
60        Vector<unsigned, 4> identifierHashes;
61    };
62    Vector<ParentStackFrame> m_parentStack;
63
64    // With 100 unique strings in the filter, 2^12 slot table has false positive rate of ~0.2%.
65    static const unsigned bloomFilterKeyBits = 12;
66    OwnPtr<BloomFilter<bloomFilterKeyBits> > m_ancestorIdentifierFilter;
67};
68
69template <unsigned maximumIdentifierCount>
70inline bool SelectorFilter::fastRejectSelector(const unsigned* identifierHashes) const
71{
72    ASSERT(m_ancestorIdentifierFilter);
73    for (unsigned n = 0; n < maximumIdentifierCount && identifierHashes[n]; ++n) {
74        if (!m_ancestorIdentifierFilter->mayContain(identifierHashes[n]))
75            return true;
76    }
77    return false;
78}
79
80}
81
82#endif
83