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/*
* Copyright (C) 2010 Adam Barth. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include <wtf/TZoneMallocInlines.h>
#include <wtf/Vector.h>
#include <wtf/text/WTFString.h>
namespace WebCore {
class UnicodeCodebook {
public:
static int codeWord(UChar c) { return c; }
enum { codeSize = 1 << 8 * sizeof(UChar) };
};
class ASCIICodebook {
public:
static int codeWord(UChar c) { return c & (codeSize - 1); }
enum { codeSize = 1 << (8 * sizeof(char) - 1) };
};
template<typename Codebook>
class SuffixTree {
WTF_MAKE_TZONE_ALLOCATED_INLINE(SuffixTree);
WTF_MAKE_NONCOPYABLE(SuffixTree)
public:
SuffixTree(const String& text, unsigned depth)
: m_depth(depth)
, m_leaf(true)
{
build(text);
}
bool mightContain(const String& query)
{
Node* current = &m_root;
int limit = std::min(m_depth, query.length());
for (int i = 0; i < limit; ++i) {
auto it = current->find(Codebook::codeWord(query[i]));
if (it == current->end())
return false;
current = it->node;
}
return true;
}
private:
class Node {
WTF_MAKE_TZONE_ALLOCATED_INLINE(Node);
public:
Node(bool isLeaf = false)
: m_isLeaf(isLeaf)
{
}
~Node()
{
for (auto& entry : m_children) {
auto* child = entry.node;
if (child && !child->m_isLeaf)
delete child;
}
}
Node*& childAt(int codeWord);
auto find(int codeWord)
{
return std::find_if(m_children.begin(), m_children.end(), [codeWord](auto& entry) {
return entry.codeWord == codeWord;
});
}
auto end() { return m_children.end(); }
private:
struct ChildWithCodeWord {
int codeWord;
Node* node;
};
Vector<ChildWithCodeWord> m_children;
bool m_isLeaf;
};
void build(const String& text)
{
for (unsigned base = 0; base < text.length(); ++base) {
Node* current = &m_root;
unsigned limit = std::min(base + m_depth, text.length());
for (unsigned offset = 0; base + offset < limit; ++offset) {
ASSERT(current != &m_leaf);
Node*& child = current->childAt(Codebook::codeWord(text[base + offset]));
if (!child)
child = base + offset + 1 == limit ? &m_leaf : new Node();
current = child;
}
}
}
Node m_root;
unsigned m_depth;
// Instead of allocating a fresh empty leaf node for ever leaf in the tree
// (there can be a lot of these), we alias all the leaves to this "static"
// leaf node.
Node m_leaf;
};
template<typename Codebook>
inline auto SuffixTree<Codebook>::Node::childAt(int codeWord) -> Node*&
{
auto it = find(codeWord);
if (it != m_children.end())
return it->node;
m_children.append(ChildWithCodeWord { codeWord, nullptr });
return m_children.last().node;
}
} // namespace WebCore
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