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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 COMPUTER, 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.
*/
#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_TEXT_SUFFIX_TREE_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_TEXT_SUFFIX_TREE_H_
#include <algorithm>
#include <utility>
#include "base/check_op.h"
#include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
#include "third_party/blink/renderer/platform/wtf/text/wtf_string.h"
#include "third_party/blink/renderer/platform/wtf/vector.h"
namespace blink {
class UnicodeCodebook {
STATIC_ONLY(UnicodeCodebook);
public:
static int CodeWord(UChar c) { return c; }
enum { kCodeSize = 1 << 8 * sizeof(UChar) };
};
class ASCIICodebook {
STATIC_ONLY(ASCIICodebook);
public:
static int CodeWord(UChar c) { return c & (kCodeSize - 1); }
enum { kCodeSize = 1 << (8 * sizeof(char) - 1) };
};
template <typename Codebook>
class SuffixTree {
USING_FAST_MALLOC(SuffixTree);
public:
SuffixTree(const String& text, unsigned depth) : leaf_(true), depth_(depth) {
Build(text);
}
SuffixTree(const SuffixTree&) = delete;
SuffixTree& operator=(const SuffixTree&) = delete;
bool MightContain(const String& query) {
Node* current = &root_;
int limit = std::min(depth_, query.length());
for (int i = 0; i < limit; ++i) {
auto iter = current->Find(Codebook::CodeWord(query[i]));
if (iter == current->End())
return false;
current = iter->second;
}
return true;
}
private:
class Node {
USING_FAST_MALLOC(Node);
public:
Node(bool is_leaf = false) : is_leaf_(is_leaf) {}
Node(const Node&) = delete;
Node& operator=(const Node&) = delete;
~Node() {
for (const auto& pair : children_) {
Node* child = pair.second;
if (child && !child->is_leaf_)
delete child;
}
}
Node*& At(int key) {
auto it = Find(key);
if (it != children_.end())
return it->second;
children_.emplace_back(key, nullptr);
return children_.back().second;
}
typename Vector<std::pair<int, Node*>>::iterator Find(int key) {
return std::ranges::find(children_, key, &std::pair<int, Node*>::first);
}
typename Vector<std::pair<int, Node*>>::iterator End() {
return children_.end();
}
private:
// TODO(tsepez): convert to base::flat_map when allowed in blink.
Vector<std::pair<int, Node*>> children_;
const bool is_leaf_;
};
void Build(const String& text) {
for (unsigned base = 0; base < text.length(); ++base) {
Node* current = &root_;
unsigned limit = std::min(base + depth_, text.length());
for (unsigned offset = 0; base + offset < limit; ++offset) {
DCHECK_NE(current, &leaf_);
Node*& child = current->At(Codebook::CodeWord(text[base + offset]));
if (!child)
child = base + offset + 1 == limit ? &leaf_ : new Node();
current = child;
}
}
}
// 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 leaf_;
Node root_;
unsigned depth_;
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_TEXT_SUFFIX_TREE_H_
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