1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
|
/*
* 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 "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) : depth_(depth), leaf_(true) {
Build(text);
}
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() {
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::find_if(children_.begin(), children_.end(),
[key](const std::pair<int, Node*>& entry) {
return entry.first == key;
});
}
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_;
DISALLOW_COPY_AND_ASSIGN(Node);
};
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;
}
}
}
Node root_;
unsigned 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 leaf_;
DISALLOW_COPY_AND_ASSIGN(SuffixTree);
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_TEXT_SUFFIX_TREE_H_
|
