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
|
/*
* Copyright (C) 2001-2019 Jacek Sieka, arnetheduck on gmail point com
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#pragma once
#include <string.h>
#include "Text.h"
namespace dcpp {
/**
* A class that implements a fast substring search algo suited for matching
* one pattern against many strings (currently Quick Search, a variant of
* Boyer-Moore. Code based on "A very fast substring search algorithm" by
* D. Sunday).
* @todo Perhaps find an algo suitable for matching multiple substrings.
*/
class StringSearch {
public:
typedef vector<StringSearch> List;
StringSearch() { }
StringSearch(const string& aPattern) noexcept : pattern(Text::toLower(aPattern)) {
initDelta1();
}
StringSearch(const StringSearch& rhs) noexcept : pattern(rhs.pattern) {
memcpy(delta1, rhs.delta1, sizeof(delta1));
}
StringSearch& operator=(const StringSearch& rhs) {
memcpy(delta1, rhs.delta1, sizeof(delta1));
pattern = rhs.pattern;
return *this;
}
StringSearch& operator=(const string& rhs) {
pattern = Text::toLower(rhs);
initDelta1();
return *this;
}
bool operator==(const StringSearch& rhs) { return pattern == rhs.pattern; }
const string& getPattern() const { return pattern; }
/** Match a text against the pattern */
bool match(const string& aText) const noexcept {
// Lower-case representation of UTF-8 string, since we no longer have that 1 char = 1 byte...
string lower;
Text::toLower(aText, lower);
// uint8_t to avoid problems with signed char pointer arithmetic
uint8_t *tx = (uint8_t*)lower.c_str();
uint8_t *px = (uint8_t*)pattern.c_str();
string::size_type plen = pattern.length();
if(aText.length() < plen) {
return false;
}
uint8_t *end = tx + aText.length() - plen + 1;
while(tx < end) {
size_t i = 0;
for(; px[i] && (px[i] == tx[i]); ++i)
; // Empty!
if(px[i] == 0)
return true;
tx += delta1[tx[plen]];
}
return false;
}
private:
enum { ASIZE = 256 };
/**
* Delta1 shift, uint16_t because we expect all patterns to be shorter than 2^16
* chars.
*/
uint16_t delta1[ASIZE];
string pattern;
void initDelta1() {
uint16_t x = (uint16_t)(pattern.length() + 1);
uint16_t i;
for(i = 0; i < ASIZE; ++i) {
delta1[i] = x;
}
// x = pattern.length();
x--;
uint8_t* p = (uint8_t*)pattern.data();
for(i = 0; i < x; ++i) {
delta1[p[i]] = (uint16_t)(x - i);
}
}
};
} // namespace dcpp
|
