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/*
* 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 "typedefs.h"
namespace dcpp {
template<size_t N>
class BloomFilter {
public:
BloomFilter(size_t tableSize) { table.resize(tableSize); }
~BloomFilter() { }
void add(const string& s) {xadd(s, N); }
bool match(const StringList& s) const {
for(auto& i: s) {
if(!match(i))
return false;
}
return true;
}
bool match(const string& s) const {
if(s.length() >= N) {
string::size_type l = s.length() - N;
for(string::size_type i = 0; i <= l; ++i) {
if(!table[getPos(s, i, N)]) {
return false;
}
}
}
return true;
}
void clear() {
size_t s = table.size();
table.clear();
table.resize(s);
}
#ifdef TESTER
void print_table_status() {
int tot = 0;
for (unsigned int i = 0; i < table.size(); ++i) if (table[i] == true) ++tot;
std::cout << "table status: " << tot << " of " << table.size()
<< " filled, for an occupancy percentage of " << (100.*tot)/table.size()
<< "%" << std::endl;
}
#endif
private:
void xadd(const string& s, size_t n) {
if(s.length() >= n) {
string::size_type l = s.length() - n;
for(string::size_type i = 0; i <= l; ++i) {
table[getPos(s, i, n)] = true;
}
}
}
/* This is roughly how boost::hash does it */
size_t getPos(const string& s, size_t i, size_t l) const {
size_t h = 0;
const char* c = s.data() + i;
const char* end = s.data() + i + l;
for(; c < end; ++c) {
h ^= *c + 0x9e3779b9 + (h<<6) + (h>>2);
}
return (h % table.size());
}
vector<bool> table;
};
} // namespace dcpp
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