DC++ Code

/*
 * Copyright (C) 2001-2025 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 3 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/>.
 */

#include "stdinc.h"
#include "HashBloom.h"

#include <cmath>

#include "MerkleTree.h"

namespace dcpp {

size_t HashBloom::get_k(size_t n, size_t h) {
	for(size_t k = TTHValue::BITS/h; k > 1; --k) {
		uint64_t m = get_m(n, k);
		if(m >> 24 == 0) {
			return k;
		}
	}
	return 1;
}

uint64_t HashBloom::get_m(size_t n, size_t k) {
	uint64_t m = (static_cast<uint64_t>(ceil(static_cast<double>(n) * k / log(2.))));
	// 64-bit boundary as per spec
	return ((m + 63ULL) / 64ULL) * 64ULL;
}

void HashBloom::add(const TTHValue& tth) {
	for(size_t i = 0; i < k; ++i) {
		bloom[pos(tth, i)] = true;
	}
}

bool HashBloom::match(const TTHValue& tth) const {
	if(bloom.empty()) {
		return false;
	}
	for(size_t i = 0; i < k; ++i) {
		if(!bloom[pos(tth, i)]) {
			return false;
		}
	}
	return true;
}

void HashBloom::push_back(bool v) {
	bloom.push_back(v);
}

void HashBloom::reset(size_t k_, size_t m, size_t h_) {
	bloom.resize(m);
	k = k_;
	h = h_;
}

size_t HashBloom::pos(const TTHValue& tth, size_t n) const {
	if((n+1)*h > TTHValue::BITS) {
		return 0;
	}

	uint64_t x = 0;

	size_t start = n * h;
	for(size_t i = 0; i < h; ++i) {
		size_t bit = start + i;
		size_t byte = bit / 8;
		size_t pos = bit % 8;

		if(tth.data[byte] & (1 << pos)) {
			x |= (1LL << i);
		}
	}
	return x % bloom.size();
}

void HashBloom::copy_to(ByteVector& v) const {
	v.resize(bloom.size() / 8);
	for(size_t i = 0; i < bloom.size(); ++i) {
		v[i/8] |= bloom[i] << (i % 8);
	}
}

}