mirror of
https://github.com/zerotier/ZeroTierOne.git
synced 2024-12-22 22:32:22 +00:00
124 lines
2.9 KiB
C++
124 lines
2.9 KiB
C++
/*
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* ZeroTier One - Global Peer to Peer Ethernet
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* Copyright (C) 2012-2013 ZeroTier Networks LLC
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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* --
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*
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* ZeroTier may be used and distributed under the terms of the GPLv3, which
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* are available at: http://www.gnu.org/licenses/gpl-3.0.html
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*
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* If you would like to embed ZeroTier into a commercial application or
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* redistribute it in a modified binary form, please contact ZeroTier Networks
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* LLC. Start here: http://www.zerotier.com/
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*/
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#ifndef _ZT_BLOOMFILTER_HPP
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#define _ZT_BLOOMFILTER_HPP
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#include <string.h>
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#include "Utils.hpp"
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namespace ZeroTier {
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/**
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* A simple bit field bloom filter
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*
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* This actually isn't a total filter, in that it does not contain a hashing
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* algorithm. It's up to the caller to hash/sum the items being remembered
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* so that the distribution of 'n' is random.
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*
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* @tparam B Size in BITS, must be a multiple of 8
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*/
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template<unsigned int B>
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class BloomFilter
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{
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public:
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BloomFilter()
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throw()
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{
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memset(_field,0,sizeof(_field));
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}
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/**
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* @return Size of filter in bits
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*/
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inline unsigned int bits() const throw() { return B; }
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/**
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* @return Size of filter in bytes
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*/
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inline unsigned int bytes() const throw() { return (B / 8); }
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/**
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* @return Pointer to portable array of bytes of bytes() length representing filter
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*/
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inline const unsigned char *data() const throw() { return _field; }
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/**
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* Clear all bits in filter
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*/
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inline void clear()
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throw()
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{
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memset(_field,0,sizeof(_field));
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}
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/**
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* @param n Value to set
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*/
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inline void add(unsigned int n)
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throw()
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{
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n %= B;
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_field[n / 8] |= (1 << (n % 8));
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}
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/**
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* @param n Value to test
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* @return True if value is present is set
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*/
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inline bool contains(unsigned int n)
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throw()
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{
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n %= B;
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return (_field[n / 8] & (1 << (n % 8)));
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}
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/**
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* Clear one or more random bits
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*
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* This is used to apply probabilistic decay and hence "fuzziness" to
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* a bloom filter over time.
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*
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* @param bits Number of bits to clear
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*/
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inline void decay(unsigned int bits)
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throw()
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{
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for(unsigned int i=0;i<bits;++i) {
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unsigned int rn = Utils::randomInt<unsigned int>();
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_field[(rn >> 7) % (B / 8)] &= ~((unsigned char)(1 << (rn & 7)));
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}
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}
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private:
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unsigned char _field[B / 8];
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};
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} // namespace ZeroTier
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#endif
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