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133 lines
3.0 KiB
133 lines
3.0 KiB
/* |
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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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/** |
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* Construct an empty filter |
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*/ |
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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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* Construct from a raw filter |
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* |
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* @param b Raw filter bits, must be exactly bytes() in length, or NULL to construct empty |
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*/ |
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BloomFilter(const void *b) |
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throw() |
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{ |
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if (b) |
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memcpy(_field,b,sizeof(_field)); |
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else 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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static inline unsigned int bits() 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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static inline unsigned int bytes() 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 set(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))) != 0); |
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} |
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/** |
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* Clear a random bit in this bloom filter |
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* |
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* @param rn Random number |
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*/ |
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inline void decay(unsigned int rn) |
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throw() |
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{ |
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_field[(rn >> 3) % (B / 8)] &= ~((unsigned char)(1 << (rn & 7))); |
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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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