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/*
* ZeroTier One - Global Peer to Peer Ethernet
* Copyright (C) 2012-2013 ZeroTier Networks LLC
*
* 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 <http://www.gnu.org/licenses/>.
*
* --
*
* ZeroTier may be used and distributed under the terms of the GPLv3, which
* are available at: http://www.gnu.org/licenses/gpl-3.0.html
*
* If you would like to embed ZeroTier into a commercial application or
* redistribute it in a modified binary form, please contact ZeroTier Networks
* LLC. Start here: http://www.zerotier.com/
*/
#ifndef _ZT_BLOOMFILTER_HPP
#define _ZT_BLOOMFILTER_HPP
#include <string.h>
#include "Utils.hpp"
namespace ZeroTier {
/**
* A simple bit field bloom filter
*
* This actually isn't a total filter, in that it does not contain a hashing
* algorithm. It's up to the caller to hash/sum the items being remembered
* so that the distribution of 'n' is random across the filter's size range.
*
* @tparam B Size in BITS, must be a multiple of 8
*/
template<unsigned int B>
class BloomFilter
{
public:
/**
* Construct an empty filter
*/
BloomFilter()
throw()
{
memset(_field,0,sizeof(_field));
}
/**
* Construct from a raw filter
*
* @param b Raw filter bits, must be exactly bytes() in length, or NULL to construct empty
*/
BloomFilter(const void *b)
throw()
{
if (b)
memcpy(_field,b,sizeof(_field));
else memset(_field,0,sizeof(_field));
}
/**
* @return Size of filter in bits
*/
static inline unsigned int bits() throw() { return B; }
/**
* @return Size of filter in bytes
*/
static inline unsigned int bytes() throw() { return (B / 8); }
/**
* @return Pointer to portable array of bytes of bytes() length representing filter
*/
inline const unsigned char *data() const throw() { return _field; }
/**
* Clear all bits in filter
*/
inline void clear()
throw()
{
memset(_field,0,sizeof(_field));
}
/**
* @param n Value to set
*/
inline void set(unsigned int n)
throw()
{
n %= B;
_field[n / 8] |= (1 << (n % 8));
}
/**
* @param n Value to test
* @return True if value is present is set
*/
inline bool contains(unsigned int n)
throw()
{
n %= B;
return ((_field[n / 8] & (1 << (n % 8))) != 0);
}
/**
* Clear a random bit in this bloom filter
*
* @param rn Random number
*/
inline void decay(unsigned int rn)
throw()
{
_field[(rn >> 3) % (B / 8)] &= ~((unsigned char)(1 << (rn & 7)));
}
private:
unsigned char _field[B / 8];
};
} // namespace ZeroTier
#endif
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