/*=============================================================================
# Filename: BloomFilter.h
# Author: Bookug Lobert
# Mail: 1181955272@qq.com
# Last Modified: 2015-10-20 13:18
# Description: http://blog.csdn.net/hguisu/article/details/7866173
TODO:this strategy can be used in Join and KVstore-search/modify/remove, or the uppest level!
really better? appropiate if key num small but search too many!
=============================================================================*/

#ifndef _UTIL_BLOOMFILTER_H
#define _UTIL_BLOOMFILTER_H

#include "Util.h"

#define SETBIT(ch, n) ch[n/8] |= 1 << (7-n%8)
#define GETBIT(ch, n) (ch[n/8] & (1<<(7-n%8))) >> (7-n%8)

class BloomFilter
{
public:
    BloomFilter();
    BloomFilter(unsigned _num);    //num of all keys
    void addRecord(int _record);
	//NOTICE:we hope a Bstr-like struct here, for the length maybe very large
    void addRecord(const char* _record, unsigned _len);
    bool checkRecord(int _record) const;
    bool checkRecord(const char* _record, unsigned _len) const;
	~BloomFilter();
private:
	unsigned length;		//length of total bits, mod 8 == 0
	char *filter;			//the bit space
	unsigned hfnum;			//num of hash functions 
	double rate;			//false positive
	HashFunction* hfptr;    //hash functions pointer array

	void init();
};

#endif //_UTIL_BLOOMFILTER_H