BRBloomFilter.h

//
//  BRBloomFilter.h
//
//  Created by Aaron Voisine on 9/2/15.
//  Copyright (c) 2015 breadwallet LLC.
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in
//  all copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
//  THE SOFTWARE.

#ifndef BRBloomFilter_h
#define BRBloomFilter_h

#include <stddef.h>
#include <inttypes.h>

#ifdef __cplusplus
extern "C" {
#endif

// bloom filters are explained in BIP37: https://github.com/bitcoin/bips/blob/master/bip-0037.mediawiki

#define BLOOM_DEFAULT_FALSEPOSITIVE_RATE 0.0005 // use 0.00005 for less data, 0.001 for good anonymity
#define BLOOM_REDUCED_FALSEPOSITIVE_RATE 0.00005
#define BLOOM_UPDATE_NONE                0
#define BLOOM_UPDATE_ALL                 1
#define BLOOM_UPDATE_P2PUBKEY_ONLY       2
#define BLOOM_MAX_FILTER_LENGTH          36000 // this allows for 10,000 elements with a <0.0001% false positive rate

typedef struct {
    uint8_t *filter;
    size_t length;
    uint32_t hashFuncs;
    size_t elemCount;
    uint32_t tweak;
    uint8_t flags;
} BRBloomFilter;

// a bloom filter that matches everything is useful if a full node wants to use the filtered block protocol, which
// doesn't send transactions with blocks if the receiving node already received the tx prior to its inclusion in the
// block, allowing a full node to operate while using about half the network traffic
#define BR_BLOOM_FILTER_FULL ((BRBloomFilter) { &((struct { uint8_t u; }) { 0xff }).u, 1, 0, 0, 0, BLOOM_UPDATE_NONE })

// returns a newly allocated bloom filter struct that must be freed by calling BRBloomFilterFree()
BRBloomFilter *BRBloomFilterNew(double falsePositiveRate, size_t elemCount, uint32_t tweak, uint8_t flags);

// buf must contain a serialized filter
// returns a bloom filter struct that must be freed by calling BRBloomFilterFree()
BRBloomFilter *BRBloomFilterParse(const uint8_t *buf, size_t bufLen);

// returns number of bytes written to buf, or total bufLen needed if buf is NULL
size_t BRBloomFilterSerialize(const BRBloomFilter *filter, uint8_t *buf, size_t bufLen);

// true if data is matched by filter
int BRBloomFilterContainsData(const BRBloomFilter *filter, const uint8_t *data, size_t dataLen);

// add data to filter
void BRBloomFilterInsertData(BRBloomFilter *filter, const uint8_t *data, size_t dataLen);

// frees memory allocated for filter
void BRBloomFilterFree(BRBloomFilter *filter);

#ifdef __cplusplus
}
#endif

#endif // BRBloomFilter_h