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Diffstat (limited to 'src/blockfilter.h')
-rw-r--r-- | src/blockfilter.h | 145 |
1 files changed, 145 insertions, 0 deletions
diff --git a/src/blockfilter.h b/src/blockfilter.h new file mode 100644 index 0000000000..46833ac0be --- /dev/null +++ b/src/blockfilter.h @@ -0,0 +1,145 @@ +// Copyright (c) 2018 The Bitcoin Core developers +// Distributed under the MIT software license, see the accompanying +// file COPYING or http://www.opensource.org/licenses/mit-license.php. + +#ifndef BITCOIN_BLOCKFILTER_H +#define BITCOIN_BLOCKFILTER_H + +#include <set> +#include <stdint.h> +#include <vector> + +#include <primitives/block.h> +#include <serialize.h> +#include <uint256.h> +#include <undo.h> + +/** + * This implements a Golomb-coded set as defined in BIP 158. It is a + * compact, probabilistic data structure for testing set membership. + */ +class GCSFilter +{ +public: + typedef std::vector<unsigned char> Element; + typedef std::set<Element> ElementSet; + +private: + uint64_t m_siphash_k0; + uint64_t m_siphash_k1; + uint8_t m_P; //!< Golomb-Rice coding parameter + uint32_t m_M; //!< Inverse false positive rate + uint32_t m_N; //!< Number of elements in the filter + uint64_t m_F; //!< Range of element hashes, F = N * M + std::vector<unsigned char> m_encoded; + + /** Hash a data element to an integer in the range [0, N * M). */ + uint64_t HashToRange(const Element& element) const; + + std::vector<uint64_t> BuildHashedSet(const ElementSet& elements) const; + + /** Helper method used to implement Match and MatchAny */ + bool MatchInternal(const uint64_t* sorted_element_hashes, size_t size) const; + +public: + + /** Constructs an empty filter. */ + GCSFilter(uint64_t siphash_k0 = 0, uint64_t siphash_k1 = 0, uint8_t P = 0, uint32_t M = 0); + + /** Reconstructs an already-created filter from an encoding. */ + GCSFilter(uint64_t siphash_k0, uint64_t siphash_k1, uint8_t P, uint32_t M, + std::vector<unsigned char> encoded_filter); + + /** Builds a new filter from the params and set of elements. */ + GCSFilter(uint64_t siphash_k0, uint64_t siphash_k1, uint8_t P, uint32_t M, + const ElementSet& elements); + + uint8_t GetP() const { return m_P; } + uint32_t GetN() const { return m_N; } + uint32_t GetM() const { return m_M; } + const std::vector<unsigned char>& GetEncoded() const { return m_encoded; } + + /** + * Checks if the element may be in the set. False positives are possible + * with probability 1/M. + */ + bool Match(const Element& element) const; + + /** + * Checks if any of the given elements may be in the set. False positives + * are possible with probability 1/M per element checked. This is more + * efficient that checking Match on multiple elements separately. + */ + bool MatchAny(const ElementSet& elements) const; +}; + +constexpr uint8_t BASIC_FILTER_P = 19; +constexpr uint32_t BASIC_FILTER_M = 784931; + +enum BlockFilterType : uint8_t +{ + BASIC = 0, +}; + +/** + * Complete block filter struct as defined in BIP 157. Serialization matches + * payload of "cfilter" messages. + */ +class BlockFilter +{ +private: + BlockFilterType m_filter_type; + uint256 m_block_hash; + GCSFilter m_filter; + +public: + + // Construct a new BlockFilter of the specified type from a block. + BlockFilter(BlockFilterType filter_type, const CBlock& block, const CBlockUndo& block_undo); + + BlockFilterType GetFilterType() const { return m_filter_type; } + + const GCSFilter& GetFilter() const { return m_filter; } + + const std::vector<unsigned char>& GetEncodedFilter() const + { + return m_filter.GetEncoded(); + } + + // Compute the filter hash. + uint256 GetHash() const; + + // Compute the filter header given the previous one. + uint256 ComputeHeader(const uint256& prev_header) const; + + template <typename Stream> + void Serialize(Stream& s) const { + s << m_block_hash + << static_cast<uint8_t>(m_filter_type) + << m_filter.GetEncoded(); + } + + template <typename Stream> + void Unserialize(Stream& s) { + std::vector<unsigned char> encoded_filter; + uint8_t filter_type; + + s >> m_block_hash + >> filter_type + >> encoded_filter; + + m_filter_type = static_cast<BlockFilterType>(filter_type); + + switch (m_filter_type) { + case BlockFilterType::BASIC: + m_filter = GCSFilter(m_block_hash.GetUint64(0), m_block_hash.GetUint64(1), + BASIC_FILTER_P, BASIC_FILTER_M, std::move(encoded_filter)); + break; + + default: + throw std::ios_base::failure("unknown filter_type"); + } + } +}; + +#endif // BITCOIN_BLOCKFILTER_H |