Line data    Source code

       1             : // Copyright (c) 2018-2019 The Bitcoin Core developers
       2             : // Distributed under the MIT software license, see the accompanying
       3             : // file COPYING or http://www.opensource.org/licenses/mit-license.php.
       4             : 
       5             : #ifndef BITCOIN_BLOCKFILTER_H
       6             : #define BITCOIN_BLOCKFILTER_H
       7             : 
       8             : #include <stdint.h>
       9             : #include <string>
      10             : #include <set>
      11             : #include <unordered_set>
      12             : #include <vector>
      13             : 
      14             : #include <attributes.h>
      15             : #include <primitives/block.h>
      16             : #include <serialize.h>
      17             : #include <uint256.h>
      18             : #include <undo.h>
      19             : #include <util/bytevectorhash.h>
      20             : 
      21             : /**
      22             :  * This implements a Golomb-coded set as defined in BIP 158. It is a
      23             :  * compact, probabilistic data structure for testing set membership.
      24             :  */
      25             : class GCSFilter
      26             : {
      27             : public:
      28             :     typedef std::vector<unsigned char> Element;
      29             :     typedef std::unordered_set<Element, ByteVectorHash> ElementSet;
      30             : 
      31             :     struct Params
      32             :     {
      33             :         uint64_t m_siphash_k0;
      34             :         uint64_t m_siphash_k1;
      35             :         uint8_t m_P;  //!< Golomb-Rice coding parameter
      36             :         uint32_t m_M;  //!< Inverse false positive rate
      37             : 
      38        3176 :         Params(uint64_t siphash_k0 = 0, uint64_t siphash_k1 = 0, uint8_t P = 0, uint32_t M = 1)
      39        1588 :             : m_siphash_k0(siphash_k0), m_siphash_k1(siphash_k1), m_P(P), m_M(M)
      40        3176 :         {}
      41             :     };
      42             : 
      43             : private:
      44             :     Params m_params;
      45             :     uint32_t m_N;  //!< Number of elements in the filter
      46             :     uint64_t m_F;  //!< Range of element hashes, F = N * M
      47             :     std::vector<unsigned char> m_encoded;
      48             : 
      49             :     /** Hash a data element to an integer in the range [0, N * M). */
      50             :     uint64_t HashToRange(const Element& element) const;
      51             : 
      52             :     std::vector<uint64_t> BuildHashedSet(const ElementSet& elements) const;
      53             : 
      54             :     /** Helper method used to implement Match and MatchAny */
      55             :     bool MatchInternal(const uint64_t* sorted_element_hashes, size_t size) const;
      56             : 
      57             : public:
      58             : 
      59             :     /** Constructs an empty filter. */
      60             :     explicit GCSFilter(const Params& params = Params());
      61             : 
      62             :     /** Reconstructs an already-created filter from an encoding. */
      63             :     GCSFilter(const Params& params, std::vector<unsigned char> encoded_filter, bool skip_decode_check);
      64             : 
      65             :     /** Builds a new filter from the params and set of elements. */
      66             :     GCSFilter(const Params& params, const ElementSet& elements);
      67             : 
      68           1 :     uint32_t GetN() const { return m_N; }
      69           1 :     const Params& GetParams() const LIFETIMEBOUND { return m_params; }
      70        1144 :     const std::vector<unsigned char>& GetEncoded() const LIFETIMEBOUND { return m_encoded; }
      71             : 
      72             :     /**
      73             :      * Checks if the element may be in the set. False positives are possible
      74             :      * with probability 1/M.
      75             :      */
      76             :     bool Match(const Element& element) const;
      77             : 
      78             :     /**
      79             :      * Checks if any of the given elements may be in the set. False positives
      80             :      * are possible with probability 1/M per element checked. This is more
      81             :      * efficient that checking Match on multiple elements separately.
      82             :      */
      83             :     bool MatchAny(const ElementSet& elements) const;
      84             : };
      85             : 
      86             : constexpr uint8_t BASIC_FILTER_P = 19;
      87             : constexpr uint32_t BASIC_FILTER_M = 784931;
      88             : 
      89             : enum class BlockFilterType : uint8_t
      90             : {
      91             :     BASIC_FILTER = 0,
      92             :     INVALID = 255,
      93             : };
      94             : 
      95             : /** Get the human-readable name for a filter type. Returns empty string for unknown types. */
      96             : const std::string& BlockFilterTypeName(BlockFilterType filter_type);
      97             : 
      98             : /** Find a filter type by its human-readable name. */
      99             : bool BlockFilterTypeByName(const std::string& name, BlockFilterType& filter_type);
     100             : 
     101             : /** Get a list of known filter types. */
     102             : const std::set<BlockFilterType>& AllBlockFilterTypes();
     103             : 
     104             : /** Get a comma-separated list of known filter type names. */
     105             : const std::string& ListBlockFilterTypes();
     106             : 
     107             : /**
     108             :  * Complete block filter struct as defined in BIP 157. Serialization matches
     109             :  * payload of "cfilter" messages.
     110             :  */
     111             : class BlockFilter
     112             : {
     113             : private:
     114         451 :     BlockFilterType m_filter_type = BlockFilterType::INVALID;
     115             :     uint256 m_block_hash;
     116             :     GCSFilter m_filter;
     117             : 
     118             :     bool BuildParams(GCSFilter::Params& params) const;
     119             : 
     120             : public:
     121             : 
     122        1353 :     BlockFilter() = default;
     123             : 
     124             :     //! Reconstruct a BlockFilter from parts.
     125             :     BlockFilter(BlockFilterType filter_type, const uint256& block_hash,
     126             :                 std::vector<unsigned char> filter, bool skip_decode_check);
     127             : 
     128             :     //! Construct a new BlockFilter of the specified type from a block.
     129             :     BlockFilter(BlockFilterType filter_type, const CBlock& block, const CBlockUndo& block_undo);
     130             : 
     131         114 :     BlockFilterType GetFilterType() const { return m_filter_type; }
     132         224 :     const uint256& GetBlockHash() const LIFETIMEBOUND { return m_block_hash; }
     133          10 :     const GCSFilter& GetFilter() const LIFETIMEBOUND { return m_filter; }
     134             : 
     135        1135 :     const std::vector<unsigned char>& GetEncodedFilter() const LIFETIMEBOUND
     136             :     {
     137        1135 :         return m_filter.GetEncoded();
     138             :     }
     139             : 
     140             :     //! Compute the filter hash.
     141             :     uint256 GetHash() const;
     142             : 
     143             :     //! Compute the filter header given the previous one.
     144             :     uint256 ComputeHeader(const uint256& prev_header) const;
     145             : 
     146             :     template <typename Stream>
     147           1 :     void Serialize(Stream& s) const {
     148           1 :         s << static_cast<uint8_t>(m_filter_type)
     149           1 :           << m_block_hash
     150           1 :           << m_filter.GetEncoded();
     151           1 :     }
     152             : 
     153             :     template <typename Stream>
     154           1 :     void Unserialize(Stream& s) {
     155           1 :         std::vector<unsigned char> encoded_filter;
     156             :         uint8_t filter_type;
     157             : 
     158           1 :         s >> filter_type
     159           1 :           >> m_block_hash
     160           1 :           >> encoded_filter;
     161             : 
     162           1 :         m_filter_type = static_cast<BlockFilterType>(filter_type);
     163             : 
     164           1 :         GCSFilter::Params params;
     165           1 :         if (!BuildParams(params)) {
     166           0 :             throw std::ios_base::failure("unknown filter_type");
     167             :         }
     168           1 :         m_filter = GCSFilter(params, std::move(encoded_filter), /*skip_decode_check=*/false);
     169           1 :     }
     170             : };
     171             : 
     172             : #endif // BITCOIN_BLOCKFILTER_H