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 <primitives/block.h>
      15             : #include <serialize.h>
      16             : #include <uint256.h>
      17             : #include <undo.h>
      18             : #include <util/bytevectorhash.h>
      19             : 
      20             : /**
      21             :  * This implements a Golomb-coded set as defined in BIP 158. It is a
      22             :  * compact, probabilistic data structure for testing set membership.
      23             :  */
      24       25456 : class GCSFilter
      25             : {
      26             : public:
      27             :     typedef std::vector<unsigned char> Element;
      28             :     typedef std::unordered_set<Element, ByteVectorHash> ElementSet;
      29             : 
      30             :     struct Params
      31             :     {
      32             :         uint64_t m_siphash_k0;
      33             :         uint64_t m_siphash_k1;
      34             :         uint8_t m_P;  //!< Golomb-Rice coding parameter
      35             :         uint32_t m_M;  //!< Inverse false positive rate
      36             : 
      37       20184 :         Params(uint64_t siphash_k0 = 0, uint64_t siphash_k1 = 0, uint8_t P = 0, uint32_t M = 1)
      38       10092 :             : m_siphash_k0(siphash_k0), m_siphash_k1(siphash_k1), m_P(P), m_M(M)
      39       20184 :         {}
      40             :     };
      41             : 
      42             : private:
      43             :     Params m_params;
      44             :     uint32_t m_N;  //!< Number of elements in the filter
      45             :     uint64_t m_F;  //!< Range of element hashes, F = N * M
      46             :     std::vector<unsigned char> m_encoded;
      47             : 
      48             :     /** Hash a data element to an integer in the range [0, N * M). */
      49             :     uint64_t HashToRange(const Element& element) const;
      50             : 
      51             :     std::vector<uint64_t> BuildHashedSet(const ElementSet& elements) const;
      52             : 
      53             :     /** Helper method used to implement Match and MatchAny */
      54             :     bool MatchInternal(const uint64_t* sorted_element_hashes, size_t size) const;
      55             : 
      56             : public:
      57             : 
      58             :     /** Constructs an empty filter. */
      59             :     explicit GCSFilter(const Params& params = Params());
      60             : 
      61             :     /** Reconstructs an already-created filter from an encoding. */
      62             :     GCSFilter(const Params& params, std::vector<unsigned char> encoded_filter);
      63             : 
      64             :     /** Builds a new filter from the params and set of elements. */
      65             :     GCSFilter(const Params& params, const ElementSet& elements);
      66             : 
      67           1 :     uint32_t GetN() const { return m_N; }
      68           1 :     const Params& GetParams() const { return m_params; }
      69       18020 :     const std::vector<unsigned char>& GetEncoded() const { return m_encoded; }
      70             : 
      71             :     /**
      72             :      * Checks if the element may be in the set. False positives are possible
      73             :      * with probability 1/M.
      74             :      */
      75             :     bool Match(const Element& element) const;
      76             : 
      77             :     /**
      78             :      * Checks if any of the given elements may be in the set. False positives
      79             :      * are possible with probability 1/M per element checked. This is more
      80             :      * efficient that checking Match on multiple elements separately.
      81             :      */
      82             :     bool MatchAny(const ElementSet& elements) const;
      83             : };
      84             : 
      85             : constexpr uint8_t BASIC_FILTER_P = 19;
      86             : constexpr uint32_t BASIC_FILTER_M = 784931;
      87             : 
      88             : enum class BlockFilterType : uint8_t
      89             : {
      90             :     BASIC = 0,
      91             :     INVALID = 255,
      92             : };
      93             : 
      94             : /** Get the human-readable name for a filter type. Returns empty string for unknown types. */
      95             : const std::string& BlockFilterTypeName(BlockFilterType filter_type);
      96             : 
      97             : /** Find a filter type by its human-readable name. */
      98             : bool BlockFilterTypeByName(const std::string& name, BlockFilterType& filter_type);
      99             : 
     100             : /** Get a list of known filter types. */
     101             : const std::set<BlockFilterType>& AllBlockFilterTypes();
     102             : 
     103             : /** Get a comma-separated list of known filter type names. */
     104             : const std::string& ListBlockFilterTypes();
     105             : 
     106             : /**
     107             :  * Complete block filter struct as defined in BIP 157. Serialization matches
     108             :  * payload of "cfilter" messages.
     109             :  */
     110       11019 : class BlockFilter
     111             : {
     112             : private:
     113         473 :     BlockFilterType m_filter_type = BlockFilterType::INVALID;
     114             :     uint256 m_block_hash;
     115             :     GCSFilter m_filter;
     116             : 
     117             :     bool BuildParams(GCSFilter::Params& params) const;
     118             : 
     119             : public:
     120             : 
     121         946 :     BlockFilter() = default;
     122             : 
     123             :     //! Reconstruct a BlockFilter from parts.
     124             :     BlockFilter(BlockFilterType filter_type, const uint256& block_hash,
     125             :                 std::vector<unsigned char> filter);
     126             : 
     127             :     //! Construct a new BlockFilter of the specified type from a block.
     128             :     BlockFilter(BlockFilterType filter_type, const CBlock& block, const CBlockUndo& block_undo);
     129             : 
     130        4326 :     BlockFilterType GetFilterType() const { return m_filter_type; }
     131        8648 :     const uint256& GetBlockHash() const { return m_block_hash; }
     132          11 :     const GCSFilter& GetFilter() const { return m_filter; }
     133             : 
     134       17997 :     const std::vector<unsigned char>& GetEncodedFilter() const
     135             :     {
     136       17997 :         return m_filter.GetEncoded();
     137             :     }
     138             : 
     139             :     //! Compute the filter hash.
     140             :     uint256 GetHash() const;
     141             : 
     142             :     //! Compute the filter header given the previous one.
     143             :     uint256 ComputeHeader(const uint256& prev_header) const;
     144             : 
     145             :     template <typename Stream>
     146          12 :     void Serialize(Stream& s) const {
     147          12 :         s << static_cast<uint8_t>(m_filter_type)
     148          12 :           << m_block_hash
     149          12 :           << m_filter.GetEncoded();
     150          12 :     }
     151             : 
     152             :     template <typename Stream>
     153           1 :     void Unserialize(Stream& s) {
     154           1 :         std::vector<unsigned char> encoded_filter;
     155           1 :         uint8_t filter_type;
     156             : 
     157           1 :         s >> filter_type
     158           1 :           >> m_block_hash
     159           1 :           >> encoded_filter;
     160             : 
     161           1 :         m_filter_type = static_cast<BlockFilterType>(filter_type);
     162             : 
     163           1 :         GCSFilter::Params params;
     164           1 :         if (!BuildParams(params)) {
     165           0 :             throw std::ios_base::failure("unknown filter_type");
     166             :         }
     167           1 :         m_filter = GCSFilter(params, std::move(encoded_filter));
     168           1 :     }
     169             : };
     170             : 
     171             : #endif // BITCOIN_BLOCKFILTER_H