1 files changed, 278 insertions, 0 deletions
diff --git a/src/blockfilter.cpp b/src/blockfilter.cpp
new file mode 100644
index 0000000000..bcf24047ff
--- /dev/null
+++ b/src/blockfilter.cpp
@@ -0,0 +1,278 @@
+// 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.
+
+#include <blockfilter.h>
+#include <crypto/siphash.h>
+#include <hash.h>
+#include <primitives/transaction.h>
+#include <script/script.h>
+#include <streams.h>
+
+/// SerType used to serialize parameters in GCS filter encoding.
+static constexpr int GCS_SER_TYPE = SER_NETWORK;
+
+/// Protocol version used to serialize parameters in GCS filter encoding.
+static constexpr int GCS_SER_VERSION = 0;
+
+template <typename OStream>
+static void GolombRiceEncode(BitStreamWriter<OStream>& bitwriter, uint8_t P, uint64_t x)
+{
+    // Write quotient as unary-encoded: q 1's followed by one 0.
+    uint64_t q = x >> P;
+    while (q > 0) {
+        int nbits = q <= 64 ? static_cast<int>(q) : 64;
+        bitwriter.Write(~0ULL, nbits);
+        q -= nbits;
+    }
+    bitwriter.Write(0, 1);
+
+    // Write the remainder in P bits. Since the remainder is just the bottom
+    // P bits of x, there is no need to mask first.
+    bitwriter.Write(x, P);
+}
+
+template <typename IStream>
+static uint64_t GolombRiceDecode(BitStreamReader<IStream>& bitreader, uint8_t P)
+{
+    // Read unary-encoded quotient: q 1's followed by one 0.
+    uint64_t q = 0;
+    while (bitreader.Read(1) == 1) {
+        ++q;
+    }
+
+    uint64_t r = bitreader.Read(P);
+
+    return (q << P) + r;
+}
+
+// Map a value x that is uniformly distributed in the range [0, 2^64) to a
+// value uniformly distributed in [0, n) by returning the upper 64 bits of
+// x * n.
+//
+// See: https://lemire.me/blog/2016/06/27/a-fast-alternative-to-the-modulo-reduction/
+static uint64_t MapIntoRange(uint64_t x, uint64_t n)
+{
+#ifdef __SIZEOF_INT128__
+    return (static_cast<unsigned __int128>(x) * static_cast<unsigned __int128>(n)) >> 64;
+#else
+    // To perform the calculation on 64-bit numbers without losing the
+    // result to overflow, split the numbers into the most significant and
+    // least significant 32 bits and perform multiplication piece-wise.
+    //
+    // See: https://stackoverflow.com/a/26855440
+    uint64_t x_hi = x >> 32;
+    uint64_t x_lo = x & 0xFFFFFFFF;
+    uint64_t n_hi = n >> 32;
+    uint64_t n_lo = n & 0xFFFFFFFF;
+
+    uint64_t ac = x_hi * n_hi;
+    uint64_t ad = x_hi * n_lo;
+    uint64_t bc = x_lo * n_hi;
+    uint64_t bd = x_lo * n_lo;
+
+    uint64_t mid34 = (bd >> 32) + (bc & 0xFFFFFFFF) + (ad & 0xFFFFFFFF);
+    uint64_t upper64 = ac + (bc >> 32) + (ad >> 32) + (mid34 >> 32);
+    return upper64;
+#endif
+}
+
+uint64_t GCSFilter::HashToRange(const Element& element) const
+{
+    uint64_t hash = CSipHasher(m_params.m_siphash_k0, m_params.m_siphash_k1)
+        .Write(element.data(), element.size())
+        .Finalize();
+    return MapIntoRange(hash, m_F);
+}
+
+std::vector<uint64_t> GCSFilter::BuildHashedSet(const ElementSet& elements) const
+{
+    std::vector<uint64_t> hashed_elements;
+    hashed_elements.reserve(elements.size());
+    for (const Element& element : elements) {
+        hashed_elements.push_back(HashToRange(element));
+    }
+    std::sort(hashed_elements.begin(), hashed_elements.end());
+    return hashed_elements;
+}
+
+GCSFilter::GCSFilter(const Params& params)
+    : m_params(params), m_N(0), m_F(0), m_encoded{0}
+{}
+
+GCSFilter::GCSFilter(const Params& params, std::vector<unsigned char> encoded_filter)
+    : m_params(params), m_encoded(std::move(encoded_filter))
+{
+    VectorReader stream(GCS_SER_TYPE, GCS_SER_VERSION, m_encoded, 0);
+
+    uint64_t N = ReadCompactSize(stream);
+    m_N = static_cast<uint32_t>(N);
+    if (m_N != N) {
+        throw std::ios_base::failure("N must be <2^32");
+    }
+    m_F = static_cast<uint64_t>(m_N) * static_cast<uint64_t>(m_params.m_M);
+
+    // Verify that the encoded filter contains exactly N elements. If it has too much or too little
+    // data, a std::ios_base::failure exception will be raised.
+    BitStreamReader<VectorReader> bitreader(stream);
+    for (uint64_t i = 0; i < m_N; ++i) {
+        GolombRiceDecode(bitreader, m_params.m_P);
+    }
+    if (!stream.empty()) {
+        throw std::ios_base::failure("encoded_filter contains excess data");
+    }
+}
+
+GCSFilter::GCSFilter(const Params& params, const ElementSet& elements)
+    : m_params(params)
+{
+    size_t N = elements.size();
+    m_N = static_cast<uint32_t>(N);
+    if (m_N != N) {
+        throw std::invalid_argument("N must be <2^32");
+    }
+    m_F = static_cast<uint64_t>(m_N) * static_cast<uint64_t>(m_params.m_M);
+
+    CVectorWriter stream(GCS_SER_TYPE, GCS_SER_VERSION, m_encoded, 0);
+
+    WriteCompactSize(stream, m_N);
+
+    if (elements.empty()) {
+        return;
+    }
+
+    BitStreamWriter<CVectorWriter> bitwriter(stream);
+
+    uint64_t last_value = 0;
+    for (uint64_t value : BuildHashedSet(elements)) {
+        uint64_t delta = value - last_value;
+        GolombRiceEncode(bitwriter, m_params.m_P, delta);
+        last_value = value;
+    }
+
+    bitwriter.Flush();
+}
+
+bool GCSFilter::MatchInternal(const uint64_t* element_hashes, size_t size) const
+{
+    VectorReader stream(GCS_SER_TYPE, GCS_SER_VERSION, m_encoded, 0);
+
+    // Seek forward by size of N
+    uint64_t N = ReadCompactSize(stream);
+    assert(N == m_N);
+
+    BitStreamReader<VectorReader> bitreader(stream);
+
+    uint64_t value = 0;
+    size_t hashes_index = 0;
+    for (uint32_t i = 0; i < m_N; ++i) {
+        uint64_t delta = GolombRiceDecode(bitreader, m_params.m_P);
+        value += delta;
+
+        while (true) {
+            if (hashes_index == size) {
+                return false;
+            } else if (element_hashes[hashes_index] == value) {
+                return true;
+            } else if (element_hashes[hashes_index] > value) {
+                break;
+            }
+
+            hashes_index++;
+        }
+    }
+
+    return false;
+}
+
+bool GCSFilter::Match(const Element& element) const
+{
+    uint64_t query = HashToRange(element);
+    return MatchInternal(&query, 1);
+}
+
+bool GCSFilter::MatchAny(const ElementSet& elements) const
+{
+    const std::vector<uint64_t> queries = BuildHashedSet(elements);
+    return MatchInternal(queries.data(), queries.size());
+}
+
+static GCSFilter::ElementSet BasicFilterElements(const CBlock& block,
+                                                 const CBlockUndo& block_undo)
+{
+    GCSFilter::ElementSet elements;
+
+    for (const CTransactionRef& tx : block.vtx) {
+        for (const CTxOut& txout : tx->vout) {
+            const CScript& script = txout.scriptPubKey;
+            if (script.empty() || script[0] == OP_RETURN) continue;
+            elements.emplace(script.begin(), script.end());
+        }
+    }
+
+    for (const CTxUndo& tx_undo : block_undo.vtxundo) {
+        for (const Coin& prevout : tx_undo.vprevout) {
+            const CScript& script = prevout.out.scriptPubKey;
+            if (script.empty()) continue;
+            elements.emplace(script.begin(), script.end());
+        }
+    }
+
+    return elements;
+}
+
+BlockFilter::BlockFilter(BlockFilterType filter_type, const uint256& block_hash,
+                         std::vector<unsigned char> filter)
+    : m_filter_type(filter_type), m_block_hash(block_hash)
+{
+    GCSFilter::Params params;
+    if (!BuildParams(params)) {
+        throw std::invalid_argument("unknown filter_type");
+    }
+    m_filter = GCSFilter(params, std::move(filter));
+}
+
+BlockFilter::BlockFilter(BlockFilterType filter_type, const CBlock& block, const CBlockUndo& block_undo)
+    : m_filter_type(filter_type), m_block_hash(block.GetHash())
+{
+    GCSFilter::Params params;
+    if (!BuildParams(params)) {
+        throw std::invalid_argument("unknown filter_type");
+    }
+    m_filter = GCSFilter(params, BasicFilterElements(block, block_undo));
+}
+
+bool BlockFilter::BuildParams(GCSFilter::Params& params) const
+{
+    switch (m_filter_type) {
+    case BlockFilterType::BASIC:
+        params.m_siphash_k0 = m_block_hash.GetUint64(0);
+        params.m_siphash_k1 = m_block_hash.GetUint64(1);
+        params.m_P = BASIC_FILTER_P;
+        params.m_M = BASIC_FILTER_M;
+        return true;
+    }
+
+    return false;
+}
+
+uint256 BlockFilter::GetHash() const
+{
+    const std::vector<unsigned char>& data = GetEncodedFilter();
+
+    uint256 result;
+    CHash256().Write(data.data(), data.size()).Finalize(result.begin());
+    return result;
+}
+
+uint256 BlockFilter::ComputeHeader(const uint256& prev_header) const
+{
+    const uint256& filter_hash = GetHash();
+
+    uint256 result;
+    CHash256()
+        .Write(filter_hash.begin(), filter_hash.size())
+        .Write(prev_header.begin(), prev_header.size())
+        .Finalize(result.begin());
+    return result;
+}