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tests: Add fuzzing harness for Golomb-Rice coding (GolombRiceEncode/GolombRiceDecode)

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practicalswift
2020-02-21 15:57:02 +00:00
parent 299544f9c5
commit 69749fbe6a
5 changed files with 164 additions and 31 deletions
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32
src/blockfilter.cpp
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@@ -12,6 +12,7 @@
#include <primitives/transaction.h>
#include <script/script.h>
#include <streams.h>
#include <util/golombrice.h>
/// SerType used to serialize parameters in GCS filter encoding.
static constexpr int GCS_SER_TYPE = SER_NETWORK;
@@ -23,37 +24,6 @@ static const std::map<BlockFilterType, std::string> g_filter_types = {
{BlockFilterType::BASIC, "basic"},
};
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.