diff options
Diffstat (limited to 'src/blockfilter.cpp')
-rw-r--r-- | src/blockfilter.cpp | 31 |
1 files changed, 0 insertions, 31 deletions
diff --git a/src/blockfilter.cpp b/src/blockfilter.cpp index 69d4eacd87..b797639d12 100644 --- a/src/blockfilter.cpp +++ b/src/blockfilter.cpp @@ -24,37 +24,6 @@ static const std::map<BlockFilterType, std::string> g_filter_types = { {BlockFilterType::BASIC, "basic"}, }; -// 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) |