duckdb::CountZeros< uint64_t > Struct Reference

Static Public Member Functions
static idx_t	Leading (const uint64_t value_in)
static idx_t	Trailing (uint64_t value_in)

Member Function Documentation

Leading()

static idx_t duckdb::CountZeros< uint64_t >::Leading ( const uint64_t  value_in )

inlinestatic

                                                         {
        if (!value_in) {
            return 64;
        }
 
        uint64_t value = value_in;
 
        constexpr uint64_t index64msb[] = {0,  47, 1,  56, 48, 27, 2,  60, 57, 49, 41, 37, 28, 16, 3,  61,
                                           54, 58, 35, 52, 50, 42, 21, 44, 38, 32, 29, 23, 17, 11, 4,  62,
                                           46, 55, 26, 59, 40, 36, 15, 53, 34, 51, 20, 43, 31, 22, 10, 45,
                                           25, 39, 14, 33, 19, 30, 9,  24, 13, 18, 8,  12, 7,  6,  5,  63};
 
        constexpr uint64_t debruijn64msb = 0X03F79D71B4CB0A89;
 
        value |= value >> 1;
        value |= value >> 2;
        value |= value >> 4;
        value |= value >> 8;
        value |= value >> 16;
        value |= value >> 32;
        auto result = 63 - index64msb[(value * debruijn64msb) >> 58];
#ifdef __clang__
        D_ASSERT(result == static_cast<uint64_t>(__builtin_clzl(value_in)));
#endif
        return result;
    }

Trailing()

static idx_t duckdb::CountZeros< uint64_t >::Trailing ( uint64_t  value_in )

inlinestatic

                                                    {
        if (!value_in) {
            return 64;
        }
        uint64_t value = value_in;
 
        constexpr uint64_t index64lsb[] = {63, 0,  58, 1,  59, 47, 53, 2,  60, 39, 48, 27, 54, 33, 42, 3,
                                           61, 51, 37, 40, 49, 18, 28, 20, 55, 30, 34, 11, 43, 14, 22, 4,
                                           62, 57, 46, 52, 38, 26, 32, 41, 50, 36, 17, 19, 29, 10, 13, 21,
                                           56, 45, 25, 31, 35, 16, 9,  12, 44, 24, 15, 8,  23, 7,  6,  5};
        constexpr uint64_t debruijn64lsb = 0x07EDD5E59A4E28C2ULL;
        auto result = index64lsb[((value & -value) * debruijn64lsb) >> 58];
#ifdef __clang__
        D_ASSERT(result == static_cast<uint64_t>(__builtin_ctzl(value_in)));
#endif
        return result;
    }

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The documentation for this struct was generated from the following file:

• external/duckdb/duckdb.hpp