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#include <base/bit_cast.h>
#include <Functions/FunctionFactory.h>
#include <Functions/FunctionUnaryArithmetic.h>
namespace DB
{
template <typename A>
struct BitCountImpl
{
using ResultType = std::conditional_t<(sizeof(A) * 8 >= 256), UInt16, UInt8>;
static constexpr bool allow_string_or_fixed_string = true;
static inline ResultType apply(A a)
{
/// We count bits in the value representation in memory. For example, we support floats.
/// We need to avoid sign-extension when converting signed numbers to larger type. So, uint8_t(-1) has 8 bits.
if constexpr (is_big_int_v<A>)
{
ResultType res = 0;
for (auto item : a.items)
res += __builtin_popcountll(item);
return res;
}
if constexpr (std::is_same_v<A, UInt64> || std::is_same_v<A, Int64>)
return __builtin_popcountll(a);
if constexpr (std::is_same_v<A, UInt32> || std::is_same_v<A, Int32> || std::is_unsigned_v<A>)
return __builtin_popcount(a);
if constexpr (std::is_same_v<A, Int16>)
return __builtin_popcount(static_cast<UInt16>(a));
if constexpr (std::is_same_v<A, Int8>)
return __builtin_popcount(static_cast<UInt8>(a));
else
return __builtin_popcountll(bit_cast<uint64_t>(a));
}
#if USE_EMBEDDED_COMPILER
static constexpr bool compilable = false;
#endif
};
struct NameBitCount { static constexpr auto name = "bitCount"; };
using FunctionBitCount = FunctionUnaryArithmetic<BitCountImpl, NameBitCount, false /* is injective */>;
/// The function has no ranges of monotonicity.
template <> struct FunctionUnaryArithmeticMonotonicity<NameBitCount>
{
static bool has() { return false; }
static IFunction::Monotonicity get(const Field &, const Field &)
{
return {};
}
};
REGISTER_FUNCTION(BitCount)
{
factory.registerFunction<FunctionBitCount>();
}
}
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