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75 lines
2.2 KiB
C++
75 lines
2.2 KiB
C++
#include <type_traits>
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#include <ext/bit_cast.h>
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#include <Functions/FunctionFactory.h>
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#include <Functions/FunctionUnaryArithmetic.h>
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namespace DB
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{
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template <typename T>
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inline std::enable_if_t<is_integral_v<T> && (sizeof(T) <= sizeof(UInt32)), T>
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roundDownToPowerOfTwo(T x)
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{
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return x <= 0 ? 0 : (T(1) << (31 - __builtin_clz(x)));
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}
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template <typename T>
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inline std::enable_if_t<is_integral_v<T> && (sizeof(T) == sizeof(UInt64)), T>
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roundDownToPowerOfTwo(T x)
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{
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return x <= 0 ? 0 : (T(1) << (63 - __builtin_clzll(x)));
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}
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template <typename T>
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inline std::enable_if_t<std::is_same_v<T, Float32>, T>
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roundDownToPowerOfTwo(T x)
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{
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return ext::bit_cast<T>(ext::bit_cast<UInt32>(x) & ~((1ULL << 23) - 1));
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}
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template <typename T>
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inline std::enable_if_t<std::is_same_v<T, Float64>, T>
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roundDownToPowerOfTwo(T x)
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{
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return ext::bit_cast<T>(ext::bit_cast<UInt64>(x) & ~((1ULL << 52) - 1));
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}
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/** For integer data types:
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* - if number is greater than zero, round it down to nearest power of two (example: roundToExp2(100) = 64, roundToExp2(64) = 64);
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* - otherwise, return 0.
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*
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* For floating point data types: zero out mantissa, but leave exponent.
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* - if number is greater than zero, round it down to nearest power of two (example: roundToExp2(3) = 2);
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* - negative powers are also used (example: roundToExp2(0.7) = 0.5);
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* - if number is zero, return zero;
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* - if number is less than zero, the result is symmetrical: roundToExp2(x) = -roundToExp2(-x). (example: roundToExp2(-0.3) = -0.25);
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*/
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template <typename T>
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struct RoundToExp2Impl
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{
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using ResultType = T;
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static constexpr const bool allow_fixed_string = false;
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static inline T apply(T x)
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{
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return roundDownToPowerOfTwo<T>(x);
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}
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#if USE_EMBEDDED_COMPILER
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static constexpr bool compilable = false;
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#endif
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};
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struct NameRoundToExp2 { static constexpr auto name = "roundToExp2"; };
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using FunctionRoundToExp2 = FunctionUnaryArithmetic<RoundToExp2Impl, NameRoundToExp2, false>;
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template <> struct FunctionUnaryArithmeticMonotonicity<NameRoundToExp2> : PositiveMonotonicity {};
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void registerFunctionRoundToExp2(FunctionFactory & factory)
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{
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factory.registerFunction<FunctionRoundToExp2>();
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}
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}
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