ClickHouse/dbms/include/DB/Functions/FunctionsRound.h

#pragma once

#include <DB/Functions/FunctionsArithmetic.h>
#include <cmath>	// log2()


namespace DB
{
	
	/** Функции округления:
	 * roundToExp2 - вниз до ближайшей степени двойки;
	 * roundDuration - вниз до ближайшего из: 0, 1, 10, 30, 60, 120, 180, 240, 300, 600, 1200, 1800, 3600, 7200, 18000, 36000;
	 * roundAge - вниз до ближайшего из: 0, 18, 25, 35, 45.
	 */
	
	template<typename A>
	struct RoundToExp2Impl
	{
		typedef A ResultType;
		
		static inline A apply(A x)
		{
			return x <= 0 ? static_cast<A>(0) : (static_cast<A>(1) << static_cast<UInt64>(log2(static_cast<double>(x))));
		}
	};
	
	template<>
	struct RoundToExp2Impl<Float32>
	{
		typedef Float32 ResultType;
		
		static inline Float32 apply(Float32 x)
		{
			return static_cast<Float32>(x < 1 ? 0. : pow(2., floor(log2(x))));
		}
	};
	
	template<>
	struct RoundToExp2Impl<Float64>
	{
		typedef Float64 ResultType;
		
		static inline Float64 apply(Float64 x)
		{
			return x < 1 ? 0. : pow(2., floor(log2(x)));
		}
	};
	
	template<typename A>
	struct RoundDurationImpl
	{
		typedef UInt16 ResultType;
		
		static inline ResultType apply(A x)
		{
			return x < 1 ? 0
				: (x < 10 ? 1
				: (x < 30 ? 10
				: (x < 60 ? 30
				: (x < 120 ? 60
				: (x < 180 ? 120
				: (x < 240 ? 180
				: (x < 300 ? 240
				: (x < 600 ? 300
				: (x < 1200 ? 600
				: (x < 1800 ? 1200
				: (x < 3600 ? 1800
				: (x < 7200 ? 3600
				: (x < 18000 ? 7200
				: (x < 36000 ? 18000
				: 36000))))))))))))));
		}
	};
	
	template<typename A>
	struct RoundAgeImpl
	{
		typedef UInt8 ResultType;
		
		static inline ResultType apply(A x)
		{
			return x < 18 ? 0
				: (x < 25 ? 18
				: (x < 35 ? 25
				: (x < 45 ? 35
				: 45)));
		}
	};
	
	
	struct NameRoundToExp2		{ static const char * get() { return "roundToExp2"; } };
	struct NameRoundDuration	{ static const char * get() { return "roundDuration"; } };
	struct NameRoundAge 		{ static const char * get() { return "roundAge"; } };
	
	typedef FunctionUnaryArithmetic<RoundToExp2Impl,	NameRoundToExp2> 	FunctionRoundToExp2;
	typedef FunctionUnaryArithmetic<RoundDurationImpl,	NameRoundDuration>	FunctionRoundDuration;
	typedef FunctionUnaryArithmetic<RoundAgeImpl,		NameRoundAge>		FunctionRoundAge;
	
}