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

#pragma once

#include <DB/IO/ReadBufferFromString.h>
#include <DB/DataTypes/DataTypesNumber.h>
#include <DB/DataTypes/DataTypeString.h>
#include <DB/DataTypes/DataTypeFixedString.h>
#include <DB/DataTypes/DataTypeDate.h>
#include <DB/DataTypes/DataTypeDateTime.h>
#include <DB/Columns/ColumnString.h>
#include <DB/Columns/ColumnFixedString.h>
#include <DB/Columns/ColumnConst.h>
#include <DB/Functions/IFunction.h>


namespace DB
{

/** Функции преобразования чисел и дат в строки, содержащие тот же набор байт в машинном представлении, и обратно.
	*/


template<typename Name>
class FunctionReinterpretAsStringImpl : public IFunction
{
public:
	static constexpr auto name = Name::name;
	static FunctionPtr create(const Context & context) { return std::make_shared<FunctionReinterpretAsStringImpl>(); };

	String getName() const override
	{
		return name;
	}

	size_t getNumberOfArguments() const override { return 1; }

	DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
	{
		const IDataType * type = &*arguments[0];
		if (!type->isNumeric() &&
			!typeid_cast<const DataTypeDate *>(type) &&
			!typeid_cast<const DataTypeDateTime *>(type))
			throw Exception("Cannot reinterpret " + type->getName() + " as String", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);

		return std::make_shared<DataTypeString>();
	}

	template<typename T>
	bool executeType(Block & block, const ColumnNumbers & arguments, size_t result)
	{
		if (const ColumnVector<T> * col_from = typeid_cast<const ColumnVector<T> *>(block.safeGetByPosition(arguments[0]).column.get()))
		{
			auto col_to = std::make_shared<ColumnString>();
			block.safeGetByPosition(result).column = col_to;

			const typename ColumnVector<T>::Container_t & vec_from = col_from->getData();
			ColumnString::Chars_t & data_to = col_to->getChars();
			ColumnString::Offsets_t & offsets_to = col_to->getOffsets();
			size_t size = vec_from.size();
			data_to.resize(size * (sizeof(T) + 1));
			offsets_to.resize(size);
			int pos = 0;

			for (size_t i = 0; i < size; ++i)
			{
				memcpy(&data_to[pos], &vec_from[i], sizeof(T));

				int len = sizeof(T);
				while (len > 0 && data_to[pos + len - 1] == '\0')
					--len;

				pos += len;
				data_to[pos++] = '\0';

				offsets_to[i] = pos;
			}
			data_to.resize(pos);
		}
		else if (const ColumnConst<T> * col_from = typeid_cast<const ColumnConst<T> *>(block.safeGetByPosition(arguments[0]).column.get()))
		{
			std::string res(reinterpret_cast<const char *>(&col_from->getData()), sizeof(T));
			while (!res.empty() && res[res.length() - 1] == '\0')
				res.erase(res.end() - 1);

			block.safeGetByPosition(result).column = std::make_shared<ColumnConstString>(col_from->size(), res);
		}
		else
		{
			return false;
		}

		return true;
	}

	void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result) override
	{
		if (!(	executeType<UInt8>(block, arguments, result)
			||	executeType<UInt16>(block, arguments, result)
			||	executeType<UInt32>(block, arguments, result)
			||	executeType<UInt64>(block, arguments, result)
			||	executeType<Int8>(block, arguments, result)
			||	executeType<Int16>(block, arguments, result)
			||	executeType<Int32>(block, arguments, result)
			||	executeType<Int64>(block, arguments, result)
			||	executeType<Float32>(block, arguments, result)
			||	executeType<Float64>(block, arguments, result)))
			throw Exception("Illegal column " + block.safeGetByPosition(arguments[0]).column->getName()
			+ " of argument of function " + getName(),
							ErrorCodes::ILLEGAL_COLUMN);
	}
};

template<typename ToDataType, typename Name>
class FunctionReinterpretStringAs : public IFunction
{
public:
	static constexpr auto name = Name::name;
	static FunctionPtr create(const Context & context) { return std::make_shared<FunctionReinterpretStringAs>(); };

	using ToFieldType = typename ToDataType::FieldType;

	String getName() const override
	{
		return name;
	}

	size_t getNumberOfArguments() const override { return 1; }

	DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
	{
		const IDataType * type = &*arguments[0];
		if (!typeid_cast<const DataTypeString *>(type) &&
			!typeid_cast<const DataTypeFixedString *>(type))
			throw Exception("Cannot reinterpret " + type->getName() + " as " + ToDataType().getName(), ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);

		return std::make_shared<ToDataType>();
	}

	void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result) override
	{
		if (ColumnString * col_from = typeid_cast<ColumnString *>(block.safeGetByPosition(arguments[0]).column.get()))
		{
			auto col_res = std::make_shared<ColumnVector<ToFieldType>>();
			block.safeGetByPosition(result).column = col_res;

			ColumnString::Chars_t & data_from = col_from->getChars();
			ColumnString::Offsets_t & offsets_from = col_from->getOffsets();
			size_t size = offsets_from.size();
			typename ColumnVector<ToFieldType>::Container_t & vec_res = col_res->getData();
			vec_res.resize(size);

			size_t offset = 0;
			for (size_t i = 0; i < size; ++i)
			{
				ToFieldType value = 0;
				memcpy(&value, &data_from[offset], std::min(sizeof(ToFieldType), offsets_from[i] - offset - 1));
				vec_res[i] = value;
				offset = offsets_from[i];
			}
		}
		else if (ColumnFixedString * col_from = typeid_cast<ColumnFixedString *>(block.safeGetByPosition(arguments[0]).column.get()))
		{
			auto col_res = std::make_shared<ColumnVector<ToFieldType>>();
			block.safeGetByPosition(result).column = col_res;

			ColumnString::Chars_t & data_from = col_from->getChars();
			size_t step = col_from->getN();
			size_t size = data_from.size() / step;
			typename ColumnVector<ToFieldType>::Container_t & vec_res = col_res->getData();
			vec_res.resize(size);

			size_t offset = 0;
			size_t copy_size = std::min(step, sizeof(ToFieldType));
			for (size_t i = 0; i < size; ++i)
			{
				ToFieldType value = 0;
				memcpy(&value, &data_from[offset], copy_size);
				vec_res[i] = value;
				offset += step;
			}
		}
		else if (ColumnConst<String> * col = typeid_cast<ColumnConst<String> *>(block.safeGetByPosition(arguments[0]).column.get()))
		{
			ToFieldType value = 0;
			const String & str = col->getData();
			memcpy(&value, str.data(), std::min(sizeof(ToFieldType), str.length()));
			auto col_res = std::make_shared<ColumnConst<ToFieldType>>(col->size(), value);
			block.safeGetByPosition(result).column = col_res;
		}
		else
		{
			throw Exception("Illegal column " + block.safeGetByPosition(arguments[0]).column->getName()
			+ " of argument of function " + getName(),
							ErrorCodes::ILLEGAL_COLUMN);
		}
	}
};


struct NameReinterpretAsUInt8 		{ static constexpr auto name = "reinterpretAsUInt8"; };
struct NameReinterpretAsUInt16		{ static constexpr auto name = "reinterpretAsUInt16"; };
struct NameReinterpretAsUInt32		{ static constexpr auto name = "reinterpretAsUInt32"; };
struct NameReinterpretAsUInt64		{ static constexpr auto name = "reinterpretAsUInt64"; };
struct NameReinterpretAsInt8 		{ static constexpr auto name = "reinterpretAsInt8"; };
struct NameReinterpretAsInt16 		{ static constexpr auto name = "reinterpretAsInt16"; };
struct NameReinterpretAsInt32		{ static constexpr auto name = "reinterpretAsInt32"; };
struct NameReinterpretAsInt64		{ static constexpr auto name = "reinterpretAsInt64"; };
struct NameReinterpretAsFloat32		{ static constexpr auto name = "reinterpretAsFloat32"; };
struct NameReinterpretAsFloat64		{ static constexpr auto name = "reinterpretAsFloat64"; };
struct NameReinterpretAsDate		{ static constexpr auto name = "reinterpretAsDate"; };
struct NameReinterpretAsDateTime	{ static constexpr auto name = "reinterpretAsDateTime"; };
struct NameReinterpretAsString		{ static constexpr auto name = "reinterpretAsString"; };

using FunctionReinterpretAsUInt8 = FunctionReinterpretStringAs<DataTypeUInt8,		NameReinterpretAsUInt8>	;
using FunctionReinterpretAsUInt16 = FunctionReinterpretStringAs<DataTypeUInt16,	NameReinterpretAsUInt16>;
using FunctionReinterpretAsUInt32 = FunctionReinterpretStringAs<DataTypeUInt32,	NameReinterpretAsUInt32>;
using FunctionReinterpretAsUInt64 = FunctionReinterpretStringAs<DataTypeUInt64,	NameReinterpretAsUInt64>;
using FunctionReinterpretAsInt8 = FunctionReinterpretStringAs<DataTypeInt8,		NameReinterpretAsInt8>	;
using FunctionReinterpretAsInt16 = FunctionReinterpretStringAs<DataTypeInt16,		NameReinterpretAsInt16>	;
using FunctionReinterpretAsInt32 = FunctionReinterpretStringAs<DataTypeInt32,		NameReinterpretAsInt32>	;
using FunctionReinterpretAsInt64 = FunctionReinterpretStringAs<DataTypeInt64,		NameReinterpretAsInt64>	;
using FunctionReinterpretAsFloat32 = FunctionReinterpretStringAs<DataTypeFloat32,	NameReinterpretAsFloat32>;
using FunctionReinterpretAsFloat64 = FunctionReinterpretStringAs<DataTypeFloat64,	NameReinterpretAsFloat64>;
using FunctionReinterpretAsDate = FunctionReinterpretStringAs<DataTypeDate,		NameReinterpretAsDate>	;
using FunctionReinterpretAsDateTime = FunctionReinterpretStringAs<DataTypeDateTime,	NameReinterpretAsDateTime>;

using FunctionReinterpretAsString = FunctionReinterpretAsStringImpl<NameReinterpretAsString>;


}