ClickHouse/dbms/include/DB/IO/DoubleConverter.h

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#pragma once
#include <double-conversion/double-conversion.h>
namespace DB
{
template <bool emit_decimal_point> struct DoubleToStringConverterFlags
{
static constexpr auto flags = double_conversion::DoubleToStringConverter::NO_FLAGS;
};
template <> struct DoubleToStringConverterFlags<true>
{
static constexpr auto flags = double_conversion::DoubleToStringConverter::EMIT_TRAILING_DECIMAL_POINT;
};
template <bool emit_decimal_point>
class DoubleConverter
{
DoubleConverter(const DoubleConverter &) = delete;
DoubleConverter & operator=(const DoubleConverter &) = delete;
DoubleConverter() = default;
public:
/** @todo Add commentary on how this constant is deduced.
* e.g. it's minus sign, integral zero, decimal point, up to 5 leading zeros and kBase10MaximalLength digits. */
static constexpr auto MAX_REPRESENTATION_LENGTH = 26;
using BufferType = char[MAX_REPRESENTATION_LENGTH];
static const auto & instance()
{
static const double_conversion::DoubleToStringConverter instance{
DoubleToStringConverterFlags<emit_decimal_point>::flags, "inf", "nan", 'e', -6, 21, 6, 1
};
return instance;
}
};
}