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

#ifndef DBMS_COMMON_WRITEHELPERS_H
#define DBMS_COMMON_WRITEHELPERS_H

#include <cstring>
#include <cstdio>
#include <limits>
#include <algorithm>

#include <Yandex/DateLUT.h>

#include <DB/Core/Types.h>
#include <DB/Core/Exception.h>
#include <DB/Core/ErrorCodes.h>

#include <DB/IO/WriteBuffer.h>

#define WRITE_HELPERS_DEFAULT_FLOAT_PRECISION 6U
/// 20 цифр и знак
#define WRITE_HELPERS_MAX_INT_WIDTH 21U


namespace DB
{

/// Функции-помошники для форматированной записи

inline void writeChar(char x, WriteBuffer & buf)
{
	buf.nextIfAtEnd();
	*buf.position() = x;
	++buf.position();
}


template <typename T>
void writeIntText(T x, WriteBuffer & buf)
{
	char tmp[WRITE_HELPERS_MAX_INT_WIDTH];
	bool negative = false;

	if (x == 0)
	{
		writeChar('0', buf);
		return;
	}

	if (x < 0)
	{
		x = -x;
		negative = true;
	}

	char * pos;
	for (pos = tmp + WRITE_HELPERS_MAX_INT_WIDTH - 1; x != 0; --pos)
	{
		*pos = '0' + x % 10;
		x /= 10;
	}

	if (negative)
		*pos = '-';
	else
		++pos;

	buf.write(pos, tmp + WRITE_HELPERS_MAX_INT_WIDTH - pos);
}

template <typename T>
void writeFloatText(T x, WriteBuffer & buf, unsigned precision = WRITE_HELPERS_DEFAULT_FLOAT_PRECISION)
{
	unsigned size = precision + 10;
	char tmp[size];	/// знаки, +0.0e+123\0
	int res = std::snprintf(tmp, size, "%.*g", precision, x);

	if (res >= static_cast<int>(size) || res <= 0)
		throw Exception("Cannot print float or double number", ErrorCodes::CANNOT_PRINT_FLOAT_OR_DOUBLE_NUMBER);

	buf.write(tmp, res);
}

inline void writeString(const String & s, WriteBuffer & buf)
{
	buf.write(s.data(), s.size());
}

/// предполагается, что строка в оперативке хранится непрерывно, и \0-terminated.
void writeEscapedString(const String & s, WriteBuffer & buf);

inline void writeQuotedString(const String & s, WriteBuffer & buf)
{
	writeChar('\'', buf);
	writeEscapedString(s, buf);
	writeChar('\'', buf);
}


/// в формате YYYY-MM-DD
inline void writeDateText(Yandex::DayNum_t date, WriteBuffer & buf)
{
	char s[10];

	const Yandex::DateLUT::Values & values = Yandex::DateLUTSingleton::instance().getValues(date);

	s[0] = '0' + values.year / 1000;
	s[1] = '0' + (values.year / 100) % 10;
	s[2] = '0' + (values.year / 10) % 10;
	s[3] = '0' + values.year % 10;
	s[4] = '-';
	s[5] = '0' + values.month / 10;
	s[6] = '0' + values.month % 10;
	s[7] = '-';
	s[8] = '0' + values.day_of_month / 10;
	s[9] = '0' + values.day_of_month % 10;
	
	buf.write(s, 10);
}


}

#endif