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

#pragma once

#include <DB/Core/Types.h>
#include <DB/IO/ReadBuffer.h>
#include <DB/IO/WriteBuffer.h>


namespace DB
{


/** Записать UInt64 в формате переменной длины (base128) NOTE Only up to 2^63 - 1 are supported.*/
void writeVarUInt(UInt64 x, std::ostream & ostr);
void writeVarUInt(UInt64 x, WriteBuffer & ostr);
char * writeVarUInt(UInt64 x, char * ostr);


/** Прочитать UInt64, записанный в формате переменной длины (base128) */
void readVarUInt(UInt64 & x, std::istream & istr);
void readVarUInt(UInt64 & x, ReadBuffer & istr);
const char * readVarUInt(UInt64 & x, const char * istr, size_t size);


/** Получить длину UInt64 в формате VarUInt */
size_t getLengthOfVarUInt(UInt64 x);

/** Получить длину Int64 в формате VarInt */
size_t getLengthOfVarInt(Int64 x);


/** Записать Int64 в формате переменной длины (base128) */
template <typename OUT>
inline void writeVarInt(Int64 x, OUT & ostr)
{
	writeVarUInt(static_cast<UInt64>((x << 1) ^ (x >> 63)), ostr);
}

inline char * writeVarInt(Int64 x, char * ostr)
{
	return writeVarUInt(static_cast<UInt64>((x << 1) ^ (x >> 63)), ostr);
}


/** Прочитать Int64, записанный в формате переменной длины (base128) */
template <typename IN>
inline void readVarInt(Int64 & x, IN & istr)
{
	readVarUInt(*reinterpret_cast<UInt64*>(&x), istr);
	x = (static_cast<UInt64>(x) >> 1) ^ -(x & 1);
}

inline const char * readVarInt(Int64 & x, const char * istr, size_t size)
{
	const char * res = readVarUInt(*reinterpret_cast<UInt64*>(&x), istr, size);
	x = (static_cast<UInt64>(x) >> 1) ^ -(x & 1);
	return res;
}


inline void writeVarT(UInt64 x, std::ostream & ostr) { writeVarUInt(x, ostr); }
inline void writeVarT(Int64 x, std::ostream & ostr) { writeVarInt(x, ostr); }
inline void writeVarT(UInt64 x, WriteBuffer & ostr) { writeVarUInt(x, ostr); }
inline void writeVarT(Int64 x, WriteBuffer & ostr) { writeVarInt(x, ostr); }
inline char * writeVarT(UInt64 x, char * & ostr) { return writeVarUInt(x, ostr); }
inline char * writeVarT(Int64 x, char * & ostr) { return writeVarInt(x, ostr); }

inline void readVarT(UInt64 & x, std::istream & istr) { readVarUInt(x, istr); }
inline void readVarT(Int64 & x, std::istream & istr) { readVarInt(x, istr); }
inline void readVarT(UInt64 & x, ReadBuffer & istr) { readVarUInt(x, istr); }
inline void readVarT(Int64 & x, ReadBuffer & istr) { readVarInt(x, istr); }
inline const char * readVarT(UInt64 & x, const char * istr, size_t size) { return readVarUInt(x, istr, size); }
inline const char * readVarT(Int64 & x, const char * istr, size_t size) { return readVarInt(x, istr, size); }


/// Для [U]Int32, [U]Int16.

inline void readVarUInt(UInt32 & x, ReadBuffer & istr)
{
	UInt64 tmp;
	readVarUInt(tmp, istr);
	x = tmp;
}

inline void readVarInt(Int32 & x, ReadBuffer & istr)
{
	Int64 tmp;
	readVarInt(tmp, istr);
	x = tmp;
}

inline void readVarUInt(UInt16 & x, ReadBuffer & istr)
{
	UInt64 tmp;
	readVarUInt(tmp, istr);
	x = tmp;
}

inline void readVarInt(Int16 & x, ReadBuffer & istr)
{
	Int64 tmp;
	readVarInt(tmp, istr);
	x = tmp;
}


inline void throwReadAfterEOF()
{
	throw Exception("Attempt to read after eof", ErrorCodes::ATTEMPT_TO_READ_AFTER_EOF);
}

inline void readVarUInt(UInt64 & x, ReadBuffer & istr)
{
	x = 0;
	for (size_t i = 0; i < 9; ++i)
	{
		if (istr.eof())
			throwReadAfterEOF();

		uint64_t byte = *istr.position();
		++istr.position();
		x |= (byte & 0x7F) << (7 * i);

		if (!(byte & 0x80))
			return;
	}
}


inline void readVarUInt(UInt64 & x, std::istream & istr)
{
	x = 0;
	for (size_t i = 0; i < 9; ++i)
	{
		uint64_t byte = istr.get();
		x |= (byte & 0x7F) << (7 * i);

		if (!(byte & 0x80))
			return;
	}
}

inline const char * readVarUInt(UInt64 & x, const char * istr, size_t size)
{
	const char * end = istr + size;

	x = 0;
	for (size_t i = 0; i < 9; ++i)
	{
		if (istr == end)
			throwReadAfterEOF();

		uint64_t byte = *istr;
		++istr;
		x |= (byte & 0x7F) << (7 * i);

		if (!(byte & 0x80))
			return istr;
	}

	return istr;
}


inline void writeVarUInt(UInt64 x, WriteBuffer & ostr)
{
	for (size_t i = 0; i < 9; ++i)
	{
		uint8_t byte = x & 0x7F;
		if (x > 0x7F)
			byte |= 0x80;

		ostr.nextIfAtEnd();
		*ostr.position() = byte;
		++ostr.position();

		x >>= 7;
		if (!x)
			return;
	}
}


inline void writeVarUInt(UInt64 x, std::ostream & ostr)
{
	for (size_t i = 0; i < 9; ++i)
	{
		uint8_t byte = x & 0x7F;
		if (x > 0x7F)
			byte |= 0x80;

		ostr.put(byte);

		x >>= 7;
		if (!x)
			return;
	}
}


inline char * writeVarUInt(UInt64 x, char * ostr)
{
	for (size_t i = 0; i < 9; ++i)
	{
		uint8_t byte = x & 0x7F;
		if (x > 0x7F)
			byte |= 0x80;

		*ostr = byte;
		++ostr;

		x >>= 7;
		if (!x)
			return ostr;
	}

	return ostr;
}


inline size_t getLengthOfVarUInt(UInt64 x)
{
	return x < (1ULL << 7) ? 1
		: (x < (1ULL << 14) ? 2
		: (x < (1ULL << 21) ? 3
		: (x < (1ULL << 28) ? 4
		: (x < (1ULL << 35) ? 5
		: (x < (1ULL << 42) ? 6
		: (x < (1ULL << 49) ? 7
		: (x < (1ULL << 56) ? 8
		: 9)))))));
}


inline size_t getLengthOfVarInt(Int64 x)
{
	return getLengthOfVarUInt(static_cast<UInt64>((x << 1) ^ (x >> 63)));
}

}