protobuf

.proto Type	Notes	C++ Type	Java Type	Python Type[2]	Go Type	Ruby Type	C# Type	PHP Type	Dart Type
double		double	double	float	float64	Float	double	float	double
float		float	float	float	float32	Float	float	float	double
int32	Uses variable-length encoding. Inefficient for encoding negative numbers – if your field is likely to have negative values, use sint32 instead.	int32	int	int	int32	Fixnum or Bignum (as required)	int	integer	int
int64	Uses variable-length encoding. Inefficient for encoding negative numbers – if your field is likely to have negative values, use sint64 instead.	int64	long	int/long[3]	int64	Bignum	long	integer/string[5]	Int64
uint32	Uses variable-length encoding.	uint32	int[1]	int/long[3]	uint32	Fixnum or Bignum (as required)	uint	integer	int
uint64	Uses variable-length encoding.	uint64	long[1]	int/long[3]	uint64	Bignum	ulong	integer/string[5]	Int64
sint32	Uses variable-length encoding. Signed int value. These more efficiently encode negative numbers than regular int32s.	int32	int	int	int32	Fixnum or Bignum (as required)	int	integer	int
sint64	Uses variable-length encoding. Signed int value. These more efficiently encode negative numbers than regular int64s.	int64	long	int/long[3]	int64	Bignum	long	integer/string[5]	Int64
fixed32	Always four bytes. More efficient than uint32 if values are often greater than 228.	uint32	int[1]	int/long[3]	uint32	Fixnum or Bignum (as required)	uint	integer	int
fixed64	Always eight bytes. More efficient than uint64 if values are often greater than 256.	uint64	long[1]	int/long[3]	uint64	Bignum	ulong	integer/string[5]	Int64
sfixed32	Always four bytes.	int32	int	int	int32	Fixnum or Bignum (as required)	int	integer	int
sfixed64	Always eight bytes.	int64	long	int/long[3]	int64	Bignum	long	integer/string[5]	Int64
bool		bool	boolean	bool	bool	TrueClass/FalseClass	bool	boolean	bool
string	A string must always contain UTF-8 encoded or 7-bit ASCII text, and cannot be longer than 232.	string	String	str/unicode[4]	string	String (UTF-8)	string	string	String
bytes	May contain any arbitrary sequence of bytes no longer than 232.	string	ByteString	str	[]byte	String (ASCII-8BIT)	ByteString	string	List

https://developers.google.com/protocol-buffers/docs/proto3

https://zhuanlan.zhihu.com/p/341389655