google protobuf

Posted 2020-07-30 RushoutAsia

Specifying Field Rules

You specify that message fields are one of the following:

• required: a well-formed message must have exactly one of this field.
• optional: a well-formed message can have zero or one of this field (but not more than one).
• repeated: this field can be repeated any number of times (including zero) in a well-formed message. The order of the repeated values will be preserved.

Scalar Value Types

A scalar message field can have one of the following types – the table shows the type specified in the .proto file, and the corresponding type in the automatically generated class:

.proto Type	Notes	C++ Type	Java Type	Python Type[2]	Go Type
double		double	double	float	*float64
float		float	float	float	*float32
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
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
uint32	Uses variable-length encoding.	uint32	int[1]	int/long[3]	*uint32
uint64	Uses variable-length encoding.	uint64	long[1]	int/long[3]	*uint64
sint32	Uses variable-length encoding. Signed int value. These more efficiently encode negative numbers than regular int32s.	int32	int	int	*int32
sint64	Uses variable-length encoding. Signed int value. These more efficiently encode negative numbers than regular int64s.	int64	long	int/long[3]	*int64
fixed32	Always four bytes. More efficient than uint32 if values are often greater than 228.	uint32	int[1]	int	*uint32
fixed64	Always eight bytes. More efficient than uint64 if values are often greater than 256.	uint64	long[1]	int/long[3]	*uint64
sfixed32	Always four bytes.	int32	int	int	*int32
sfixed64	Always eight bytes.	int64	long	int/long[3]	*int64
bool		bool	boolean	bool	*bool
string	A string must always contain UTF-8 encoded or 7-bit ASCII text.	string	String	str/unicode[4]	*string
bytes	May contain any arbitrary sequence of bytes.	string	ByteString	str	[]byte