Protocol Data Types

This page defines the fundamental data types used in the MariaDB client/server protocol, including integers, strings, and binary representations.

List of Possible Types

Unknown type:

byte<1>	Fixed-length bytes
byte	Length-encoded bytes
byte	End-of-file length bytes

Integer type:

int<1>	Fixed-length integers
int	Length-encoded integers

String type:

string	Fixed-length strings
string	Null-terminated strings
string	Length-encoded strings
string	End-of-file length strings

Fixed length bytes

The notation is "byte".

A fixed-length byte stores the value in a series of n bytes.

Length encoded bytes

The notation is "byte".

Length encoded bytes are prefixed by a length-encoded integer which describes the length of the byte value, followed by the bytes value.

End of file length bytes

The notation is "byte".

Bytes whose length will be calculated by the packet remaining length.

Fixed length integers

Notation is "int".

A fixed-length integer stores the value in a series of n bytes. The least significant byte is always the first byte (little-endian format).

Example

An int<4> with value 2 is stored as02 00 00 00

Length encoded integers

The notation is "int".

An integer which depending on its value is represented by n bytes.

The first byte represents the size of the integer:

If the value of first byte is

• < 0xFB - Integer value is this 1 byte integer

• 0xFB - NULL value

• 0xFC - Integer value is encoded in the next 2 bytes (3 bytes total)

• 0xFD - Integer value is encoded in the next 3 bytes (4 bytes total)

• 0xFE - Integer value is encoded in the next 8 bytes (9 bytes total)

Fixed-length strings

The notation is "string".

Fixed-length strings have a known hardcoded length.

Null-terminated strings

The notation is "string".

Null-terminated strings have a variable size and are terminated by a 0x00 character

Length-encoded strings

The notation is "string".

Length-encoded strings are prefixed by a length-encoded integer which describes the length of the string, followed by the string value.

Example

An string of 512 "a" is encoded in 515 bytes :

fc 00 02 97 97 97 97 97 97 97 97 97 97 97 97 97	² .. a a a a a a a a a a a a a

... The NULL value is encoded using null (0xfb) length.

An empty value is encoded with a 0 (0x00) length.

End of File Length Strings

The notation is "string".

Strings whose length is calculated by the packet remaining length.

For an example, see the COM_STMT_PREPARE packet.

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