Protocol data types

List of possible types

Unknown type:

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

Integer type:

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

String type:

string<fix>Fixed-length strings
string<NUL>Null-terminated strings
string<lenenc>Length-encoded strings
string<EOF>End-of-file length strings


Fixed length bytes

The notation is "byte<n>"

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



Length encoded bytes

The notation is "byte<lenenc>" 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<EOF>" Bytes whose length will be calculated by the packet remaining length.

Fixed length integers

Notation is "int<n>"

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 as 02 00 00 00

Length encoded integers

The notation is "int<lenenc>" 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<fix>" Fixed-length strings have a known hardcoded length.

Null-terminated strings

The notation is "string<NUL>" Null-terminated strings have a variable size and are terminated by a 0x00 character

Length-encoded strings

The notation is "string<lenenc>" 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" will be encoded in 515 bytes :

fc 00 02 97 97 97 97 97 97 97 97 97 97 97 97 97² .. a a a a a a a a a a a a a

...



End of file length strings

The notation is "string<EOF>" Strings whose length will be calculated by the packet remaining length. For an example see COM_STMT_PREPARE packet.

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