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Created July 9, 2012 22:59
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MessagePack Format Specification
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msgpack_spec.md

Fixnums

positive fixnum

Save an integer within the range [0, 127] in 1 bytes.

+--------+
|0XXXXXXX|
+--------+
=> unsigned 8-bit 0XXXXXXX

negative fixnum

Save an integer within the range [-32, -1] in 1 bytes.

+--------+
|111XXXXX|
+--------+
=> signed 8-bit 111XXXXX

Unsigned Integers

uint 8

Save an unsigned 8-bit integer in 2 bytes.

+--------+--------+
|  0xcc  |XXXXXXXX|
+--------+--------+
=> unsigned 8-bit XXXXXXXX

uint 16

Save an unsigned 16-bit big-endian integer in 3 bytes.

+--------+--------+--------+
|  0xcd  |XXXXXXXX|XXXXXXXX|
+--------+--------+--------+
=> unsigned 16-bit big-endian XXXXXXXX_XXXXXXXX

uint 32

Save an unsigned 32-bit big-endian integer in 5 bytes.

+--------+--------+--------+--------+--------+
|  0xce  |XXXXXXXX|XXXXXXXX|XXXXXXXX|XXXXXXXX|
+--------+--------+--------+--------+--------+
=> unsigned 32-bit big-endian XXXXXXXX_XXXXXXXX_XXXXXXXX_XXXXXXXX

uint 64

Save an unsigned 64-bit big-endian integer in 9 bytes.

+--------+--------+--------+--------+--------+--------+--------+--------+--------+
|  0xcf  |XXXXXXXX|XXXXXXXX|XXXXXXXX|XXXXXXXX|XXXXXXXX|XXXXXXXX|XXXXXXXX|XXXXXXXX|
+--------+--------+--------+--------+--------+--------+--------+--------+--------+
=> unsigned 64-bit big-endian XXXXXXXX_XXXXXXXX_XXXXXXXX_XXXXXXXX_XXXXXXXX_XXXXXXXX_XXXXXXXX_XXXXXXXX

Signed Integers

int 8

Save a signed 8-bit integer in 2 bytes.

+--------+--------+
|  0xd0  |XXXXXXXX|
+--------+--------+
=> signed 8-bit XXXXXXXX

int 16

Save a signed 16-bit big-endian integer in 3 bytes.

+--------+--------+--------+
|  0xd1  |XXXXXXXX|XXXXXXXX|
+--------+--------+--------+
=> signed 16-bit big-endian XXXXXXXX_XXXXXXXX

int 32

Save a signed 32-bit big-endian integer in 5 bytes.

+--------+--------+--------+--------+--------+
|  0xd2  |XXXXXXXX|XXXXXXXX|XXXXXXXX|XXXXXXXX|
+--------+--------+--------+--------+--------+
  => signed 32-bit big-endian XXXXXXXX_XXXXXXXX_XXXXXXXX_XXXXXXXX

int 64

Save a signed 64-bit big-endian integer in 9 bytes.

+--------+--------+--------+--------+--------+--------+--------+--------+--------+
|  0xd3  |XXXXXXXX|XXXXXXXX|XXXXXXXX|XXXXXXXX|XXXXXXXX|XXXXXXXX|XXXXXXXX|XXXXXXXX|
+--------+--------+--------+--------+--------+--------+--------+--------+--------+
=> signed 64-bit big-endian XXXXXXXX_XXXXXXXX_XXXXXXXX_XXXXXXXX_XXXXXXXX_XXXXXXXX_XXXXXXXX_XXXXXXXX

Nil

Save a nil.

+--------+
|  0xc0  |
+--------+

Boolean

true

+--------+
|  0xc3  |
+--------+

false

+--------+
|  0xc2  |
+--------+

Floating point

float

Save a big-endian IEEE 754 single precision floating point number in 5 bytes.

+--------+--------+--------+--------+--------+
|  0xca  |XXXXXXXX|XXXXXXXX|XXXXXXXX|XXXXXXXX|
+--------+--------+--------+--------+--------+
=> big-endian IEEE 754 single precision floating point number XXXXXXXX_XXXXXXXX_XXXXXXXX_XXXXXXXX

double

Save a big-endian IEEE 754 double precision floating point number in 9 bytes.

+--------+--------+--------+--------+--------+--------+--------+--------+--------+
|  0xcb  |XXXXXXXX|XXXXXXXX|XXXXXXXX|XXXXXXXX|XXXXXXXX|XXXXXXXX|XXXXXXXX|XXXXXXXX|
+--------+--------+--------+--------+--------+--------+--------+--------+--------+
=> big-endian IEEE 754 single precision floating point number XXXXXXXX_XXXXXXXX_XXXXXXXX_XXXXXXXX_XXXXXXXX_XXXXXXXX_XXXXXXXX_XXXXXXXX

Raw bytes

fix raw

Save raw bytes up to 31 bytes.

+--------+--------
|101XXXXX|...N bytes
+--------+--------
=> 000XXXXXX (=N) bytes of raw bytes.

raw 16

Save raw bytes up to (2^16)-1 bytes. Length is stored in unsigned 16-bit big-endian integer.

+--------+--------+--------+--------
|  0xda  |XXXXXXXX|XXXXXXXX|...N bytes
+--------+--------+--------+--------
=> XXXXXXXX_XXXXXXXX (=N) bytes of raw bytes.

raw 32

Save raw bytes up to (2^32)-1 bytes. Length is stored in unsigned 32-bit big-endian integer.

+--------+--------+--------+--------+--------+--------
|  0xdb  |XXXXXXXX|XXXXXXXX|XXXXXXXX|XXXXXXXX|...N bytes
+--------+--------+--------+--------+--------+--------
=> XXXXXXXX_XXXXXXXX_XXXXXXXX_XXXXXXXX (=N) bytes of raw bytes.

Arrays

fix array

Save an array up to 15 elements.

+--------+--------
|1001XXXX|...N objects
+--------+--------
=> 0000XXXX (=N) elements array.

array 16

Save an array up to (2^16)-1 elements. Number of elements is stored in unsigned 16-bit big-endian integer.

+--------+--------+--------+--------
|  0xdc  |XXXXXXXX|XXXXXXXX|...N objects
+--------+--------+--------+--------
=> XXXXXXXX_XXXXXXXX (=N) elements array.

array 32

Save an array up to (2^32)-1 bytes. Number of elements is stored in unsigned 32-bit big-endian integer.

+--------+--------+--------+--------+--------+--------
|  0xdd  |XXXXXXXX|XXXXXXXX|XXXXXXXX|XXXXXXXX|...N objects
+--------+--------+--------+--------+--------+--------
=> XXXXXXXX_XXXXXXXX_XXXXXXXX_XXXXXXXX (=N) bytes of raw bytes.

Maps

fix map

Save a map up to 15 elements.

+--------+--------
|1000XXXX|...N*2 objects
+--------+--------
=> 0000XXXX (=N) elements map
   where odd elements are key and next element of the key is its associate value.

map 16

Save a map up to (2^16)-1 elements. Number of elements is stored in unsigned 16-bit big-endian integer.

+--------+--------+--------+--------
|  0xde  |XXXXXXXX|XXXXXXXX|...N*2 objects
+--------+--------+--------+--------
=> XXXXXXXX_XXXXXXXX (=N) elements map
   where odd elements are key and next element of the key is its associate value.

map 32

Save a map up to (2^32)-1 elements. Number of elements is stored in unsigned 32-bit big-endian integer.

+--------+--------+--------+--------+--------+--------
|  0xdf  |XXXXXXXX|XXXXXXXX|XXXXXXXX|XXXXXXXX|...N*2 objects
+--------+--------+--------+--------+--------+--------
=> XXXXXXXX_XXXXXXXX_XXXXXXXX_XXXXXXXX (=N) elements map
   where odd elements are key and next element of the key is its associate value.

Type Chart

Type                Binary      Hex

Positive FixNum     0xxxxxxx    0x00 - 0x7f
FixMap              1000xxxx    0x80 - 0x8f
FixArray            1001xxxx    0x90 - 0x9f
FixRaw              101xxxxx    0xa0 - 0xbf
nil                 11000000    0xc0
reserved            11000001    0xc1
false               11000010    0xc2
true                11000011    0xc3
reserved            11000100    0xc4
reserved            11000101    0xc5
reserved            11000110    0xc6
reserved            11000111    0xc7
reserved            11001000    0xc8
reserved            11001001    0xc9
float               11001010    0xca
double              11001011    0xcb
uint 8              11001100    0xcc
uint 16             11001101    0xcd
uint 32             11001110    0xce
uint 64             11001111    0xcf
int 8               11010000    0xd0
int 16              11010001    0xd1
int 32              11010010    0xd2
int 64              11010011    0xd3
reserved            11010100    0xd4
reserved            11010101    0xd5
reserved            11010110    0xd6
reserved            11010111    0xd7
reserved            11011000    0xd8
reserved            11011001    0xd9
raw 16              11011010    0xda
raw 32              11011011    0xdb
array 16            11011100    0xdc
array 32            11011101    0xdd
map 16              11011110    0xde
map 32              11011111    0xdf
Negative FixNum     111xxxxx    0xe0 - 0xff

Notes

This text is from The Official MsgPack Format Specification and is simply reformatted. If you notice any inconsistencies or changes over time, please leave a comment below and it will be corrected.

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