dalet/specification/daletpack.md

DaletPack specification for Dalet v1.0-preview

DaletPack is an binary data format for Dalet, that is used for minimizing the size of transmitted daletl data. DaletPack is designed specifically to transfer as little data as possible, it compresses the declaration of tag types into the smallest possible volume. Nothing unnecessary is transferred.

All data must be compressed in Zstandard format.

Root data format is array of tags (see Daletl specification), each element reads sequentially without type and size definition.

Types (16)

• Null
• Integer
• String (6)
• Array (5)
• Tags (3)
  • Tag only with id
  • Tag with id and body
  • Tag with id, body and argument

Limitations

• a value of integer (4 bits) must be between 0 and 15
• maximum byte size of a String object is (2^32)-1
• string must be encoded in UTF-8
• maximum number of elements of an Array object is (2^32)-1

Formats

Overview

name	id	id-bits
null	0	0000
int	1	0001
str 3	2	0010
str 4	3	0011
str 8	4	0100
str 16	5	0101
str 32	6	0110
arr 3	7	0111
arr 4	8	1000
arr 8	9	1001
arr 16	10	1010
arr 32	11	1011
tag (id)	12	1100
tag (id, body)	13	1101
tag (id, argument)	14	1110
tag (id, body, argument)	15	1111

Notation in diagrams

block of bits (max 8 bits):
+--------+
|        |
+--------+

a variable number of bytes:
+========+
|        |
+========+

variable number of objects stored in DaletPack format:
+~~~~~~~~~~~~~~~~~+
|                 |
+~~~~~~~~~~~~~~~~~+

Null format

+--------+
|  0000  |
+--------+

Integer format

+--------+------+
|  0001  | XXXX |
+--------+------+

String format

str 3 (up to 7 bytes):
+--------+-----+========+
|  0010  | XXX |  data  |
+--------+-----+========+

str 4 (up to 15 bytes):
+--------+------+========+
|  0011  | XXXX |  data  |
+--------+------+========+

str 8 (up to 255 bytes):
+--------+----------+========+
|  0100  | XXXXXXXX |  data  |
+--------+----------+========+

str 16 (up to 2^16-1 bytes):
+--------+----------+----------+========+
|  0101  | XXXXXXXX | XXXXXXXX |  data  |
+--------+----------+----------+========+

str 32 (up to 2^32-1 bytes):
+--------+----------+----------+----------+----------+========+
|  0110  | XXXXXXXX | XXXXXXXX | XXXXXXXX | XXXXXXXX |  data  |
+--------+----------+----------+----------+----------+========+

Array format

arr 3 (up to 7 elements):
+--------+-----+~~~~~~~~+
|  0111  | XXX |  data  |
+--------+-----+~~~~~~~~+

arr 4 (up to 15 elements):
+--------+------+~~~~~~~~+
|  1000  | XXXX |  data  |
+--------+------+~~~~~~~~+

arr 8 (up to 255 elements):
+--------+----------+~~~~~~~~+
|  1001  | XXXXXXXX |  data  |
+--------+----------+~~~~~~~~+

arr 16 (up to 2^16-1 elements):
+--------+----------+----------+~~~~~~~~+
|  1010  | XXXXXXXX | XXXXXXXX |  data  |
+--------+----------+----------+~~~~~~~~+

arr 32 (up to 2^32-1 elements):
+--------+----------+----------+----------+----------+~~~~~~~~+
|  1011  | XXXXXXXX | XXXXXXXX | XXXXXXXX | XXXXXXXX |  data  |
+--------+----------+----------+----------+----------+~~~~~~~~+

Tag format

Y = tag_id = XXXXX (5 bits) (can change before release)

tag (id):
+--------+---+
|  1100  | Y |
+--------+---+

tag (id, body):
+--------+---+~~~~~~~~+
|  1101  | Y |  body  |
+--------+---+~~~~~~~~+

tag (id, argument):
+--------+---+~~~~~~~~~~~~+
|  1101  | Y |  argument  |
+--------+---+~~~~~~~~~~~~+

tag (id, body, argument):
+--------+---+~~~~~~~~+~~~~~~~~~~~~+
|  1111  | Y |  data  |  argument  |
+--------+---+~~~~~~~~+~~~~~~~~~~~~+