Project

General

Profile

Htsmsgbinary » History » Version 1

Andreas Smas, 2010-12-08 21:37

1 1 Andreas Smas
= Message structure =
2
3
A message can be of either 'map' or 'list' type. In a map each field has a name, in a list the members do not have names but the order should be preserved.
4
5
The field types are:
6
7
||Name||ID||Description
8
||Map||1||Sub message of type map
9
||S64||2||Signed 64bit integer
10
||Str||3||UTF-8 encoded string
11
||Bin||4||Binary blob
12
||List||5||Sub message of type list
13
14
All in all the message structure is quite similar to JSON but most notably; no boolean nor null type exist and HTSMSG supports binary objects.
15
16
= HTSMSG binary format =
17
18
The binary format is designed to for back-to-back transmission of messages over a network (TCP) connection.
19
20
The root message must always be of type map.
21
22
== Root body ==
23
24
 ||Length||4 byte integer||Total length of message (including this length field itself)
25
 ||Body||HTSMSG-Field * N||Fields in the root body
26
27
== HTSMSG-Field ==
28
29
 ||Type||1 byte integer||Type of field (see field type IDs above)
30
 ||Namelength||1 byte integer||Length of name of field. If a field is part of a list message this must be 0
31
 ||Datalength||4 byte integer||Length of field data
32
 ||Name||N bytes||Field name, length as specified by Namelength
33
 ||Data||N bytes||Field payload, for details see below
34
35
=== Field encoding for type: map and list ===
36
37
The data is repeated HTSMSG-Fields exactly as the root body. Note the subtle difference in that for the root-message the length includes the 4 bytes of length field itself whereas in the field encoding the length written includes just the actual payload.
38
39
=== Field encoding for type: s64 ===
40
41
Integers are encoded using a very simple variable length encoding. All leading bytes that are 0 is discarded. So to encode the value 100, datalength should be 1 and the data itself should be just one byte [0x64]. To encode 1337; datalength=2, data=[0x05 0x39].
42
43
Note that there is no sign extension in this encoding scheme so if you need to encode -1 you need to set datalength=8 and data = [0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff]. This can certainly be thought of as a bug, but it is the way it is.
44
45
=== Field encoding for type: str ===
46
47
Datalength should be the length of the string (NOT including the null terminating character). Thus the null terminator should not be present in data either.
48
49
=== Field encoding for type: bin ===
50
51
Datalength should be the length of the binary object. Data is the binary object itself.
52
53