Htsmsgbinary » History » Version 3
Andreas Smas, 2010-12-08 21:38
1 | 1 | Andreas Smas | |
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2 | 3 | Andreas Smas | h1. Message structure |
3 | 1 | Andreas Smas | |
4 | 3 | Andreas Smas | |
5 | 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. |
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7 | 1 | Andreas Smas | The field types are: |
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9 | ||Name||ID||Description |
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10 | ||Map||1||Sub message of type map |
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11 | ||S64||2||Signed 64bit integer |
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12 | ||Str||3||UTF-8 encoded string |
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13 | ||Bin||4||Binary blob |
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14 | ||List||5||Sub message of type list |
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16 | 3 | Andreas Smas | 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. |
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19 | 3 | Andreas Smas | h1. HTSMSG binary format |
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22 | 1 | Andreas Smas | The binary format is designed to for back-to-back transmission of messages over a network (TCP) connection. |
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24 | 3 | Andreas Smas | The root message must always be of type *map*. |
25 | 2 | Andreas Smas | |
26 | 1 | Andreas Smas | |
27 | 3 | Andreas Smas | h2. Root body |
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30 | 1 | Andreas Smas | ||Length||4 byte integer||Total length of message (including this length field itself) |
31 | ||Body||HTSMSG-Field * N||Fields in the root body |
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34 | 3 | Andreas Smas | h2. HTSMSG-Field |
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37 | 1 | Andreas Smas | ||Type||1 byte integer||Type of field (see field type IDs above) |
38 | ||Namelength||1 byte integer||Length of name of field. If a field is part of a list message this must be 0 |
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39 | ||Datalength||4 byte integer||Length of field data |
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40 | ||Name||N bytes||Field name, length as specified by Namelength |
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41 | ||Data||N bytes||Field payload, for details see below |
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44 | 3 | Andreas Smas | h3. Field encoding for type: map and list |
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47 | 1 | Andreas Smas | 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. |
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50 | 3 | Andreas Smas | h3. Field encoding for type: s64 |
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53 | 1 | Andreas Smas | 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]. |
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55 | 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. |
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58 | 3 | Andreas Smas | h3. Field encoding for type: str |
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61 | 1 | Andreas Smas | 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. |
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63 | 3 | Andreas Smas | |
64 | h3. Field encoding for type: bin |
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66 | 1 | Andreas Smas | |
67 | Datalength should be the length of the binary object. Data is the binary object itself. |
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69 |