Follow-up octet-stream codec - short explanation #1194 (#1209)

* docs: add `octet-stream` codec documentation

* fix: statisfy prettier

* fix: adjust bit offset

Co-authored-by: danielpeintner <daniel.peintner@gmail.com>

---------

Co-authored-by: danielpeintner <daniel.peintner@gmail.com>

Author: derwehr

packages/core/README.md

@@ -21,6 +21,40 @@ see binding examples such as
 -   https://github.com/eclipse-thingweb/node-wot/blob/master/packages/binding-http
 -   https://github.com/eclipse-thingweb/node-wot/blob/master/packages/binding-coap
 
+## Codecs
+
+### Octet-Stream
+
+The octet-stream codec enables deserialization and serialization of binary data. To encode and decode sequences of bytes, the octet-stream codec uses the following content type parameters:
+| Parameter | Description | Default |
+| --- | --- | --- |
+| `length` | Number of bytes produced during serialization or consumed during deserialization | |
+| `signed` | Signedness of the data type, `true` or `false` | `true` |
+| `byteSeq` | Endianness, enum of `BIG_ENDIAN`, `LITTLE_ENDIAN`, `BIG_ENDIAN_BYTE_SWAP`, `LITTLE_ENDIAN_BYTE_SWAP` | `BIG_ENDIAN` |
+
+Additionally, the octet-stream codec supports the data schema terms below for addressing bit-fields:
+| Term | Description | Default |
+| --- | --- | --- |
+| `ex:bitLength` | Number of bits produced during serialization or consumed during deserialization | |
+| `ex:bitOffset` | Offset in bits from the beginning of the byte sequence | `0` |
+
+With the help of the terms and parameters above, the octet-stream codec can be used to serialize and deserialize objects containing bit-fields and sequences of bytes, like in the following example.
+
+#### Example
+
+To serialize the object `{ flag1: true, numberProperty: 99, stringProperty: "Web" }` to a sequence of bytes, the content type `application/octet-stream;length=4;signed=false;`, along with the following data schema can be used:
+
+```json
+{
+    "type": "object",
+    "properties": {
+        "flag1": { "type": "boolean", "ex:bitOffset": 0, "ex:bitLength": 1 },
+        "numberProperty": { "type": "integer", "ex:bitOffset": 1, "ex:bitLength": 7 },
+        "stringProperty": { "type": "string", "ex:bitOffset": 8, "ex:bitLength": 24 }
+    }
+}
+```
+
 ## More Details
 
 See <https://github.com/eclipse-thingweb/node-wot/>