Add support for encoding a TLV string

python_otbr_api/tlv_parser.py

@@ -2,6 +2,7 @@
 from __future__ import annotations
 
 from enum import IntEnum
+import struct
 
 
 class TLVError(Exception):
@@ -53,6 +54,30 @@ class MeshcopTLVType(IntEnum):
     JOINERADVERTISEMENT = 241
 
 
+def _encode_item(tag: MeshcopTLVType, data: str) -> bytes:
+    """Encode a dataset item to TLV format."""
+    if tag == MeshcopTLVType.NETWORKNAME:
+        data_bytes = bytes(data, "utf-8")
+    else:
+        data_bytes = bytes.fromhex(data)
+
+    data_len = len(data_bytes)
+    return struct.pack(f"!BB{data_len}s", tag, data_len, data_bytes)
+
+
+def encode_tlv(items: dict[MeshcopTLVType, str]) -> str:
+    """Encode a TLV encoded dataset to a hex string.
+
+    Raises if the TLV is invalid.
+    """
+    result = b""
+
+    for item_type, item in items.items():
+        result += _encode_item(item_type, item)
+
+    return result.hex()
+
+
 def _parse_item(tag: MeshcopTLVType, data: bytes) -> str:
     """Parse a TLV encoded dataset item."""
     if tag == MeshcopTLVType.NETWORKNAME:

tests/test_tlv_parser.py

@@ -2,7 +2,32 @@
 
 import pytest
 
-from python_otbr_api.tlv_parser import MeshcopTLVType, TLVError, parse_tlv
+from python_otbr_api.tlv_parser import MeshcopTLVType, TLVError, encode_tlv, parse_tlv
+
+
+def test_encode_tlv() -> None:
+    """Test the TLV parser."""
+    dataset = {
+        MeshcopTLVType.ACTIVETIMESTAMP: "0000000000010000",
+        MeshcopTLVType.CHANNEL: "00000f",
+        MeshcopTLVType.CHANNELMASK: "0004001fffe0",
+        MeshcopTLVType.EXTPANID: "1111111122222222",
+        MeshcopTLVType.MESHLOCALPREFIX: "fdad70bfe5aa15dd",
+        MeshcopTLVType.NETWORKKEY: "00112233445566778899aabbccddeeff",
+        MeshcopTLVType.NETWORKNAME: "OpenThreadDemo",
+        MeshcopTLVType.PANID: "1234",
+        MeshcopTLVType.PSKC: "445f2b5ca6f2a93a55ce570a70efeecb",
+        MeshcopTLVType.SECURITYPOLICY: "02a0f7f8",
+    }
+    dataset_tlv = encode_tlv(dataset)
+    assert (
+        dataset_tlv
+        == (
+            "0E080000000000010000000300000F35060004001FFFE0020811111111222222220708FDAD"
+            "70BFE5AA15DD051000112233445566778899AABBCCDDEEFF030E4F70656E54687265616444"
+            "656D6F010212340410445F2B5CA6F2A93A55CE570A70EFEECB0C0402A0F7F8"
+        ).lower()
+    )
 
 
 def test_parse_tlv() -> None: