fix: marshall multi-byte strings correctly (#261)

src/dbus_fast/_private/marshaller.py

@@ -68,7 +68,7 @@ class Marshaller:
 
     def _write_string(self, value: _str) -> int:
         value_bytes = value.encode()
-        value_len = len(value)
+        value_len = len(value_bytes)
         written = self._align(4) + 4
         buf = self._buf
         buf += PACK_UINT32(value_len)

tests/data/messages.json

@@ -242,5 +242,17 @@
       "body": [["hello", "worl"], true, false, ["hello", "worl"], true, false]
     },
     "data": "6c01000148000000010000007e00000001016f00150000002f6f72672f667265656465736b746f702f4442757300000002017300140000006f72672e667265656465736b746f702e4442757300000000030173000500000048656c6c6f00000006017300140000006f72672e667265656465736b746f702e444275730000000008016700086173626261736262000000150000000500000068656c6c6f00000004000000776f726c000000000100000000000000150000000500000068656c6c6f00000004000000776f726c000000000100000000000000"
+  },
+  {
+    "message": {
+      "destination": "org.freedesktop.DBus",
+      "path": "/org/freedesktop/DBus",
+      "interface": "org.freedesktop.DBus",
+      "member": "Hello",
+      "serial": 1,
+      "signature": "as",
+      "body": [["//doesntmatter/über"]]
+    },
+    "data": "6c0100011d000000010000007800000001016f00150000002f6f72672f667265656465736b746f702f4442757300000002017300140000006f72672e667265656465736b746f702e4442757300000000030173000500000048656c6c6f00000006017300140000006f72672e667265656465736b746f702e4442757300000000080167000261730019000000140000002f2f646f65736e746d61747465722fc3bc62657200"
   }
 ]

tests/test_marshaller.py

@@ -678,3 +678,39 @@ def test_unmarshall_mount_message_2():
         ],
         [],
     ]
+
+
+def test_unmarshall_multi_byte_string():
+    """Test unmarshall a multi-byte string."""
+
+    mount_message = (
+        b"l\x01\x00\x01\x1d\x00\x00\x00"
+        b"\x01\x00\x00\x00x\x00\x00\x00"
+        b"\x01\x01o\x00\x15\x00\x00\x00"
+        b"/org/fre"
+        b"edesktop"
+        b"/DBus\x00\x00\x00"
+        b"\x02\x01s\x00\x14\x00\x00\x00"
+        b"org.free"
+        b"desktop."
+        b"DBus\x00\x00\x00\x00"
+        b"\x03\x01s\x00\x05\x00\x00\x00"
+        b"Hello\x00\x00\x00"
+        b"\x06\x01s\x00\x14\x00\x00\x00"
+        b"org.free"
+        b"desktop."
+        b"DBus\x00\x00\x00\x00"
+        b"\x08\x01g\x00\x02as\x00"
+        b"\x19\x00\x00\x00\x14\x00\x00\x00"
+        b"//doesnt"
+        b"matter/\xc3"
+        b"\xbcber\x00"
+    )
+
+    stream = io.BytesIO(mount_message)
+    unmarshaller = Unmarshaller(stream)
+    unmarshaller.unmarshall()
+    message = unmarshaller.message
+    assert unmarshaller.message.signature == "as"
+    unpacked = unpack_variants(message.body)
+    assert unpacked == [["//doesntmatter/über"]]