Remove unnecessary special handling of large fields

Ref. #531

rflx/pyrflx/typevalue.py

@@ -709,25 +709,11 @@ def set_field_without_size(field_name: str, field: MessageValue.Field) -> Tuple[
         def set_field_with_size(field_name: str, field_size: int) -> Tuple[int, int]:
             assert isinstance(value, Bitstring)
             last_pos_in_bitstr = current_pos_in_bitstring = get_current_pos_in_bitstr(field_name)
-            if field_size < 8 or field_size % 8 == 0:
-                self.set(
-                    field_name,
-                    value[current_pos_in_bitstring : current_pos_in_bitstring + field_size],
-                )
-                current_pos_in_bitstring += field_size
-            else:
-                bytes_used_for_field = field_size // 8 + 1
-                first_pos = current_pos_in_bitstring
-                field_bits = Bitstring()
-
-                for _ in range(bytes_used_for_field - 1):
-                    field_bits += value[current_pos_in_bitstring : current_pos_in_bitstring + 8]
-                    current_pos_in_bitstring += 8
-
-                k = field_size // bytes_used_for_field + 1
-                field_bits += value[current_pos_in_bitstring + 8 - k : first_pos + field_size]
-                current_pos_in_bitstring = first_pos + field_size
-                self.set(field_name, field_bits)
+            self.set(
+                field_name,
+                value[current_pos_in_bitstring : current_pos_in_bitstring + field_size],
+            )
+            current_pos_in_bitstring += field_size
             return last_pos_in_bitstr, current_pos_in_bitstring
 
         while current_field_name != FINAL.name:

tests/data/specs/unaligned_field.rflx

@@ -0,0 +1,12 @@
+package Unaligned_Field is
+
+   type T1 is mod 2**7;
+   type T2 is mod 2**18;
+
+   type M1 is
+      message
+         F1 : T1;
+         F2 : T1;
+         F3 : T2;
+      end message;
+end Unaligned_Field;

tests/unit/pyrflx_test.py

@@ -1077,3 +1077,21 @@ def msg_checksum(_: bytes, **__: object) -> int:
     tlv_message = message.get("Payload")
     assert isinstance(tlv_message, MessageValue)
     assert tlv_message.valid_message
+
+
+@pytest.mark.parametrize(
+    "data, f1, f2, f3",
+    [
+        (b"\x00\x00\x00\x00", 0, 0, 0),
+        (b"\x11\x11\x11\x11", 0x8, 0x44, 0x11111),
+        (b"\x11\x22\x33\x44", 0x8, 0x48, 0x23344),
+        (b"\xff\xff\xff\xff", 0x7F, 0x7F, 0x3FFFF),
+    ],
+)
+def test_unaligned_field_serialization(data: bytes, f1: int, f2: int, f3: int) -> None:
+    msg = PyRFLX.from_specs([f"{SPEC_DIR}/unaligned_field.rflx"])["Unaligned_Field"]["M1"]
+    msg.parse(data)
+    assert msg.get("F1") == f1
+    assert msg.get("F2") == f2
+    assert msg.get("F3") == f3
+    assert data == msg.bytestring