Coverage for src/bluetooth_sig/gatt/descriptors/characteristic_aggregate_format.py: 85%

1"""Characteristic Aggregate Format Descriptor implementation.""" 

2 

3from __future__ import annotations 

4 

5import msgspec 

6 

7from ..characteristics.utils import DataParser 

8from .base import BaseDescriptor 

9 

10 

11class CharacteristicAggregateFormatData(msgspec.Struct, frozen=True, kw_only=True): 

12 """Characteristic Aggregate Format descriptor data.""" 

13 

14 attribute_handles: list[int] 

15 

16 

17class CharacteristicAggregateFormatDescriptor(BaseDescriptor): 

18 """Characteristic Aggregate Format Descriptor (0x2905). 

19 

20 Contains a list of attribute handles that collectively form an aggregate value. 

21 Used to group multiple characteristics into a single logical value. 

22 """ 

23 

24 def _has_structured_data(self) -> bool: 

25 return True 

26 

27 def _get_data_format(self) -> str: 

28 return "uint16[]" 

29 

30 def _parse_descriptor_value(self, data: bytes) -> CharacteristicAggregateFormatData: 

31 """Parse Characteristic Aggregate Format value. 

32 

33 Contains a list of 16-bit attribute handles (little-endian). 

34 The number of handles is determined by data length / 2. 

35 

36 Args: 

37 data: Raw bytes containing attribute handles 

38 

39 Returns: 

40 CharacteristicAggregateFormatData with list of handles 

41 

42 Raises: 

43 ValueError: If data length is not even (handles are 2 bytes each) 

44 """ 

45 if len(data) % 2 != 0: 

46 raise ValueError(f"Characteristic Aggregate Format data must have even length, got {len(data)}") 

47 

48 if len(data) == 0: 

49 return CharacteristicAggregateFormatData(attribute_handles=[]) 

50 

51 handles: list[int] = [] 

52 for i in range(0, len(data), 2): 

53 handle = DataParser.parse_int16(data, offset=i, endian="little") 

54 handles.append(handle) 

55 

56 return CharacteristicAggregateFormatData(attribute_handles=handles) 

57 

58 def get_attribute_handles(self, data: bytes) -> list[int]: 

59 """Get the list of attribute handles.""" 

60 parsed = self._parse_descriptor_value(data) 

61 return parsed.attribute_handles 

62 

63 def get_handle_count(self, data: bytes) -> int: 

64 """Get the number of attribute handles.""" 

65 return len(self.get_attribute_handles(data))