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49 lines
1.3 KiB
Python
49 lines
1.3 KiB
Python
'''
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This module provides classes and functions for handling APDU (Application
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Protocol Data Unit) responses and encoding data in LV (Length-Value) format.
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'''
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from dataclasses import dataclass
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@dataclass
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class APDUResponse:
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'''
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Represents a response to an APDU (Application Protocol Data Unit) command.
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Attributes:
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data (bytes): The response data returned from the APDU command.
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status_word (int): The status word indicating the result of the APDU
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command.
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'''
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data: bytes
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status_word: int
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def __str__(self) -> str:
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return (
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f'APDUResponse(data={bytes(self.data).hex()}, '
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f'status_word={hex(self.status_word)})'
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)
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def encode_lv(value: bytes) -> bytes:
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'''
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Encodes the given bytes using LV (Length-Value) encoding.
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The function prepends the length of the input bytes as a single byte,
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followed by the value itself. The maximum supported length is 255 bytes.
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Args:
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value (bytes): The data to encode.
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Returns:
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bytes: The LV-encoded bytes.
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Raises:
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ValueError: If the input exceeds 255 bytes in length.
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'''
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if len(value) > 255:
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raise ValueError('LV encoding supports up to 255 bytes')
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return bytes([len(value)]) + value
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