c486039053
The tests/ directory held 50 laboratory programs and no tests. They model channels, run hundreds of repetitions and write CSV, PNG and reports; calling that a test suite blocked introducing a real one, because any pytest run would have collected the labs and re-executed every experiment. - move all 50 lab programs to experiments/ with git mv, preserving history - rewrite the 38 cross-imports between labs from tests.labNNN to experiments.labNNN - leave tests/ empty for actual fast checks of protocol/ - point quick_gate and the hook at the new layout and add experiments/ to the syntax sweep - update the paths quoted in the Lab042 specification and the verifier agent definition This also defuses the import-time work finding without touching 41 files: the labs still create directories and write files on import, but nothing imports them now except the gate, which does so deliberately. Gate passes: syntax clean, protocol imports, 15 lab modules import, 2 functional suites run. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
153 lines
4.3 KiB
Python
153 lines
4.3 KiB
Python
"""
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Lab002, часть 2.
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Повреждение одного бита пакета без контроля целостности.
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Цель:
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1. Сформировать цифровой пакет.
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2. Намеренно изменить один бит полезной нагрузки.
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3. Разобрать повреждённый пакет.
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4. Убедиться, что без CRC повреждение не обнаруживается.
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"""
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import struct
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# ============================================================
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# Константы протокола
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# ============================================================
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SYNC_WORD = 0xAA55
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PROTOCOL_VERSION = 1
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MESSAGE_TYPE_TEXT = 1
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HEADER_FORMAT = ">HBBHH"
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# ============================================================
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# Формирование исходного пакета
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# ============================================================
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message = "ПРИВЕТ SDR"
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payload = message.encode("utf-8")
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sequence_number = 1
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message_type = MESSAGE_TYPE_TEXT
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payload_length = len(payload)
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header = struct.pack(
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HEADER_FORMAT,
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SYNC_WORD,
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PROTOCOL_VERSION,
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message_type,
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sequence_number,
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payload_length,
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)
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packet = header + payload
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print("Исходное сообщение:")
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print(message)
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print("\nИсходный пакет:")
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print(packet.hex(" "))
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# ============================================================
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# Имитация повреждения пакета
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# ============================================================
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# bytes нельзя изменять напрямую.
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# Поэтому преобразуем пакет в изменяемый массив bytearray.
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corrupted_packet = bytearray(packet)
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header_size = struct.calcsize(HEADER_FORMAT)
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# В строке "ПРИВЕТ SDR":
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#
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# "ПРИВЕТ" занимает 12 байтов UTF-8,
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# пробел занимает 1 байт,
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# буква S находится по индексу 13 внутри PAYLOAD.
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payload_byte_index = 13
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# Полный индекс внутри пакета:
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packet_byte_index = header_size + payload_byte_index
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original_byte = corrupted_packet[packet_byte_index]
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# XOR с 0x01 изменяет младший бит:
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#
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# 0x53 = 01010011 = S
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# 0x52 = 01010010 = R
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corrupted_packet[packet_byte_index] ^= 0x01
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corrupted_byte = corrupted_packet[packet_byte_index]
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print("\nИзменяемый байт внутри пакета:")
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print(
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f"До повреждения: "
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f"{original_byte:3d} "
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f"= 0x{original_byte:02X} "
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f"= {original_byte:08b}"
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)
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print(
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f"После повреждения: "
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f"{corrupted_byte:3d} "
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f"= 0x{corrupted_byte:02X} "
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f"= {corrupted_byte:08b}"
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)
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print("\nПовреждённый пакет:")
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print(bytes(corrupted_packet).hex(" "))
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# ============================================================
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# Разбор повреждённого пакета
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# ============================================================
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received_header = corrupted_packet[:header_size]
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received_payload = corrupted_packet[header_size:]
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(
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received_sync,
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received_version,
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received_type,
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received_sequence,
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received_length,
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) = struct.unpack(HEADER_FORMAT, received_header)
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# ============================================================
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# Проверки структуры
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# ============================================================
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assert received_sync == SYNC_WORD
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assert received_version == PROTOCOL_VERSION
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assert received_type == MESSAGE_TYPE_TEXT
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assert received_sequence == sequence_number
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assert received_length == len(received_payload)
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print("\nВсе проверки заголовка пройдены.")
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restored_message = bytes(received_payload).decode("utf-8")
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print("\nСообщение после повреждения:")
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print(restored_message)
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print("\nИсходное сообщение:")
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print(message)
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# ============================================================
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# Проверка результата эксперимента
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# ============================================================
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assert restored_message != message
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print("\nПовреждение данных произошло.")
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print("Но заголовок и длина пакета остались правильными.")
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print("Без CRC приёмник не смог определить ошибку.") |