mirror of
https://github.com/mjg59/python-broadlink.git
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46 lines
1.3 KiB
Python
46 lines
1.3 KiB
Python
"""Helper functions."""
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from ctypes import c_ushort
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import socket
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from .exceptions import exception
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def get_local_ip() -> str:
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"""Try to determine the local IP address of the machine."""
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# Useful for VPNs.
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try:
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local_ip_address = socket.gethostbyname(socket.gethostname())
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if not local_ip_address.startswith('127.'):
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return local_ip_address
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except socket.gaierror:
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raise exception(-4013) # DNS Error
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# Connecting to UDP address does not send packets.
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with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as s:
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s.connect(('8.8.8.8', 53))
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return s.getsockname()[0]
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def calculate_crc16(input_data: bytes) -> int:
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"""Calculate the CRC-16 of a byte string."""
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crc16_tab = []
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crc16_constant = 0xA001
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for i in range(0, 256):
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crc = c_ushort(i).value
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for j in range(0, 8):
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if crc & 0x0001:
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crc = c_ushort(crc >> 1).value ^ crc16_constant
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else:
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crc = c_ushort(crc >> 1).value
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crc16_tab.append(hex(crc))
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crcValue = 0xFFFF
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for c in input_data:
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tmp = crcValue ^ c
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rotated = c_ushort(crcValue >> 8).value
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crcValue = rotated ^ int(crc16_tab[(tmp & 0x00FF)], 0)
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return crcValue
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