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artizirk/stm32_crc32.py

Last active December 4, 2020 10:17
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stm32_crc32.py
def _slow_crc(data, seed=0xFFFF_FFFF, polynomial=0x04C11DB7):
"""
STM32 CRC that is actually CRC-32/MPEG2 but input data is read as litle-endian (not big-endian like MPEG)
"""
crc = seed
# Pad data if needed
pad_len = len(data) % 4
if pad_len > 0:
words = array.array('I', data[:-pad_len])
words.frombytes(data[-pad_len:] + b'\xff' * (4 - pad_len))
else:
words = array.array('I', data)
# CRC
for word in words:
crc ^= word
for i in range(32):
if crc & 0x80000000:
crc = (crc << 1) ^ polynomial
else:
crc = (crc << 1)
crc &= 0xFFFF_FFFF
return crc
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