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"""firmware_file
The firmware_file module is responsible for handling a firmware file.
"""
# IMPORT
import sys
import os
from blue_st_sdk.utils.number_conversion import LittleEndian
# CLASSES
[docs]class STM32Crc32(object):
"""Computes the CRC32 by using the same algorithm implemented by STM32 chips.
The algorithm works on unsigned integer 32 numbers, hence the buffer must
have a length multiple of 4.
"""
INITIAL_VALUE = 0xffffffff
"""Initial value of the CRC."""
CRC_TABLE = [
0x00000000, 0x04C11DB7, 0x09823B6E, 0x0D4326D9,
0x130476DC, 0x17C56B6B, 0x1A864DB2, 0x1E475005,
0x2608EDB8, 0x22C9F00F, 0x2F8AD6D6, 0x2B4BCB61,
0x350C9B64, 0x31CD86D3, 0x3C8EA00A, 0x384FBDBD]
"""Nibble lookup table for 0x04C11DB7 polynomial."""
[docs] def __init__(self):
"""Constructor."""
self.reset()
def _urs(self, value, n):
"""Getting the Unsigned Right Shift operation.
E.g.:
a >>> b
Python does not provide a built-in operator for this, so here it is
simulated. This assumes integers are 32 bits long.
"""
return (value % 0x100000000) >> n
def _crc32_fast(self, crc, data):
"""Fast CRC at 32 bits.
Apply all 32-bits.
Process 32-bits, 4 at a time, or 8 rounds.
Assumes 32-bit reg, masking index to 4-bits.
0x04C11DB7 Polynomial used in STM32 chips.
"""
crc = crc ^ data
crc = ((crc << 4) & 0xffffffff) ^ self.CRC_TABLE[self._urs(crc, 28)]
crc = ((crc << 4) & 0xffffffff) ^ self.CRC_TABLE[self._urs(crc, 28)]
crc = ((crc << 4) & 0xffffffff) ^ self.CRC_TABLE[self._urs(crc, 28)]
crc = ((crc << 4) & 0xffffffff) ^ self.CRC_TABLE[self._urs(crc, 28)]
crc = ((crc << 4) & 0xffffffff) ^ self.CRC_TABLE[self._urs(crc, 28)]
crc = ((crc << 4) & 0xffffffff) ^ self.CRC_TABLE[self._urs(crc, 28)]
crc = ((crc << 4) & 0xffffffff) ^ self.CRC_TABLE[self._urs(crc, 28)]
crc = ((crc << 4) & 0xffffffff) ^ self.CRC_TABLE[self._urs(crc, 28)]
return crc
[docs] def get_value(self):
"""Get the CRC value.
Returns:
int: The value of the current CRC.
"""
return self._current_crc
[docs] def update(self, data):
"""Update the value of the CRC.
Size of data in bytes must be multiple of 4.
Args:
data (bytearray): Data to compute the CRC value of.
Raises:
:exc:`ValueError` if the length of the data is not multiple of 4.
"""
if len(data) % 4 != 0:
raise ValueError('Size of data to compute the CRC on must be \
multiple of 4 [bytes].')
for i in range(0, len(data), 4):
tmp = LittleEndian.bytes_to_int32(data, i * 4)
self._current_crc = self._crc32_fast(self._current_crc, tmp)
[docs] def reset(self):
"""Reset the CRC to the initial value."""
self._current_crc = self.INITIAL_VALUE