40 lines
879 B
Python
40 lines
879 B
Python
#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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from binascii import hexlify
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from struct import unpack
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import sys
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FILE = sys.argv[1]
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print("Opening {}".format(FILE))
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csum_pre = 0
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csum = 0
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last_byte = 0xff
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with open(FILE, "rb") as f:
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while True:
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block = f.read(1024)
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for c in block:
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csum_pre = csum
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csum += c
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csum &= 0xff
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if len(block) < 1024:
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print("End reached.")
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last_byte = unpack("B", block[-1:])[0]
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break
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print("Sum of all bytes: {:02x}".format(csum))
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if csum == 0:
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print("CHECKSUM VALID.")
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else:
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print("CHECKSUM INVALID!!! (Or GCD or other type.)")
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#print("Sum without last: {:02x}".format(csum_pre))
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expected_cksum = ( 0x100 - csum_pre ) & 0xff
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print("Expected last byte: {:02x}".format(expected_cksum))
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print("Actual last byte: {:02x}".format(last_byte))
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