34 lines
876 B
Python
34 lines
876 B
Python
#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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"""
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Adds up all bytes from the beginning of a file and shows where
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a byte in the file matches the expected checksum at that location.
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"""
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from grmn import ChkSum
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import sys
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FILE = sys.argv[1]
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BLOCKSIZE = 4096
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OFFSET = 0x0
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csum = ChkSum()
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prev_remainder = b"\x00"
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print("Reading {} ...".format(FILE))
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with open(FILE, "rb") as f:
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while True:
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start_pos = f.tell()
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block = f.read(BLOCKSIZE)
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block = block[OFFSET:]
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for i in range(0, len(block)):
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c = block[i:i+1]
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exp = bytes([csum.get_expected()])
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if c == exp:
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print("Found matching 0x{:02x} at 0x{:x} ({:x} + {:d}).".format(c[0], OFFSET + start_pos + i, OFFSET, start_pos + i))
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csum.add(bytes(c))
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if len(block) < BLOCKSIZE:
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break
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#break
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f.close()
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