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93 lines
3.3 KiB
Python
Executable File
93 lines
3.3 KiB
Python
Executable File
#!/usr/bin/env python3
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"""SIMH disk container trailer stripper
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Copyright (C) 2022 by Paul Koning
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Permission is hereby granted, free of charge, to any person obtaining a
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copy of this software and associated documentation files (the "Software"),
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to deal in the Software without restriction, including without limitation
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the rights to use, copy, modify, merge, publish, distribute, sublicense,
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and/or sell copies of the Software, and to permit persons to whom the
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Software is furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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Except as contained in this notice, the names of The Authors shall not be
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used in advertising or otherwise to promote the sale, use or other dealings
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in this Software without prior written authorization from the Authors.
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This program strips the "trailer" from Mark Pizzolato's version of SIMH from
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disk container files.
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To use it, run the script with the names of the containers to be
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stripped. Two switches may be included in the argument list; they
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take effect when seen, so typically you will want them at the start of
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the argument list:
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-q: don't print any messages
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-f: if a trailer is found, strip it without asking
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By default, messages are printed as to whether a trailer is seen or
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not, and if found, the user is prompted whether to strip it. In that
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prompt, the default answer is "no".
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"""
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import sys
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import io
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from zlib import crc32
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m1 = 0xffffffff
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force = quiet = False
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def zap (fn):
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with open (fn, "r+b") as f:
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l = f.seek (0, io.SEEK_END)
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if l < 8192:
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if not quiet:
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print (fn, "is too small to consider")
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return
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lastblk = f.seek (-512, io.SEEK_END)
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if lastblk % 512:
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if not quiet:
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print (fn, "is not a multiple of 512 bytes long")
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return
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tail = f.read (512)
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if not tail.startswith (b"simh"):
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if not quiet:
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print (fn, "last block does not start with 'simh'")
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return
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c1 = crc32 (tail[:508]) & m1
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c = int.from_bytes (tail[508:], "big")
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if c1 != c:
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print (fn, "trailer CRC does not match, {:0>8x} vs. {:0>8x}".format (c, c1))
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return
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if force or input ("{} strip trailer? ".format (fn)).lower ().startswith ("y"):
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f.truncate (lastblk)
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if not quiet:
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print ("trailer stripped from", fn)
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else:
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if not quiet:
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print (fn, "not changed")
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if __name__ == "__main__":
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args = sys.argv[1:]
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if not args:
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print ("usage: zap.py [-q] [-f] container ...")
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for fn in args:
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if fn == "-q":
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quiet = True
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continue
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if fn == "-f":
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force = True
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continue
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zap (fn)
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