LaMont Jones
20 years ago
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74466badde
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#!/usr/bin/env python
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# Copyright Paul Sladen <code@paul.sladen.org>, 2005-05-14
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# You may use this work under the terms of the GNU GPL.
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#
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# Synopsis:
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# 1. call dumpe2fs /dev/xxxx | grep -E '^( Free blocks: |Block size:)'
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# 2. decode Block size, eg. 4096 bytes
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# 3. decode ranges of Free blocks, like: 123, 132-145, 149-150, 167
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# 4. open '/dev/xxxx' for writing
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# 5. seek to each location (block_number * block_size) and write lots of NUL
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# 6. profit
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"""\
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e2fszero 0.1 (2005-05-14)
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Usage: e2fs-zero [-h] [-v] [-w|-n] ext2-filesystem
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Zero unused blocks in an Ext2 Filesystem, to increase compression and rsyncability.
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-h --help this message
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-v --verbose extra information
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-n --dryrun disable writing to the filesystem
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-w --write enable writing to the filesystem (default)
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Note: This program relies on 'dumpe2fs' to do the dangerous calculations!
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NOTE: YES, THIS PROGRAM REALLY WILL OVERWRITE (bits of) YOUR FILESYSTEM WITH NULLS\
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"""
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DUMPE2FS = '/sbin/dumpe2fs'
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import os, sys
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# messages
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verbose = False
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# enable writing operations
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dangerous = False
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def main():
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global verbose, dangerous, DUMPE2FS
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# catch people who need usage help
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# this is the worst and more incorrect piece of code in here
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leftover = []
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for fight in sys.argv[1:]:
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if fight == '-v' or fight == '--verbose':
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verbose = True
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continue
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elif fight == '-n' or fight == '--dryrun':
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dangerous = False
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continue
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elif fight == '-w' or fight == '--write':
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dangerous = True
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continue
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elif fight[0] == '-':
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print __doc__
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sys.exit()
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leftover.append(fight)
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#print `leftover`
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try:
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if len(leftover) != 1:
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raise 'ArgumentError'
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filesystem = leftover[0]
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if len(filesystem) <= 0:
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raise 'NoFilesystemName'
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except:
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print >> sys.stderr, __doc__
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sys.exit()
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# We need access to the filesystem image (either a block device or a very large file)
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# and we also need to have 'dumpe2fs', otherwise we can't open a pipe() from it.
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try:
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stat = os.stat(filesystem)
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stat = os.stat(DUMPE2FS)
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# Might aswell just let the user see any stderr errors from dumpe2fs,
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# although annoying it prints a banner first
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#out, err = os.popen3("%s '%s'" % (DUMPE2FS, filesystem))[1:]
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sys.stderr.write('calling ')
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pipe = os.popen("%s '%s'" % (DUMPE2FS, filesystem))
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except OSError:
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print >> sys.stderr, "$(PROGRAM): can't access $(filesystem), try --help"
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# We're looking for the following lines from dumpe2fs, in order, and ignoring the rest:
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# Filesystem volume name: <none>
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# Free blocks: 134859
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# Block size: 4096
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# Free blocks: 1123, 1345-1456, 1567, 1678-1789
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# Free blocks: 2123-2345, 2456-2567, 2678, 2789
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s = pipe.readline()
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if s <= 'Filesystem volume name:':
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raise "Failed to parse correct dumpe2fs output"
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# 'Free blocks:'
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while not s.startswith('Free blocks:') and len(s) > 0:
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s = pipe.readline()
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try:
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free_blocks = int(s.strip().split(': ')[1])
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except:
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raise "Failed to parse unused block count ('Free blocks:')"
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if verbose:
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print "Detected filsystem contains %d free blocks" % (free_blocks)
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# 'Block size:'
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while not s.startswith('Block size:') and len(s) > 0:
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s = pipe.readline()
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try:
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block_size = int(s.strip().split(': ')[1])
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except:
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raise "Failed to parse filesystem block-size ('Block size:')"
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if verbose:
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print "Detected filsystem block_size = %d bytes" % (block_size)
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# 'Free blocks:' (multiple entries, one per Ext2 "group")
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free_ranges = []
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while True:
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while len(s) and not s.startswith(' Free blocks:'):
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try:
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s = pipe.readline()
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except:
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raise "failed to read"
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# Detect EOF
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if not len(s):
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break
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#print len(s), `s`
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# Strip the label: and separate the commas
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try:
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#print `s.strip()`
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free_ranges += s.split(': ', 1)[1].strip().split(', ')[:]
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except:
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print >> sys.stderr, `s`
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raise "Failed to parse free_ranges (' Free blocks:')"
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s = pipe.readline()
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#print `free_ranges`
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# Turn the strings into integer lists of useful free blocks
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# 'blocks' contains each free blocks and get _very_ big
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# 'wipes' contains [offset, length] pairs
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record_blocks = False
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record_wipes = True
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blocks = []
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wipes = []
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free_block_count = 0
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for egg in free_ranges:
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if len(egg) > 0:
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# Assuming this ext2 group has some spare space in it...
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try:
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# Find some ranges (Ranges are inclusive, eg. 172-184)
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if egg.find('-') > 0:
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#blocks += range(*map(int, egg.split('-')))
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a, b = egg.split('-')
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if record_blocks: blocks += range(int(a), int(b) + 1)
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if record_wipes: wipes.append([block_size * int(a), block_size * (int(b) - int(a) + 1)])
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free_block_count += int(b) - int(a) + 1
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# But some are singular (eg. '199') is just one free block on its own
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else:
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if record_blocks: blocks += [int(egg)]
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if record_wipes: wipes.append([block_size * int(egg), block_size])
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free_block_count += 1
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except:
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# since we're nearly at the point of writing to the disk,
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# it probably better to just safely roll over and die
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print "Bzzzz on trying to decode " + `egg`
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blocks.sort()
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#print len(blocks), `blocks`
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if verbose:
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print len(wipes), 'offset/length pairs', `wipes`
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if verbose or free_blocks != free_block_count:
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print "Free blocks; parsed: %d, decoded: %d" % (free_blocks, free_block_count)
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if free_blocks != free_block_count:
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raise 'Decoded Free blocks do not match count in filesystem!'
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perform_wipe(filesystem, wipes)
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WRITE_SIZE = 2**18
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PADDING = '\0'
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# fstream file-access [open/f.write/f.tell] seems to have some
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# grave funnyiness that causes the file to be randomly truncated.
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# Since I spent a good while tearing my hair out over this, I've
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# changed it to just use the normal POSIX os.open/os.write/close
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# Here we take the offset/length pairs decoded above, open the
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# ext2 filesystem image and overwrite the unused areas.
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# it would be handy to truncate areas (make them sparse) so that they
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# don't actually take up space on disk to...
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def perform_wipe(filename, wipes = [[0, 0]]):
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progress_counter = 0.0
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percentage = 100.0 / len(wipes)
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empty_space = PADDING * WRITE_SIZE
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#f = open(filename, 'w')
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if dangerous:
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mode = os.O_WRONLY|os.EX_CANTCREAT
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else:
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mode = os.O_RDONLY|os.EX_CANTCREAT
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fd = os.open(filename, mode)
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# Don't waste space on a tty, display a progress percentage instead.
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if sys.stdout.isatty():
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end = '\r'
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else:
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end = '\n'
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for offset, length in wipes:
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progress_counter += percentage
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sys.stdout.write("wiping position %16d for %16d bytes (%5.1f%%)%s" %
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(offset, length, progress_counter, end))
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#f.seek(offset)
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os.lseek(fd, offset, 0)
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#print 'currently at (before) ' + `f.tell()`
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#print 'currently at (before) ' + `os.tell(fd)`
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# only write 256kB at a time, since we can stick that in a buffer
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# and not have Python regenerate HUGE arrays each time
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if 1:
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while length >= WRITE_SIZE and length > 0:
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#f.write(empty_space)
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#length -= WRITE_SIZE
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if dangerous:
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length -= os.write(fd, empty_space)
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else:
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length -= WRITE_SIZE
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#f.write('\xaa' * length)
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#f.write('hello')
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if dangerous:
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os.write(fd, PADDING * length)
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#print 'currently at (after) ' + `f.tell()`
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#print 'currently at (after) ' + `os.tell(fd)`
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#f.close()
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os.close(fd)
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if sys.stdout.isatty():
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print
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if verbose:
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print 'All done! Hopefully your filesystem is not toast.'
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if __name__ == '__main__':
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main()
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