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      1 #!/usr/bin/env python
      2 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
      3 # Use of this source code is governed by a BSD-style license that can be
      4 # found in the LICENSE file.
      5 
      6 """Extracts a single file from a CAB archive."""
      7 
      8 import os
      9 import shutil
     10 import subprocess
     11 import sys
     12 import tempfile
     13 
     14 def run_quiet(*args):
     15   """Run 'expand' suppressing noisy output. Returns returncode from process."""
     16   popen = subprocess.Popen(args, stdout=subprocess.PIPE)
     17   out, _ = popen.communicate()
     18   if popen.returncode:
     19     # expand emits errors to stdout, so if we fail, then print that out.
     20     print out
     21   return popen.returncode
     22 
     23 def main():
     24   if len(sys.argv) != 4:
     25     print 'Usage: extract_from_cab.py cab_path archived_file output_dir'
     26     return 1
     27 
     28   [cab_path, archived_file, output_dir] = sys.argv[1:]
     29 
     30   # Expand.exe does its work in a fixed-named temporary directory created within
     31   # the given output directory. This is a problem for concurrent extractions, so
     32   # create a unique temp dir within the desired output directory to work around
     33   # this limitation.
     34   temp_dir = tempfile.mkdtemp(dir=output_dir)
     35 
     36   try:
     37     # Invoke the Windows expand utility to extract the file.
     38     level = run_quiet('expand', cab_path, '-F:' + archived_file, temp_dir)
     39     if level == 0:
     40       # Move the output file into place, preserving expand.exe's behavior of
     41       # paving over any preexisting file.
     42       output_file = os.path.join(output_dir, archived_file)
     43       try:
     44         os.remove(output_file)
     45       except OSError:
     46         pass
     47       os.rename(os.path.join(temp_dir, archived_file), output_file)
     48   finally:
     49     shutil.rmtree(temp_dir, True)
     50 
     51   if level != 0:
     52     return level
     53 
     54   # The expand utility preserves the modification date and time of the archived
     55   # file. Touch the extracted file. This helps build systems that compare the
     56   # modification times of input and output files to determine whether to do an
     57   # action.
     58   os.utime(os.path.join(output_dir, archived_file), None)
     59   return 0
     60 
     61 
     62 if __name__ == '__main__':
     63   sys.exit(main())
     64