michael@0: #!/usr/bin/env python
michael@0: # Copyright (c) 2012 The Chromium Authors. All rights reserved.
michael@0: # Use of this source code is governed by a BSD-style license that can be
michael@0: # found in the LICENSE file.
michael@0: 
michael@0: """Extracts a single file from a CAB archive."""
michael@0: 
michael@0: import os
michael@0: import shutil
michael@0: import subprocess
michael@0: import sys
michael@0: import tempfile
michael@0: 
michael@0: def run_quiet(*args):
michael@0:   """Run 'expand' supressing noisy output. Returns returncode from process."""
michael@0:   popen = subprocess.Popen(args, stdout=subprocess.PIPE)
michael@0:   out, _ = popen.communicate()
michael@0:   if popen.returncode:
michael@0:     # expand emits errors to stdout, so if we fail, then print that out.
michael@0:     print out
michael@0:   return popen.returncode
michael@0: 
michael@0: def main():
michael@0:   if len(sys.argv) != 4:
michael@0:     print 'Usage: extract_from_cab.py cab_path archived_file output_dir'
michael@0:     return 1
michael@0: 
michael@0:   [cab_path, archived_file, output_dir] = sys.argv[1:]
michael@0: 
michael@0:   # Expand.exe does its work in a fixed-named temporary directory created within
michael@0:   # the given output directory. This is a problem for concurrent extractions, so
michael@0:   # create a unique temp dir within the desired output directory to work around
michael@0:   # this limitation.
michael@0:   temp_dir = tempfile.mkdtemp(dir=output_dir)
michael@0: 
michael@0:   try:
michael@0:     # Invoke the Windows expand utility to extract the file.
michael@0:     level = run_quiet('expand', cab_path, '-F:' + archived_file, temp_dir)
michael@0:     if level == 0:
michael@0:       # Move the output file into place, preserving expand.exe's behavior of
michael@0:       # paving over any preexisting file.
michael@0:       output_file = os.path.join(output_dir, archived_file)
michael@0:       try:
michael@0:         os.remove(output_file)
michael@0:       except OSError:
michael@0:         pass
michael@0:       os.rename(os.path.join(temp_dir, archived_file), output_file)
michael@0:   finally:
michael@0:     shutil.rmtree(temp_dir, True)
michael@0: 
michael@0:   if level != 0:
michael@0:     return level
michael@0: 
michael@0:   # The expand utility preserves the modification date and time of the archived
michael@0:   # file. Touch the extracted file. This helps build systems that compare the
michael@0:   # modification times of input and output files to determine whether to do an
michael@0:   # action.
michael@0:   os.utime(os.path.join(output_dir, archived_file), None)
michael@0:   return 0
michael@0: 
michael@0: 
michael@0: if __name__ == '__main__':
michael@0:   sys.exit(main())