new_contents: #!/usr/bin/env python
  # Software License Agreement (BSD License)
  #
  # Copyright (c) 2009, Willow Garage, Inc.
  # All rights reserved.
  #
  # Redistribution and use in source and binary forms, with or without
  # modification, are permitted provided that the following conditions
  # are met:
  #
  #  * Redistributions of source code must retain the above copyright
  #    notice, this list of conditions and the following disclaimer.
  #  * Redistributions in binary form must reproduce the above
  #    copyright notice, this list of conditions and the following
  #    disclaimer in the documentation and/or other materials provided
  #    with the distribution.
  #  * Neither the name of Willow Garage, Inc. nor the names of its
  #    contributors may be used to endorse or promote products derived
  #    from this software without specific prior written permission.
  #
  # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  # FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  # COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  # INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  # BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  # LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  # CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  # ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  # POSSIBILITY OF SUCH DAMAGE.
  
  PKG = 'rosbag'
  import roslib; roslib.load_manifest(PKG)
  
  import optparse
  import os
  import shutil
  import sys
  
  import rosbag
  from rosbag import bag
  
  if __name__ == '__main__':
      parser = optparse.OptionParser(usage='slash.py [options] BAGFILE1 [BAGFILE2 ...]',
                                     description='Slash one or more bag files.')
  
      (options, args) = parser.parse_args(sys.argv[1:])
  
      if len(args) < 1:
          parser.error('You must specify at least one bag file.')
          
      for filename in args:
          b = rosbag.Bag(filename)
          index_pos = b._index_data_pos
          b.close()
  
          (root, ext) = os.path.splitext(filename)
          slash_filename = '%s.slash%s' % (root, ext)
  
          shutil.copy(filename, slash_filename)
          f = open(slash_filename, 'r+b')
          f.seek(b._file_header_pos)
          header = {
              'op':          bag._pack_uint8(bag._OP_FILE_HEADER),
              'index_pos':   bag._pack_uint64(0),
              'conn_count':  bag._pack_uint32(0),
              'chunk_count': bag._pack_uint32(0)
          }
          bag._write_record(f, header, padded_size=bag._FILE_HEADER_LENGTH)
          f.truncate(index_pos / 100)
          f.close()
          
          print '%s slashed.' % slash_filename
          
          (root, ext) = os.path.splitext(filename)
          reindex_filename = '%s.reindex%s' % (root, ext)
          shutil.copy(slash_filename, reindex_filename)
  
          bv = rosbag.Bag(slash_filename, allow_unindexed=True)
          version = bv.version
          bv.close()
  
          if version == 102:
              b = rosbag.Bag(slash_filename, allow_unindexed=True)
  
              reindexed = rosbag.Bag(reindex_filename, 'w')
  
              b.reindex()
  
              try:
                  for (topic, msg, t) in b.read_messages():
                      print topic, t
                      reindexed.write(topic, msg, t)
              except:
                  pass
              reindexed.close()
  
              b.close()
          else:
              try:
                  b = rosbag.Bag(reindex_filename, 'a', allow_unindexed=True)
              except Exception, ex:
                  print str(ex)
              try:
                  b.reindex()
              except:
                  pass
              b.close()
  
subject: add debugging slash.py script