1 """

     2 Move a file in the safest way possible::

     3 

     4     >>> from django.core.files.move import file_move_safe

     5     >>> file_move_safe("/tmp/old_file", "/tmp/new_file")

     6 """

     7 

     8 import os

     9 from django.core.files import locks

    10 

    11 try:

    12     from shutil import copystat

    13 except ImportError:

    14     import stat

    15     def copystat(src, dst):

    16         """Copy all stat info (mode bits, atime and mtime) from src to dst"""

    17         st = os.stat(src)

    18         mode = stat.S_IMODE(st.st_mode)

    19         if hasattr(os, 'utime'):

    20             os.utime(dst, (st.st_atime, st.st_mtime))

    21         if hasattr(os, 'chmod'):

    22             os.chmod(dst, mode)

    23 

    24 __all__ = ['file_move_safe']

    25 

    26 def _samefile(src, dst):

    27     # Macintosh, Unix.

    28     if hasattr(os.path,'samefile'):

    29         try:

    30             return os.path.samefile(src, dst)

    31         except OSError:

    32             return False

    33 

    34     # All other platforms: check for same pathname.

    35     return (os.path.normcase(os.path.abspath(src)) ==

    36             os.path.normcase(os.path.abspath(dst)))

    37 

    38 def file_move_safe(old_file_name, new_file_name, chunk_size = 1024*64, allow_overwrite=False):

    39     """

    40     Moves a file from one location to another in the safest way possible.

    41 

    42     First, tries ``os.rename``, which is simple but will break across filesystems.

    43     If that fails, streams manually from one file to another in pure Python.

    44 

    45     If the destination file exists and ``allow_overwrite`` is ``False``, this

    46     function will throw an ``IOError``.

    47     """

    48 

    49     # There's no reason to move if we don't have to.

    50     if _samefile(old_file_name, new_file_name):

    51         return

    52 

    53     try:

    54         os.rename(old_file_name, new_file_name)

    55         return

    56     except OSError:

    57         # This will happen with os.rename if moving to another filesystem

    58         # or when moving opened files on certain operating systems

    59         pass

    60 

    61     # first open the old file, so that it won't go away

    62     old_file = open(old_file_name, 'rb')

    63     try:

    64         # now open the new file, not forgetting allow_overwrite

    65         fd = os.open(new_file_name, os.O_WRONLY | os.O_CREAT | getattr(os, 'O_BINARY', 0) |

    66                                     (not allow_overwrite and os.O_EXCL or 0))

    67         try:

    68             locks.lock(fd, locks.LOCK_EX)

    69             current_chunk = None

    70             while current_chunk != '':

    71                 current_chunk = old_file.read(chunk_size)

    72                 os.write(fd, current_chunk)

    73         finally:

    74             locks.unlock(fd)

    75             os.close(fd)

    76     finally:

    77         old_file.close()

    78     copystat(old_file_name, new_file_name)

    79 

    80     try:

    81         os.remove(old_file_name)

    82     except OSError, e:

    83         # Certain operating systems (Cygwin and Windows) 

    84         # fail when deleting opened files, ignore it.  (For the 

    85         # systems where this happens, temporary files will be auto-deleted

    86         # on close anyway.)

    87         if getattr(e, 'winerror', 0) != 32 and getattr(e, 'errno', 0) != 13:

    88             raise