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"""
Move a file in the safest way possible::
>>> from django.core.files.move import file_move_safe
>>> file_move_safe("/tmp/old_file", "/tmp/new_file")
"""
import errno
import os
from shutil import copystat
from django.core.files import locks
__all__ = ['file_move_safe']
def _samefile(src, dst):
# Macintosh, Unix.
if hasattr(os.path, 'samefile'):
try:
return os.path.samefile(src, dst)
except OSError:
return False
# All other platforms: check for same pathname.
return (os.path.normcase(os.path.abspath(src)) ==
os.path.normcase(os.path.abspath(dst)))
def file_move_safe(old_file_name, new_file_name, chunk_size=1024 * 64, allow_overwrite=False):
"""
Moves a file from one location to another in the safest way possible.
First, tries ``os.rename``, which is simple but will break across filesystems.
If that fails, streams manually from one file to another in pure Python.
If the destination file exists and ``allow_overwrite`` is ``False``, this
function will throw an ``IOError``.
"""
# There's no reason to move if we don't have to.
if _samefile(old_file_name, new_file_name):
return
try:
# If the destination file exists and allow_overwrite is False then raise an IOError
if not allow_overwrite and os.access(new_file_name, os.F_OK):
raise IOError("Destination file %s exists and allow_overwrite is False" % new_file_name)
os.rename(old_file_name, new_file_name)
return
except OSError:
# This will happen with os.rename if moving to another filesystem
# or when moving opened files on certain operating systems
pass
# first open the old file, so that it won't go away
with open(old_file_name, 'rb') as old_file:
# now open the new file, not forgetting allow_overwrite
fd = os.open(new_file_name, (os.O_WRONLY | os.O_CREAT | getattr(os, 'O_BINARY', 0) |
(os.O_EXCL if not allow_overwrite else 0)))
try:
locks.lock(fd, locks.LOCK_EX)
current_chunk = None
while current_chunk != b'':
current_chunk = old_file.read(chunk_size)
os.write(fd, current_chunk)
finally:
locks.unlock(fd)
os.close(fd)
try:
copystat(old_file_name, new_file_name)
except OSError as e:
# Certain filesystems (e.g. CIFS) fail to copy the file's metadata if
# the type of the destination filesystem isn't the same as the source
# filesystem; ignore that.
if getattr(e, 'errno', 0) != errno.EPERM:
raise
try:
os.remove(old_file_name)
except OSError as e:
# Certain operating systems (Cygwin and Windows)
# fail when deleting opened files, ignore it. (For the
# systems where this happens, temporary files will be auto-deleted
# on close anyway.)
if getattr(e, 'winerror', 0) != 32 and getattr(e, 'errno', 0) != 13:
raise
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